NERVOUS SYSTEM
Topic: The divisions of the nervous system: central and peripheral (somatic
and autonomic).
PL
E
WHAT YOU NEED TO KNOW
1. Outline the structure (components) of the nervous system.
2. Outline the role of the nervous system, including:
a. Central nervous system (CNS)
i. Brain
ii. Spinal cord
b. Peripheral nervous system
i. Somatic nervous system
ii. Autonomic nervous system
1. Sympathetic nervous system
2. Parasympathetic nervous system
3. Identify similarities and differences between the components of the peripheral
nervous system and/or central nervous system
1. The nervous system
SA
M
The nervous system is divided into the two main components: 1) the central nervous
system (CNS) and 2) the peripheral nervous system (PNS). The nervous system has the
following structure:
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2a. The CNS – Brain and spinal cord
The CNS consists of the brain and the spinal cord. The brain provides conscious
awareness and is involved in all psychological processes. The brain consists of many
regions, which are responsible for different functions.
For example, the brain consists of
four main lobes: frontal lobe,
parietal lobe, temporal lobe and
occipital lobe.
PL
E
The occipital lobe processes visual
information; the temporal lobe
processes auditory information;
the parietal lobe integrates
information from the different
senses and therefore plays an
important
role
in
spatial
navigation; the frontal lobe is
associated
with
higher-order
functions, including planning,
abstract reasoning and logic.
SA
M
The brain stem connects the brain and spinal cord and controls involuntary processes,
including our heartbeat, breathing and consciousness.
The role of the spinal cord is to transfer messages to and from the brain, and the rest
of the body. The spinal cord is also responsible for simple reflex actions that do not
involve the brain, for example jumping out of your chair if you sit on a drawing pin.
2a. The PNS – somatic and autonomic nervous systems
The role of the peripheral nervous system (PNS) is to relay messages (nerve impulses)
from the CNS (brain and spinal cord) to the rest of the body. The PNS consists of two
main components: 1) the somatic nervous system and 2) the autonomic nervous
system.
The somatic nervous system facilitates communication between the CNS and the
outside world. The somatic nervous system is made up of sensory receptors that carry
information to the spinal cord and brain, and motor pathways that allow the brain to
control movement. Therefore, the role of the somatic nervous system is to carry
sensory information from the outside world to the brain and provide muscle responses
via the motor pathways.
The autonomic nervous system plays an important role in homeostasis, which
maintains internal processes like body temperature, heart rate and blood pressure.
The autonomic nervous system only consists of motor pathways and has two
components: 1) the sympathetic nervous system and 2) the parasympathetic nervous
system.
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The sympathetic nervous system is typically involved in responses that prepare the
body for fight or flight. Impulses travel from the sympathetic nervous system to
organs in the body to help us prepare for action when we are faced with a dangerous
situation. For example, our heart rate, blood pressure and breathing rate increase,
while less important functions like digestion, salivation and the desire to urinate are
suppressed.
The role of the parasympathetic nervous system is to relax the body, and return us to
our ‘normal’ resting state. Consequently, the parasympathetic nervous system slows
down our heart rate and breathing rate, and reduces our blood pressure. Furthermore,
any functions that were previously slowed down during a fight or flight reaction are
started again (e.g. digestion).
E
SA
M
SPINAL CORD
PL
BRAIN
CENTRAL NERVOUS SYSTEM
SIMILARITIES
DIFFERENCES
The brain stem and spinal The brain provides conscious
cord both control involuntary awareness and allows for
processes (e.g. the brain higher-order thinking, while the
stem controls breathing and spinal cord allows for simple
the spinal cord controls reflex responses.
involuntary reflexes).
The brain consists of multiple
regions responsible for different
functions, whereas the spinal
cord has one main function.
SOMATIC
AUTONOMIC
SYMPATHETIC /
PARASYMPATHETIC
PERIPHERAL NERVOUS SYSTEM
SIMILARITIES
DIFFERENCES
The sympathetic nervous The autonomic nervous system
system
(part
of
the consists
of
two
subautonomic nervous system) components, whereas the
and the somatic nervous somatic nervous system only
system respond to external has one.
stimuli. The sympathetic
nervous system responds to The somatic nervous system
external stimuli by preparing has
sensory
and
motor
the body for fight or flight pathways,
whereas
the
and the somatic nervous autonomic nervous system only
system responds to external has motor pathways.
stimuli
(by
carrying
information from sensory The autonomic nervous system
receptors to the spinal cord controls internal organs and
and brain).
glands, while the somatic
nervous
system
controls
muscles and movement.
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Possible Exam Questions
1. Which of the following statements is false?
The autonomic nervous system: a) comprises of two subsystems; b) controls
communication between the CNS and the environment; c) plays an important role
in homeostasis; d) maintains internal processes like blood pressure. (1 mark)
2. Joline has just been to the cinema with her friend to watch a new horror movie.
While she is walking home alone she believes that she can hear footsteps following
her and starts to panic. Without thinking she starts sprinting and gets home as fast
as she can. She bursts through the front door, heart pounding, dripping with sweat
and shaking.
E
Outline the role of the autonomic nervous system and central nervous system,
referring to Joline’s experience in your answer. (4 marks)
PL
3. Outline the role of the central nervous system/somatic nervous system/autonomic
nervous system. (4 marks each)
SA
M
4. Outline two differences in the organisation/function of the somatic nervous system
and autonomic nervous system. (4 marks)
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NEURONS & NEUROTRANSMISSION
Topic: The structure and function of sensory, relay and motor neurons. The
process of synaptic transmission, including reference to neurotransmitters,
excitation and inhibition.
E
WHAT YOU NEED TO KNOW
1. Outline the structure and function of:
a. Sensory neurons
b. Relay neurons
c. Motor neurons
2. Outline the process of synaptic transmission and explain the difference between:
a. Excitation
b. Inhibition
1. Sensory, relay and motor neurons
PL
There are three main types of neurons, including: sensory, relay and motor. Each of
these neurons has a different function, depending on its location in the body and its
role within the nervous system.
SA
M
Note: All three types of neuron consist of similar parts, however their structure,
location and function are different and this is what you need be aware of.
SENSORY
RELAY
MOTOR
Sensory neurons are found in receptors such as the eyes, ears, tongue and skin, and
carry nerve impulses to the spinal cord and brain. When these nerve impulses reach
the brain, they are translated into ‘sensations’, such as vision, hearing, taste and
touch. However, not all sensory neurons reach the brain, as some neurons stop at the
spinal cord, allowing for quick reflex actions.
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Relay neurons are found between sensory input and motor output/response. Relay
neurons are found in the brain and spinal cord and allow sensory and motor neurons
to communicate.
Motor neurons are found in the central nervous system (CNS) and control muscle
movements. When motor neurons are stimulated they release neurotransmitters that
bind to the receptors on muscles to trigger a response, which lead to movement.
PL
E
As you can see from the diagrams above, all three neurons consist of similar parts. The
dendrites receive signals from other neurons or from sensory receptor cells. The
dendrites are typically connected to the cell body, which is often referred to as the
‘control centre’ of the neuron, as it’s contains the nucleus. The axon is a long slender
fibre that carries nerve impulses, in the form of an electrical signal known as action
potential, away from the cell body towards the axon terminals, where the neuron
ends. Most axons are surrounded by a myelin sheath (except for relay neurons) which
insulates the axon so that the electrical impulses travel faster along the axon. The axon
terminal connects the neuron to other neurons (or directly to organs), using a process
called synaptic transmission.
2. Synaptic transmission
SA
M
Information is passed down the axon of the neuron as an electrical impulse known as
action potential. Once the action potential reaches the end of the axon it needs to be
transferred to another neuron or tissue. It must cross over a gap between the presynaptic neuron and post-synaptic neuron – which is known as the synaptic gap. At the
end of the neuron (in the axon terminal) are the synaptic vesicles which contains
chemical messengers, known as neurotransmitters. When the electrical impulse
(action potential) reaches these synaptic vesicles, they release their contents of
neurotransmitters.
Neurotransmitters
then
carry the signal across the
synaptic gap. They bind to
receptor sites on the postsynaptic cell that then
become activated. Once the
receptors
have
been
activated,
they
either
produce
excitatory
or
inhibitory effects on the
post-synaptic cell.
Some neurotransmitters are
excitatory and some are inhibitory. Excitatory neurotransmitters (e.g. noradrenaline)
make the post-synaptic cell more likely to fire, whereas inhibitory neurotransmitters
(e.g. GABA) make them less likely to fire. For example, if an excitatory
neurotransmitter like noradrenaline binds to the post-synaptic receptors it will cause
an electrical charge in the cell membrane which results in an excitatory post-synaptic
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potential (EPSP), which makes the post-synaptic cell more likely to fire. Whereas, if an
inhibitory neurotransmitter like GABA binds to the post-synaptic receptors it will result
in an inhibitory post-synaptic potential (IPSP), which makes the post-synaptic cell less
likely to fire.
Possible Exam Questions
1. Complete the following sentence (1 mark): Motor neurons…
a. are found in receptor cells
b. carry nerve impulses to the brain
c. are found between the brain and spinal cord
d. are found in the central nervous system
2. Briefly outline the process of synaptic transmission. (4 marks)
E
3. Outline two differences between sensory neurons and motor neurons. (4 marks)
SA
M
PL
4. Jack is 8-years-old and has recently been prescribed Ritalin to help with his ADHD.
Jack’s mother searches for Ritalin on the internet and learns that Ritalin elevates
the level of dopamine, which is an excitatory neurotransmitter. Outline the role of
excitatory neurotransmitters, referring to Jack in your answer. (4 marks).
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THE ENDOCRINE SYSTEM
Topic: The function of the endocrine system: glands and hormones.
WHAT YOU NEED TO KNOW
1. Outline the function of the endocrine system, including:
a. Glands
b. Hormones
Exam Hint: For this part of the course it is important to know what hormones are
released by the different glands in the body and what effect these hormones have.
1. The Endocrine System - Glands
E
The endocrine system works alongside the nervous system. It is a network of glands
across the body that secrete chemical messages called hormones. Instead of using
nerves (sensory and motor neurons) to transmit information, this system uses blood
vessels. Different hormones produce different effects (behaviours).
SA
M
PL
The glands which make up the endocrine system can be found in the diagram below.
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Each gland produces a different hormone. The word ‘hormone’ comes from the Greek
work ‘hormao’ which means ‘excite’, as hormones excite (stimulate) a particular part
of the body.
2. The Endocrine System - Hormones
The hypothalamus is connected to the pituitary gland and is responsible for
stimulating or controlling the release of hormones from the pituitary gland. Therefore,
the hypothalamus is the control system which regulates the endocrine system.
SA
M
PL
E
The pituitary gland is sometimes known as the master gland because the hormones
released by the pituitary gland control and stimulate the release of hormones from
other glands in the endocrine system. The pituitary gland is also divided into the
anterior (front) and posterior (rear)
lobes (see right), which release
different hormones. A key hormone
released from the posterior lobe is
oxytocin (often referred to as the
‘love hormone’) which is responsible
for uterus contractions during
childbirth. A key hormone released
from the anterior lobe is
adrenocortical trophic hormone
(ACTH) which stimulates the adrenal
cortex and the release of cortisol,
during the stress response.
The main hormone released from
the pineal gland is melatonin, which
is responsible for important
biological rhythms, including the sleep-wake cycle.
The thyroid gland releases thyroxine which is responsible for regulating metabolism.
People who have a fast metabolism typically struggle to put on weight, as metabolism
is involved in the chemical process of converting food into energy.
The adrenal gland is divided into two parts, the adrenal medulla and the adrenal
cortex. The adrenal medulla is responsible for releasing adrenaline and noradrenaline,
which play a key role in the fight or flight response. The adrenal cortex releases
cortisol, which stimulates the release of glucose to provide the body with energy while
suppressing the immune system.
Males and females have different sex organs, and in males the testes release
androgens, which include the main hormone testosterone. Testosterone is responsible
for the development of male sex characteristics during puberty while also promoting
muscle growth. In females, the ovaries release oestrogen which controls the
regulation of the female reproductive system, including the menstrual cycle and
pregnancy.
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GLAND
MAIN HORMONE
RELEASED
EFFECT
Stimulates and controls the release of
hormones from the pituitary gland.
Hypothalamus
Stimulates the adrenal cortex and the
release of cortisol during the stress
response.
Posterior – oxytocin
Responsible for uterus contractions
during childbirth.
Pineal Gland
Melatonin
Responsible for important biological
rhythms, including the sleep-wake
cycle.
Thyroid Gland
Thyroxine
Responsible
metabolism.
Adrenal medulla –
adrenaline &
noradrenaline
The key hormones in the fight or flight
response.
Ovaries (female)
Testes (male)
regulating
Adrenal cortex cortisol
Stimulates the release of glucose to
provide the body with energy, while
suppressing the immune system.
Oestrogen
Controls the regulation of the female
reproductive system, including the
menstrual cycle and pregnancy
Testosterone
Responsible for the development of
male sex characteristics during
puberty, while also promoting muscle
growth.
SA
M
Adrenal Gland
for
PL
Pituitary Gland
(Master Gland)
E
Anterior adrenocortical trophic
hormone (ACTH)
Possible Exam Questions
1. Which of the following glands is responsible for the release of hormones from all
other glands within the endocrine system?
a. Thyroid
b. Adrenal
c. Hypothalamus
d. Pituitary
2. Identify one gland that forms part of the endocrine system and outline its function.
(2 marks)
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3. Outline the relationship between glands and hormones. (4 marks)
SA
M
PL
E
4. Describe the functions of the endocrine system. (6 marks)
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FIGHT OR FLIGHT
Topic: The fight or flight response, including the role of adrenaline.
WHAT YOU NEED TO KNOW
1. Outline and evaluate the fight or flight response, including the role of adrenaline.
The ‘Fight or Flight’ Response
When someone enters a potentially stressful situation, the amygdala (part of the
limbic system) is activated. The amygdala responds to sensory input (what we see,
hear, smell, etc.) and connects sensory input with emotions associated with the
fight or flight response (e.g. fear and anger).
PL
E
If the situation is deemed as stressful/dangerous, the amygdala sends a distress
signal to the hypothalamus, which communicates with the body through the
sympathetic nervous system. If the situation requires a short-term response the
sympathomedullary pathway (SAM pathway) is activated, triggering the fight or
flight response.
A person enters a stressful/dangerous situation.
SA
M
The amygdala (part of the limbic system) is activated which send a distress signal to
the hypothalamus.
The hypothalamus activates the sympathomedullary pathway (SAM pathway) – the
pathway running to the adrenal medulla and the sympathetic nervous system
(SNS).
The SNS stimulates the adrenal medulla, part of the adrenal gland.
The adrenal medulla secretes the hormones adrenaline and noradrenaline into the
bloodstream.
Adrenaline causes a number of physiological changes to prepare the body for fight
or flight.
Exam Hint: Adrenaline causes a number of physiological changes (e.g. increased heart
rate); however, it is important that you understand why these changes occur in
relation to the fight or flight response.
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PHYSIOLOGICAL CHANGE
Increased heart rate
REASON
To increase blood flow to organs and
increase the movement of adrenaline
around the body.
Increased breathing rate
To increase oxygen intake.
Pupil dilation
To increase light entry into the eye and
enhance vision (especially in the dark).
Sweat production
To regulate temperature.
E
Reduction
of
non-essential
To increase energy for other essential
functions (e.g. digestive system,
functions.
urination, salivation)
Evaluation
When faced with a dangerous situation our reaction is not limited to the fight or
flight response; some psychologists suggest that humans engage in an initial
‘freeze’ response. Gray (1988) suggests that the first response to danger is to avoid
confrontation altogether, which is demonstrated by a freeze response. During the
freeze response animals and humans are hyper-vigilant, while they appraise the
situation to decide the best course of action for that particular threat.
SA
M

PL
Following the fight or flight response, the parasympathetic nervous system is
activated to return the body back to its ‘normal’ resting state. Consequently, the
parasympathetic nervous system slows down our heart rate and breathing rate and
reduces our blood pressure. Furthermore, any functions that were previously slowed
down are started again (e.g. digestion).
The fight or flight response is typically a male response to danger and more recent
research suggests that females adopt a ‘tend and befriend’ response in
stressful/dangerous situations. According to Taylor et al. (2000), women are more
likely to protect their offspring (tend) and form alliances with other women
(befriend), rather than fight an adversary or flee. Furthermore, the fight or flight
response may be counterintuitive for women, as running (flight) might be seen as a
sign of weakness and put their offspring at risk of danger.
Exam Hint: It is possible to incorporate knowledge of the issues and debates in
psychology into your evaluation. For example, the above point is linked to the ‘Gender
Bias’ topic and therefore you could explore the ideas of androcentrism and beta bias
within this evaluation point.
 Early research into the fight or flight response was typically conducted on males
(androcentrism) and consequently, researchers assumed that the findings could be
generalised to females. This highlights a beta bias within this area of psychology as
psychologists assumed that females responded in the same way as males, until
Taylor provided evidence of a tend and befriend response.

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
While the fight or flight response may have been a useful survival mechanism for
our ancestors, who faced genuinely life-threatening situations (e.g. from
predators), modern day life rarely requires such an intense biological response.
Furthermore, the stressors of modern day life can repeatedly activate the fight or
flight response, which can have a negative consequence on our health. For
example, humans who face a lot of stress and continually activate the sympathetic
nervous system, continually increase their blood pressure which can cause damage
to their blood vessels and heart disease. This suggests that the fight or flight
response is a maladaptive response in modern-day life.
Possible Exam Questions
PL
E
1. Which of the following responses is not caused by the activation of the
sympathetic nervous system?
a. Pupil dilation
b. Sweat production
c. Decreased digestion
d. Increased salivation
2. Outline the function of adrenaline in the fight-or-flight response. (4 marks)
SA
M
3. Lynn’s husband John works night shifts and she hates being at home alone. One
night she is suddenly woken by a crashing sound coming from the kitchen. With
her heart racing, she slowly walks into the kitchen, trembling and sweating with
fear. She turns on the light to see that her cat has knocked a plate off the kitchen
worktop. She picks up the cat and within minutes she is feeling much more relaxed.
Outline the fight or flight response, referring to the changes that occurred in Lynn
in the first minute and the changes that occurred after a few minutes. (4 marks)
4. Outline and evaluate the fight or flight response. (12/16 marks)
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LOCALISATION AND LATERALISATION
Specification: Localisation of function in the brain and hemispheric
lateralisation: motor, somatosensory, visual, auditory and language
centres; Broca’s and Wernicke’s areas, split brain research. Plasticity and
functional recovery of the brain after trauma.
DEFINITIONS
Localisation of function is the idea that certain
Localisation of Function
functions (e.g. language, memory, etc.) have certain
locations within the brain.
Lateralisation is the fact that the two halves of the
brain are functionally different and that each
Hemispheric Lateralisation hemisphere has functional specialisations, e.g. the left
is dominant for language, and the right excels at visual
motor tasks.
The motor area is responsible for voluntary
Motor Area
movements by sending signals to the muscles in the
body.
The somatosensory area receives incoming sensory
Somatosensory Area
information from the skin to produce sensations
related to pressure, pain, temperature, etc.
The visual area receives and processes visual
information. The visual area contains different parts
Visual Area
that process different types of information including
colour, shape or movement.
The auditory area is responsible for analysing and
Auditory Area
processing acoustic information.
The Broca’s area is found in the left frontal lobe and is
Broca’s Area
thought to be involved in language production.
The Wernicke’s area is found in the left temporal lobe
Wernicke’s Area
and is thought to be involved in language
processing/comprehension.
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SA
M
KEY TERMS
PL
E
WHAT YOU NEED TO KNOW
1. Outline and evaluate what research has shown about localisation of function in
the brain, with reference to the following regions:
a. Motor area
b. Somatosensory area
c. Visual area
d. Auditory area
2. Outline the role of language centres in the brain, including:
a. Broca’s area
b. Wernicke’s area
3. Outline and evaluate research into lateralisation and/or the split brain.
4. Outline and evaluate evidence for plasticity and/or functional recovery of the
brain after trauma.
Split-Brain Research
Plasticity
Functional Recovery
Split-brain patients are individuals who have
undergone a surgical procedure where the corpus
callosum, which connects the two hemispheres, is cut.
Brain plasticity refers to the brain’s ability to change
and adapt because of experience.
Functional recovery is the transfer of functions from a
damaged area of the brain after trauma to other
undamaged areas.
Introduction – Localisation of Brain Function
E
Localisation of function is the idea that certain functions (e.g. language, memory, etc.)
have certain locations or areas within the brain. This idea has been supported by
recent neuroimaging studies, but was also examined much earlier, typically using case
studies.
SA
M
PL
One such case study is that of Phineas Gage, who in 1848 while working on a rail line,
experienced a drastic accident in which a piece of iron went through his skull. Although
Gage survived this ordeal, he did experience a change in personality, such as loss of
inhibition and anger. This change provided evidence to support the theory of
localisation of brain function, as it was believed that the area the iron stake damaged
was responsible for personality.
There are four key areas that you
need to be aware of: motor,
somatosensory,
visual
and
auditory areas.
1a. Motor Area
The motor area is located in the
frontal lobe and is responsible for
voluntary movements by sending
signals to the muscles in the body.
Hitzig and Fritsch (1870) first
discovered that different muscles
are coordinated by different areas
of the motor cortex by electrically stimulating the motor area of dogs. This resulted in
muscular contractions in different areas of the body depending on where the probe
was inserted. The regions of the motor area are arranged in a logical order, for
example, the region that controls finger movement is located next to the region that
controls the hand and arm and so on.
1b. Somatosensory Area
The somatosensory area is located in the parietal lobe and receives incoming sensory
information from the skin to produce sensations related to pressure, pain,
temperature, etc. Different parts of the somatosensory area receive messages from
different locations of the body. Robertson (1995) found that this area of the brain is
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highly adaptable, with Braille readers having larger areas in the somatosensory area
for their fingertips compared to normal sighted participants.
1c. Visual Area
At the back of the brain, in the occipital lobe is the visual area, which receives and
processes visual information. Information from the right-hand side visual field is
processed in the left hemisphere, and information from the left-hand side visual field
is processed in the right hemisphere. The visual area contains different parts that
process different types of information including colour, shape or movement.
1d. Auditory Area
SA
M
PL
E
The auditory area is located in the temporal lobe and is responsible for analysing and
processing acoustic information. Information from the left ear goes primarily to the
right hemisphere and information from the right ear goes primarily to the left
hemisphere. The auditory area contains different parts, and the primary auditory area
is involved in processing simple features of sound, including volume, tempo and pitch.
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2a. Language Centres: Broca’s Area
The Broca’s area is named after Paul Broca, who discovered this region while treating
a patient named Leborgne, who was more commonly referred to as ‘Tan’. Tan could
understand spoken language but was unable to produce any coherent words, and
could only say ‘Tan’.
PL
E
After Tan’s death, Broca
conducted
a
post-mortem
examination on Tan’s brain and
discovered that he had a lesion
in the left frontal lobe. This led
Broca to conclude that this area
was responsible for speech
production.
People
with
damage to this area experience
Broca’s aphasia, which results
in slow and inarticulate speech.
SA
M
Extension:
Due
to
the
significance of this finding,
Dronkers et al. (2007) decided to conduct an MRI scan on Tan’s brain, to try to confirm
Broca’s original work. Although there was a lesion found in Broca’s area, they also
found evidence to suggest that other areas may have also contributed to the failure in
speech production. Therefore it is likely that the Broca’s area is not solely responsible
for speech production, as other areas may also play a role.
2b. Language Centres: Wernicke’s Area
At a similar time, Carl Wernicke discovered another area of the brain that was involved
in understanding language. Wernicke found that patients with lesions to Wernicke’s
area were still able to speak, but were unable to comprehend language.
Wernicke’s area is found in the left temporal lobe, and it is thought to be involved in
language processing/comprehension. People with damage to this area struggle to
comprehend language, often producing sentences that are fluent, but meaningless
(Wernicke’s aphasia).
Wernicke concluded that language involves a separate motor and sensory region. The
motor region is located in Broca’s area, and the sensory region is located in Wernicke’s
area.
Extension: However, research by Saygin et al. (2003) found that some patients
displayed symptoms of Wernicke’s aphasia without any damage to this area. This
suggests that language comprehension is much more complex than originally thought.
Further evidence has also been found which suggests some left-handed people process
language in the right hemisphere.
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LOCATION
Frontal
Lobe
SOMATOSENSORY
AREA
Parietal
Lobe
PL
Occipital
Lobe
The visual area receives and
processes visual
information. The visual area
contains different parts that
process different types of
information including
colour, shape or movement.
SA
M
VISUAL AREA
The motor area is
responsible for voluntary
movements by sending
signals to the muscles in the
body.
The somatosensory area
receives incoming sensory
information from the skin to
produce sensations related
to pressure, pain,
temperature, etc.
LEFT, RIGHT OR BOTH
HEMISPHERES
Both
The motor area on one
side of the brain controls
the muscles on the
opposite side.
Both
The somatosensory area
on one side of the brain
receives sensory
information from the
opposite side of the body.
Both
Information from the
right-hand side visual field
is processed in the left
hemisphere, and
information from the lefthand side visual field is
processed in the right
hemisphere.
Both
Information from the left
ear goes primarily to the
right hemisphere and
information from the right
ear goes primarily to the
left hemisphere.
E
MOTOR
AREA
FUNCTION
AUDITORY
AREA
Temporal
Lobe
BROCA’S
AREA
Left
Frontal
Lobe
WERNICKE’S
AREA
Left
Temporal
Lobe
The auditory area is
responsible for analysing
and processing acoustic
information.
The Broca’s area is found in
the left frontal lobe and is
thought to be involved in
language production.
The Wernicke’s area is
found in the left temporal
lobe and is thought to be
involved in language
comprehension.
Left
Left
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Evaluating Localisation of Function
The claim that functions are localised to certain areas of the brain has been
criticised. Lashley proposed the equipotentiality theory, which suggests that the
basic motor and sensory functions are localised, but that higher mental functions
are not. He claimed that intact areas of the cortex could take over responsibility for
specific cognitive functions following brain injury. This therefore casts doubt on
theories about the localisation of functions, suggesting that functions are not
localised to just one region, as other regions can take over specific functions
following brain injury.

There is a wealth of case studies on patients with damage to Broca’s and
Wernicke’s areas that have demonstrated their functions. For example, Broca’s
aphasia is an impaired ability to produce language; in most cases, this is caused by
brain damage in Broca’s area. Wernicke’s aphasia is an impairment of language
perception, demonstrating the important role played by this brain region in the
comprehension of language.
o However, although there is evidence from case studies to support the
function of the Broca’s area and Wernicke’s area, more recent research has
provided contradictory evidence. Dronkers et al. (2007) conducted an MRI
scan on Tan’s brain, to try to confirm Broca’s findings. Although there was a
lesion found in Broca’s area, they also found evidence to suggest other
areas may have contributed to the failure in speech production. These
results suggest that the Broca’s area may not be the only region responsible
for speech production and the deficits found in patients with Broca’s
aphasia could be the result of damage to other neighbouring regions.
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

Furthermore, psychologists suggest that it is more important to investigate how
the brain areas communicate with each other, rather than focusing on specific
brain regions. Wernicke claimed that although the different areas of the brain are
independent, they must interact with each other in order to function. An example
to demonstrate this is a man who lost his ability to read, following damage to the
connection between the visual cortex and the Wernicke’s area, which was reported
by Dejerine. This suggests that interactions between different areas produce
complex behaviours such as language. Therefore, damage to the connection
between any two points can result in impairments that resemble damage to the
localised brain region associated with that specific function. This reduces the
credibility of the localisation theory.
o Also, critics argue that theories of localisation are biologically
reductionist in nature and try to reduce very complex human
behaviours and cognitive processes to one specific brain region. Such
critics suggest that a more thorough understanding of the brain is
required to truly understand complex cognitive processes like language.

Finally, some psychologists argue that the idea of localisation fails to take into
account individual differences. Herasty (1997) found that women have
proportionally larger Broca’s and Wernicke’s areas than men, which can perhaps
explain the greater ease of language use amongst women. This, however, suggests
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a level of beta bias in the theory: the differences between men and woman are
ignored, and variations in the pattern of activation and the size of areas observed
during various language activities are not considered.
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3. Hemispheric Lateralisation
Lateralisation is the idea that the two halves of the brain are functionally different and
that each hemisphere has functional specialisations, e.g. the left is dominant for
language, and the right excels at visual motor tasks. The two hemispheres are
connected through nerve fibres called the corpus callosum, which facilitate
interhemispheric communication: allowing the left and right hemispheres to ‘talk to’
one another.
Split-Brain Research
Sperry and Gazzaniga (1967) were the first to investigate hemispheric lateralisation
with the use of split-brain patients.
E
Background: Split-brain patients are individuals who have undergone a surgical
procedure where the corpus callosum, which connects the two hemispheres, is cut. This
procedure, which separates the two hemispheres, was used as a treatment for severe
epilepsy.
PL
Aim: The aim of their research was to examine the extent to which the two
hemispheres are specialised for certain functions.
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Method: An image/word is projected to the patient’s left visual field (which is
processed by the right hemisphere) or the right visual field (which is processed by the
left hemisphere). When information is presented to one hemisphere in a split-brain
patient, the information is not transferred to the other hemisphere (as the corpus
callosum is cut).
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Sperry and Gazzaniga conducted many different experiments, including describe what
you see tasks, tactile tests, and drawing tasks.
 In the describe what you see task, a picture was presented to either the left or
right visual field and the participant had to simply describe what they saw.

In the tactile test, an object was placed in the patient’s left or right hand and they
had to either describe what they felt, or select a similar object from a series of
alternate objects.

Finally, in the drawing task, participants were presented with a picture in either
their left or right visual field, and they had to simply draw what they saw.
Findings:
DESCRIBE WHAT YOU SEE
TACTILE TESTS
The patient could not describe what was
shown and often reported that there was
nothing present.
PL
The patient could describe what they
saw, demonstrating the superiority of
the left hemisphere when it comes to
language production.
Picture presented to the left visual field
(processed by right hemisphere)
E
Pictured presented to the right visual field
(processed by left hemisphere)
Objects placed in the right hand
(processed by the left hemisphere)
The patient could not describe what they
felt and could only make wild guesses.
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The patient could describe verbally what
they felt. Or they could identify the test
object presented in the right hand (left
hemisphere), by selecting a similar
appropriate object, from a series of
alternate objects.
Objects placed in the left hand
(processed by the right hemisphere)
DRAWING TASKS
Pictured presented to the right visual field
(processed by left hemisphere)
While the right-hand would attempt to
draw a picture, the picture was never as
clear as the left hand, again
demonstrating the superiority of the
right hemisphere for visual motor tasks.
However, the left hand could identify a
test object presented in the left hand
(right hemisphere), by selecting a similar
appropriate object, from a series of
alternate objects.
Picture presented to the left visual field
(processed by right hemisphere)
The left-hand (controlled by the right
hemisphere) would consistently draw
clearer and better pictures than the righthand (even though all the participants
were right-handed).
This demonstrates the superiority of the
right hemisphere when it comes to visual
motor tasks.
Conclusion: The findings of Sperry and Gazzaniga’s research highlights a number of key
differences between the two hemispheres. Firstly, the left hemisphere is dominant in
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terms of speech and language. Secondly, the right hemisphere is dominant in terms of
visual-motor tasks.
Evaluating Split-Brain Research
It is assumed that the main advantage of brain lateralisation is that it increases
neural processing capacity (the ability to perform multiple tasks
simultaneously). Rogers et al. (2004) found that in a domestic chicken, brain
lateralisation is associated with an enhanced ability to perform two tasks
simultaneously (finding food and being vigilant for predators). Using only one
hemisphere to engage in a task leaves the other hemisphere free to engage in
other functions. This provides evidence for the advantages of brain
lateralisation and demonstrates how it can enhance brain efficiency in
cognitive tasks.
o However, because this research was carried out on animals, it is
impossible to conclude the same of humans. Unfortunately, much of the
research into lateralisation is flawed because the split-brain procedure
is rarely carried out now, meaning patients are difficult to come by.
Such studies often include very few participants, and often the research
takes an idiographic approach. Therefore, any conclusions drawn are
representative only of those individuals who had a confounding physical
disorder that made the procedure necessary. This is problematic as such
results cannot be generalised to the wider population.

Furthermore, research has suggested that lateralisation changes with age.
Szaflarki et al. (2006) found that language became more lateralised to the left
hemisphere with increasing age in children and adolescents, but after the age
of 25, lateralisation decreased with each decade of life. This raises questions
about lateralisation, such as whether everyone has one hemisphere that is
dominant over the other and whether this dominance changes with age.
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

Finally, it could be argued that language may not be restricted to the left
hemisphere. Turk et al. (2002) discovered a patient who suffered damage to the
left hemisphere but developed the capacity to speak in the right hemisphere,
eventually leading to the ability to speak about the information presented to either
side of the brain. This suggests that perhaps lateralisation is not fixed and that the
brain can adapt following damage to certain areas.
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4. Plasticity and Functional Recovery
The brain is not a static organ, and the functions and processes of the brain can change
as a result of experience and injury. Brain plasticity refers to the brain’s ability to
change and adapt because of experience. Research has demonstrated that the brain
continues to create new neural pathways and alter existing ones in response to
changing experiences (see evidence below).
The brain also appears to show evidence of functional recovery: the transfer of
functions from a damaged area of the brain after trauma to other undamaged areas. It
can do this through a process termed neuronal unmasking where ‘dormant’ synapses
(which have not received enough input to be active) open connections to compensate
for a nearby damaged area of the brain. This allows new connections in the brain to be
activated, thus recovering any damage occurring in specific regions.
Kuhn et al. found a significant increase in grey matter in various regions of the
brain after participants played video games for 30 minutes a day over a two-month
period. Similarly, Davidson et al. demonstrated the permanent change in the brain
generated by prolonged meditation: Buddhist monks who meditated frequently
had a much greater activation of gamma waves (which coordinate neural activity)
than did students with no experience of meditation. These two studies highlight
the idea of plasticity and the brain’s ability to adapt as a result of new experience,
whether it’s video games or mediation.
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
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Evidence/Evaluation for Plasticity and Functional Recovery

There is further research to support the notion of brain plasticity. Maguire et al.
found that the posterior hippocampal volume of London taxi drivers’ brains was
positively correlated with their time as a taxi driver and that there were significant
differences between the taxi drivers’ brains and those of controls. This shows that
the brain can permanently change in response to frequent exposure to a particular
task.
o However, some psychologists suggest that research investigating the
plasticity of the brain is limited. For example, Maguire’s research is
biologically reductionist and only examines a single biological factor (the
size of the hippocampus) in relation to spatial memory. This approach is
limited and fails to take into account all of the different
biological/cognitive processes involved in spatial navigation which may
limit our understanding. Other psychologists suggest that a holistic
approach to understanding complex human behaviour may be more
appropriate.

There is research to support the claim for functional recovery. Taijiri et al. (2013)
found that stem cells provided to rats after brain trauma showed a clear
development of neuron-like cells in the area of injury. This demonstrates the ability
of the brain to create new connections using neurons manufactured by stem cells.

While there is evidence for functional recovery, it is possible that this ability can
deteriorate with age. Elbert et al. concluded that the capacity for neural
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reorganisation is much greater in children than in adults, meaning that neural
regeneration is less effective in older brains. This may explain why adults find
change more demanding than do young people. Therefore, we must consider
individual differences when assessing the likelihood of functional recovery in the
brain after trauma.
A final strength of research examining plasticity and functional recovery is the
application of the findings to the field of neurorehabilitation. Understanding the
processes of plasticity and functional recovery led to the development of
neurorehabilitation which uses motor therapy and electrical stimulation of the
brain to counter the negative effects and deficits in motor and cognitive functions
following accidents, injuries and/or strokes. This demonstrates the positive
application of research in this area to help improve the cognitive functions of
people suffering from injuries.
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Possible Exam Questions
1. Explain what is meant by the term plasticity. (2 marks)
2. Briefly explain how split-brain patients could be examined in an experiment. (4
marks)
3. Briefly explain what split-brain research has shown. (4 marks)
4. Outline evidence in relation to brain plasticity. (4 marks)
5. Outline evidence in relation to functional recovery. (4 marks)
patients
to
investigate
hemispheric
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6. Evaluate research using split-brain
lateralisation of function. (4 marks)
PL
7. David is fourteen years old. Last year, he was hit by a bus when walking to school
and suffered from serious head injuries. While David made a full physical recovery,
he has problems with his speech and comprehension of language. However, after
one year, David had recovered nearly all of his language abilities. Use your
knowledge of functional recovery and plasticity to explain David’s recovery. (4
marks)
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8. Joseph suffered a stroke when he was 45-years-old. He could move his left arm and
leg but was paralysed down his right side. While Joseph could understand what
was said to him, he was unable to speak. Referring to Joseph, discuss hemispheric
lateralisation of language centres in the brain. (16 marks).
9. Describe and evaluate what research has shown about localisation of function in
the brain. (16 marks)
10. Describe and evaluate research into lateralisation and/or the split brain (16 marks).
11. Discuss evidence for plasticity and/or functional recovery after trauma. (16 marks)
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STUDYING THE BRAIN
Specification: Ways of studying the brain: scanning techniques, including
functional magnetic resonance imaging (fMRI); electroencephalogram
(EEGs) and event-related potentials (ERPs); post-mortem examinations.
WHAT YOU NEED TO KNOW
1. Outline and evaluate fMRI as a way of studying the brain
2. Outline and evaluate EEG & ERP as a way of studying the brain
3. Outline and evaluate post-mortem examinations as a way of studying the brain
4. Compare the different ways of studying the brain
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Electroencephalogram
(EEGs)
DEFINITIONS
Functional magnetic resonance imaging (fMRI) is a
brain-scanning technique that measures blood flow in
the brain when a person performs a task. fMRI works
on the premise that neurons in the brain which are the
most active (during a task), use the most energy. An
fMRI creates a dynamic (moving) 3D map of the brain,
highlighting which areas are involved in different
neural activities.
An electroencephalogram (EEG) works on the premise
that information is processed in the brain as electrical
activity in the form of action potentials or nerve
impulses, transmitted along neurons. EEG ners
measure this electrical activity through electrodes
attached to the scalp. Small electrical charges that are
detected by the electrodes are graphed over a period
of time, indicating the level of activity in the brain.
Event-Related Potentials (ERP) use similar equipment
to EEG, i.e. electrodes attached to the scalp. However,
the key difference is that a stimulus is presented to a
participant (for example a picture/sound) and the
researcher looks for activity related to that stimulus.
A post-mortem examination is when researchers study
the physical brain of a person who displayed a
particular behaviour while they were alive that
suggested possible brain damage. An example of this
technique is the work of Broca, who examined the
brain of a man who displayed speech problems when
he was alive. It was subsequently discovered that he
had a lesion in the area of the brain important for
speech production. This area later became known as
Broca’s area.
PL
KEY TERMS
Functional Magnetic
Resonance Imaging (fMRI)
Event-Related Potentials
(ERPs)
Post-Mortem Examination
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Introduction – Studying the Brain
Studying the brain allows psychologists to gain important insights into the
underlying foundations of our behaviour and mental processes. A range of
methods are available that involve scanning the living brain, and looking at
patterns of electrical activity. However, a post-mortem examination is another
possible approach.
1. Functional Magnetic Resonance Imaging (fMRI)
E
Functional magnetic resonance imaging
(fMRI) is a brain-scanning technique that
measures blood flow in the brain when a
person performs a task. fMRI works on
the premise that neurons in the brain
that are the most active during a task
use the most energy.
PL
Energy requires glucose and oxygen.
Oxygen is carried in the bloodstream
attached to haemoglobin (found in red
blood cells) and is released for use by
these active neurons, at which point the haemoglobin becomes deoxygenated.
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Deoxygenated haemoglobin has a different magnetic quality from oxygenated
haemoglobin. An fMRI can detect these different magnetic qualities and can be
used to create a dynamic (moving) 3D map of the brain, highlighting which areas
are involved in different neural activities. fMRI images show activity approximately
1-4 seconds after it occurs and are thought to be accurate within 1-2 mm. An
increase in blood flow is a response to the need for more oxygen in that area of
the brain when it becomes active, suggesting an increase in neural activity.
Evaluation of fMRI

Invasive or Non-Invasive: An advantage of fMRI is that is non-invasive. Unlike
other scanning techniques, for example Positron Emission Tomography (PET), fMRI
does not use radiation or involve inserting instruments directly into the brain, and
is therefore virtually risk-free. Consequently, this should allow more
patients/participants to undertake fMRI scans which could help psychologists to
gather further data on the functioning human brain and therefore develop our
understanding of localisation of function.

Spatial Resolution: fMRI scans have good spatial resolution. Spatial resolution
refers to the smallest feature (or measurement) that a scanner can detect, and is
an important feature of brain scanning techniques. Greater spatial resolution
allows psychologists to discriminate between different brain regions with greater
accuracy. fMRI scans have a spatial resolution of approximately 1-2 mm which is
significantly greater than the other techniques (EEG, ERP, etc.) Consequently,
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psychologists can determine the activity of different brain regions with greater
accuracy when using fMRI, in comparison to when using EEG and/or ERP.
Temporal Resolution: fMRI scans have poor temporal resolution. Temporal
resolution refers to the accuracy of the scanner in relation of time: or how quickly
the scanner can detect changes in brain activity. fMRI scans have a temporal
resolution of 1-4 seconds which is worse than other techniques (e.g. EEG/ERP
which have a temporal resolution of 1-10 milliseconds). Consequently,
psychologists are unable to predict with a high degree of accuracy the onset of
brain activity.

Causation: fMRI scans do not provide a direct measure of neural activity. fMRI
scans simply measure changes in blood flow and therefore it is impossible to infer
causation (at a neural level). While any change in blood flow may indicate activity
within a certain brain area, psychologists are unable to conclude whether this brain
region is associated with a particular function.
o In addition, some psychologists argue that fMRI scans can only show
localisation of function within a particular area of the brain, but are limited
in showing the communication that takes place among the different areas
of the brain, which might be critical to neural functioning.
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2. Electroencephalogram & Event-Related Potentials
Electroencephalogram (EEG)
PL
E
An electroencephalogram (EEG)
works on the premise that
information is processed in the
brain as electrical activity in the
form of action potentials or nerve
impulses,
transmitted
along
neurons. EEG scanners measure this
electrical
activity
through
electrodes attached to the scalp.
Small electrical charges detected by
the electrodes are graphed over a
period of time, indicating the level of activity in the brain. There are four types of
EEG patterns including alpha waves, beta waves, theta waves and delta waves.
Each of these patterns has two basic properties that psychologists can examine:
1. Amplitude: the intensity or size of the activity
2. Frequency: the speed or quantity of activity
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Also, EEG patterns produce two distinctive states: synchronised and
desynchronized patterns. A synchronised pattern is where a recognised waveform
(alpha, beta, delta and theta) can be detected, whereas a desynchronized is where
no pattern can be detected.
Fast desynchronized patterns are usually found when awake and synchronised
patterns are typically found during sleep (alpha waves are associated with light
sleep, and theta/delta waves are associated with deep sleep). Furthermore, EEG
scanning was responsible for developing our understanding of REM (dream) sleep,
which is associated with a fast, desynchronized activity, indicative of dreaming.
EEG can also be used to detect illnesses like epilepsy and sleep disorders, and to
diagnose other disorders that affect brain activity, like Alzheimer’s disease.
Event-Related Potentials (ERP)
Event-Related Potentials (ERP) use similar equipment to EEG, electrodes attached
to the scalp. However, the key difference is that a stimulus is presented to a
participant (for example a picture/sound) and the researcher looks for activity
related to that stimulus. However, as ERPs are difficult to separate from all of the
background EEG data, the stimulus is present many times (usually hundreds), and
an average response is graphed. This procedure, which is called ‘averaging’,
reduces any extraneous neural activity which makes the specific response to the
stimulus stand out.
The time or interval between the presentation of the stimulus and the response is
referred to as latency. ERPs have a very short latency and can be divided into two
broad categories. Waves (responses) that occur within 100 milliseconds following
the presentation of a stimulus are referred to as sensory ERPs, as they reflect a
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sensory response to the stimulus. ERPs that occur after 100 milliseconds are
referred to as cognitive ERPs, as they demonstrate some information processing.
Evaluation of EEG & ERP
Invasive or Non-Invasive: An advantage of EEG and ERP is that both techniques are
non-invasive. Unlike other scanning techniques, such as Positron Emission
Tomography (PET), EEG and ERP do not use radiation or involve inserting
instruments directly into the brain and are therefore virtually risk-free.
Furthermore, EEG and ERP are much cheaper techniques in comparison with fMRI
scanning and are therefore more readily available. Consequently, this should allow
more patients/participants to undertake EEG/ERPs, which could help psychologists
to gather further data on the functioning human brain and therefore develop our
understanding of different psychological phenomena, such as sleeping, and
different disorders like Alzheimer's.

Spatial Resolution: However, one disadvantage of EEG/ERP is that these
techniques have poor spatial resolution. Spatial resolution refers to the smallest
feature (or measurement) that a scanner can detect, and is an important feature of
brain scanning techniques. Greater spatial resolution allows psychologists to
discriminate between different brain regions with greater accuracy. EEGs/ERPs
only detect the activity in superficial regions of the brain. Consequently, EEGs and
ERPs are unable to provide information on what is happening in the deeper regions
of the brain (such as the hypothalamus), making this technique limited in
comparison to the fMRI, which has a spatial resolution of 1-2mm.
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

Temporal Resolution: An advantage of the EEG/ERP technique is that it has
good temporal resolution: it takes readings every millisecond, meaning it can
record the brain’s activity in real time as opposed to looking at a passive brain.
This leads to an accurate measurement of electrical activity when undertaking
a specific task.
o However, it could be argued that EEG/ERP is uncomfortable for the
participant, as electrodes are attached to the scalp. This could result in
unrepresentative readings as the patient’s discomfort may be affecting
cognitive responses to situations. fMRI scans, on the other hand, are
less invasive and would not cause the participants any discomfort,
leading to potentially more accurate recordings.

EEG: Another issue with EEG is that electrical activity is often detected in
several regions of the brain simultaneously. Consequently, it can be difficult
pinpoint the exact area/region of activity, making it difficult for researchers to
draw accurate conclusions.

ERP: However, ERPs enable the determination of how processing is affected by
a specific experimental manipulation. This makes ERP use a more
experimentally robust method as it can eliminate extraneous neutral activity,
something that other scanning techniques (and EEG) may struggle to do.
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3. Post-Mortem Examination
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The final method of investigating the brain is
post-mortem examination, where researchers
will study the physical brain of a person who
displayed a particular behaviour while they
were alive that suggested possible brain
damage. An example of this technique is the
work of Broca, who examined the brain of a
man who displayed speech problems when he
was alive. It was subsequently discovered
that he had a lesion in the area of the brain
important for speech production. This later
became known as Broca’s area. Similarly,
Wernicke discovered a region in the left
temporal lobe, which is important for
language comprehension and processing,
which is now known as Wernicke’s area.
This method of investigation has successfully contributed to the understanding of
many disorders. Iverson examined the brains of deceased schizophrenic patients and
found that they all had a higher concentration of dopamine, especially in the limbic
system, compared with brains of people without schizophrenia, highlighting the
importance of such investigations.
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Furthermore, post-mortem studies allow for a more detailed examination of
anatomical and neurochemical aspects of the brain than would be possible with other
techniques. They also enable researchers to examine deeper regions of the brain such
as the hypothalamus and hippocampus, something that is not as easy with other
methods of investigation.
Evaluation of Post-Mortem Examination

Causation: One of the main limitations of post-mortem examination is the issue of
causation. The deficit a patient displays during their lifetime (e.g. an inability to
speak) may not be linked to the deficits found in the brain (e.g. a damaged Broca’s
area). The deficits reported could have been the result of another illness, and
therefore psychologists are unable to conclude that the deficit is caused by the
damage found in the brain.
o In additional, another issue is that there are many extraneous factors that
can affect the results/conclusions of post-mortem examinations. For
example, people die at different stages of their life and for a variety of
different reasons. Furthermore, any medication a person may have been
taking, their age, and the length of time between death and post-mortem
examination, are all confounding factors that make the conclusions of such
research questionable.

However, one strength of post-mortem examinations is that they provide a
detailed examination of the anatomical structure and neurochemical aspects of
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the brain that is not possible with other scanning techniques (e.g. EEG, ERP and
fMRI). Post-mortem examinations can access areas like the hypothalamus and
hippocampus, which other scanning techniques cannot, and therefore provide
researchers with an insight into these deeper brain regions, which often provide a
useful basis for further research. For example, Iverson found a higher
concentration of dopamine in the limbic system of patients with schizophrenia
which has prompted a whole area of research looking into the neural correlates of
this disorder.
While post-mortem examinations are ‘invasive’, this is not an issue because the
patient is dead. However, there are ethical issues in relation to informed consent
and whether or not a patient provides consent before his/her death. Furthermore,
many post-mortem examinations are carried out on patients with severe
psychological deficits (e.g. patient HM who suffered from severe amnesia) who
would be unable to provide fully informed consent, and yet a post-mortem
examination has been conducted on his brain. This raises severe ethical questions
surrounding the nature of such investigations.
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INVASIVE OR
NON-INVASIVE
TEMPORAL
RESOLUTION
SPATIAL
RESOLUTION
fMRI
fMRI measures blood flow when a
person performs a task and creates
a dynamic (moving) 3D map of the
brain, highlighting which areas are
involved in different neural
activities.
Non-Invasive
1-4 s
1-2 mm
EEG
EEG measures electrical activity
through electrodes attached to the
scalp. Small electrical charges are
detected by the electrodes that are
graphed over a period of time,
indicating the level of activity in the
brain.
Non-Invasive
(although
uncomfortable)
ERP uses similar equipment to EEG.
However, the key difference is that
a stimulus is presented to a
participant and the researcher
looks for activity related to that
stimulus.
Non-Invasive
(although
uncomfortable)
1-10
ms
Superficial
general
regions only
A post-mortem examination is
when researchers study the
physical brain of a person who
displayed a particular behaviour
while they were alive that
suggested possible brain damage.
N/A (Invasive although the
person is no
longer alive)
N/A
N/A
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TECHNIQUE
OUTLINE
ERP
4. Compare Ways of Studying the Brain
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Post-Mortem
Examination
1-10
ms
Superficial
general
regions only
Exam Hint: Questions 9 and 10 in the possible exam questions section are tricky, as
they require you to compare/contrast different ways of studying the brain. The table
above can help you find the similarities and differences between the different
techniques.
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Possible Exam Questions
1.
2.
3.
4.
Short Answer: Outline fMRI as a way of studying the brain. (4 marks)
Short Answer: Outline EEGs as a way of studying the brain. (4 marks)
Short Answer: Outline ERPs as a way of studying the brain. (4 marks)
Short Answer: Outline post-mortem examinations as a way of studying the brain.
(4 marks)
5.
6.
7.
8.
Short Answer: Outline one strength and one limitation of fMRI. (6 marks)
Short Answer: Outline one strength and one limitation of EEGs. (6 marks)
Short Answer: Outline one strength and one limitation of ERPs. (6 marks)
Short Answer: Outline one strength and one limitation of post-mortem
examinations. (6 marks)
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9. Short Answer: Outline one difference between EEG and ERP (2 marks)
10. Short Answer: Outline one difference between fMRI and EEG. (2 marks)
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11. Essay: Discuss ways of studying the brain. (16 marks)
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BIOLOGICAL RHYTHMS
Specification: Biological rhythms: circadian, infradian and ultradian and
the difference between these rhythms. The effect of endogenous
pacemakers and exogenous zeitgebers on the sleep/wake cycle.
WHAT YOU NEED TO KNOW
1. Outline examples of, and evaluate circadian rhythms, with research support.
2. Outline examples of, and evaluate the role of endogenous pacemakers and
exogenous zeitgebers.
3. Outline examples of, and evaluate infradian and/or ultradian rhythms
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Biological Rhythms
Circadian
DEFINITIONS
Biological rhythms are cyclical patterns within
biological systems that have evolved in response to
environmental influences, e.g. day and night. There are
two key factors that govern biological rhythms:
endogenous pacemakers (internal), the body’s
biological clocks, and exogenous zeitgebers (external),
which are changes in the environment.
One biological rhythm is the 24-hour circadian rhythm
(often known as the ‘body clock’), which is reset by
levels of light. The word circadian is from the Latin
‘circa’ which means ‘about’, and ‘dian’, which means
‘day’. Examples of circadian rhythms include the sleepwave cycle and body temperature.
Another important biological rhythm is infradian
rhythms, which last longer than 24 hours and can be
weekly, monthly or annually. A monthly infradian
rhythm is the female menstrual cycle, which is
regulated by hormones that either promote ovulation
or stimulate the uterus for fertilisation.
Ultradian rhythms last less than 24 hours and can be
found in the pattern of human sleep. This cycle
alternates between REM (rapid eye movement) and
NREM (non-rapid movement) sleep and consists of five
stages. The cycle starts at light sleep, progressing to
deep sleep and then into REM sleep, where brain
waves speed up and dreaming occurs. This repeats
itself about every 90 minutes throughout the night and
a person can experience up to five complete sleep
cycles each night.
Endogenous pacemakers are internal mechanisms that
govern biological rhythms, in particular the circadian
sleep/wake cycle. Although endogenous pacemakers
are internal biological clocks, they can be altered and
affected by the environment. The most important
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KEY TERMS
Infradian
Ultradian
Endogenous Pacemakers
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Exogenous Zeitgebers
endogenous pacemaker is the suprachiasmatic nucleus,
which is closely linked to the pineal gland, both of
which are influential in maintaining the circadian sleepwake cycle.
Exogenous zeitgebers influence biological rhythms.
These can be described as environmental events that
are responsible for resetting the biological clock of an
organism. They can include social cues, such as meal
times and social activities, but the most important
zeitgeber is light, which is responsible for resetting the
body clock each day, keeping it on a 24-hour cycle.
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Introduction
Biological rhythms are cyclical patterns within biological systems that have
evolved in response to environmental influences, e.g. day and night. There are two
key factors that govern biological rhythms: endogenous pacemakers (internal
factors), the body’s biological clocks, and exogenous zeitgebers (external factors),
which are changes in the environment.
Exam Hint: For each of the biological rhythms (circadian, infradian and ultradian)
it is important you that you can define the term and provide at least one
example.
1. Circadian Rhythms
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One biological rhythm is the 24-hour circadian rhythm (often known as the ‘body
clock’), which is reset by levels of light. The word circadian is from the Latin ‘circa’
which means ‘about’, and ‘dian’, which means ‘day’.
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The sleep-wake cycle is an example of a circadian rhythm, which dictates when
humans and animals should be asleep and awake. Light provides the primary input
to this system, acting as the external cue for sleeping or waking. Light is first
detected by the eye, which then sends messages concerning the level of
brightness to the suprachiasmatic nuclei (SCN). The SCN then uses this
information to coordinate the activity of the entire circadian system. Sleeping and
wakefulness are not determined by the circadian rhythm alone, but also by
homoeostasis. When an individual has been awake for a long time, homeostasis
tells the body that there is a need for sleep because of energy consumption. This
homeostatic drive for sleep increases throughout the day, reaching its maximum in
the late evening, when most people fall asleep.
Body temperature is another circadian rhythm. Human body temperature is at its
lowest in the early hours of the morning (36oC at 4:30 am) and at its highest in the
early evening (38oC at 6 pm). Sleep typically occurs when the core temperature
starts to drop, and the body temperature starts to rise towards the end of a sleep
cycle promoting feelings of alertness first thing in the morning.
Evaluating Circadian Rhythms
Research Support: Research has been conducted to investigate circadian
rhythms and the effect of external cues like light on this system. Siffre (1975)
found that the absence of external cues significantly altered his circadian
rhythm: When he returned from an underground stay with no clocks or light,
he believed the date to be a month earlier than it was. This suggests that his
24-hour sleep-wake cycle was increased by the lack of external cues, making
him believe one day was longer than it was, and leading to his thinking that
fewer days had passed.
o Siffre’s case study has been the subject of criticism. As the researcher
and sole participant in his case study, there are severe issues with
generalisability. However, further research by Aschoff & Weber (1962)
provides additional support for Siffre’s findings. Aschoff & Weber
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
studied participants living in a bunker. The bunker had no windows and
only artificial light, which the participants were free to turn on and off
as they pleased. Aschoff & Weber found that the participants settled
into a longer sleep/wake cycle of between 25-27 hours. These results,
along with Siffre’s findings, suggest that humans use natural light
(exogenous zeitgebers) to regulate a 24-hour circadian sleep-wake
cycle, demonstrating the importance of light for this circadian rhythm.
Individual Differences: However, it is important to note the differences between
individuals when it comes to circadian cycles. Duffy et al. (2001) found that
‘morning people’ prefer to rise and go to bed early (about 6 am and 10 pm)
whereas ‘evening people’ prefer to wake and go to bed later (about 10 am and 1
am). This demonstrates that there may be innate individual differences in circadian
rhythms, which suggests that researchers should focus on these differences during
investigations.

Additionally, it has been suggested that temperature may be more important than
light in determining circadian rhythms. Buhr et al. (2010) found that fluctuations in
temperature set the timing of cells in the body and caused tissues and organs to
become active or inactive. Buhr claimed that information about light levels is
transformed into neural messages that set the body’s temperature. Body
temperature fluctuates on a 24-hour circadian rhythm and even small changes in it
can send a powerful signal to our body clocks. This shows that circadian rhythms
are controlled and affected by several different factors, and suggests that a more
holistic approach to research might be preferable.
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2. Endogenous Pacemakers & Exogenous Zeitgebers
Biological rhythms are regulated by endogenous pacemakers, which are the body’s
internal biological clocks, and exogenous zeitgebers, which are external cues, including
light, that help to regulate the internal biological clocks.
Exam Hint: It’s important to note that endogenous pacemakers and exogenous
zeitgebers interact with one another to control and fine-tune biological rhythms and
therefore it is necessary to consider these concepts together.
Endogenous Pacemakers
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Endogenous pacemakers are internal mechanisms that govern biological rhythms, in
particular, the circadian sleep-wake cycle. Although endogenous pacemakers are
internal biological clocks, they can be altered and affected by the environment. For
example, although the circadian sleep-wave cycle will continue to function without
natural cues from light, research suggests that light is required to reset the cycle every
24 hours. (See Siffre and Aschoff & Weber, above)
PL
The most important endogenous pacemaker is the suprachiasmatic nucleus, which is
closely linked to the pineal gland, both of which are influential in maintaining the
circadian sleep/wake cycle.
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The suprachiasmatic nucleus (SCN), which lies in the hypothalamus, is the main
endogenous pacemaker (or master clock). It controls other biological rhythms, as it
links to other areas of the brain responsible for sleep and arousal. The SCN also
receives information about light levels (an exogenous zeitgeber) from the optic nerve,
which sets the circadian rhythm so that it is in synchronisation with the outside world,
e.g. day and night.
The SNC sends signals to the pineal gland, which leads to an increase in the production
of melatonin at night, helping to induce sleep. The SCN and pineal glands work
together as endogenous pacemakers; however, their activity is responsive to the
external cue of light. Put simply:
Exogenous Zeitgebers
As outlined above, exogenous zeitgebers influence biological rhythms: these can be
described as environmental events that are responsible for resetting the biological
clock of an organism. They can include social cues such as meal times and social
activities, but the most important zeitgeber is light, which is responsible for resetting
the body clock each day, keeping it on a 24-hour cycle.
The SNC contains receptors that are sensitive to light and this external cue is used to
synchronise the body’s internal organs and glands. Melanopsin, which is a protein in
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the eye, is sensitive to light and carries the signals to the SCN to set the 24-hour daily
body cycle. In addition, social cues, such as mealtimes, can also act as zeitgebers and
humans can compensate for the lack of natural light, by using social cues instead.
Evaluating Endogenous Pacemakers & Exogenous Zeitgebers
The importance of the SCN has been demonstrated in research. Morgan (1955)
bred hamsters so that they had circadian rhythms of 20 hours rather than 24. SCN
neurons from these abnormal hamsters were transplanted into the brains of
normal hamsters, which subsequently displayed the same abnormal circadian
rhythm of 20 hours, showing that the transplanted SCN had imposed its pattern
onto the hamsters. This research demonstrates the significance of the SCN and
how endogenous pacemakers are important for biological circadian rhythms.
o However, this research is flawed because of its use of hamsters. Humans
would respond very differently to manipulations of their biological rhythms,
not only because we are different biologically, but also because of the vast
differences between environmental contexts. This makes research carried
out on other animals unable to explain the role of endogenous pacemakers
in the biological processes of humans.

There is research support for the role of melanopsin. Skene and Arendt (2007)
claimed that the majority of blind people who still have some light perception have
normal circadian rhythms whereas those without any light perception show
abnormal circadian rhythms. This demonstrates the importance of exogenous
zeitgebers as a biological mechanism and their impact on biological circadian
rhythms.
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There is further research support for the role of exogenous zeitgebers. When Siffre
(see above) returned from an underground stay with no clocks or light, he believed
the date to be a month earlier than it was. This suggests that his 24-hour sleepwake cycle was increased by the lack of external cues, making him believe one day
was longer than it was. This highlights the impact of external factors on bodily
rhythms.

Despite all the research support for the role of endogenous pacemakers and
exogenous zeitgebers, the argument could still be considered biologically
reductionist. For example, the behaviourist approach would suggest that bodily
rhythms are influenced by other people and social norms, i.e. sleep occurs when it
is dark because that is the social norm and it wouldn’t be socially acceptable for a
person to conduct their daily routines during the night. The research discussed
here could be criticised for being reductionist as it only considers a singular
biological mechanism and fails to consider the other widely divergent viewpoints.
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3. Infradian Rhythms & Ultradian Rhythms
Infradian Rhythms
Another important biological rhythm is the infradian rhythm. Infradian
rhythms last longer than 24 hours and can be weekly, monthly or annually.
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A monthly infradian rhythm is the female menstrual cycle, which is
regulated by hormones that either promote ovulation or stimulate the
uterus for fertilisation. Ovulation occurs roughly halfway through the cycle
when oestrogen levels are at their highest, and usually lasts for 16-32 hours.
After the ovulatory phase, progesterone levels increase in preparation for
the possible implantation of an embryo in the uterus. It is also important to
note that although the usual menstrual cycle is around 28 days, there is
considerable variation, with some women experiencing a short cycle of 23
days and others experiencing longer cycles of up to 36 days.
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Extension: A second example of an infradian rhythm is related to the
seasons. Research has found seasonal variation in mood, where some people
become depressed in the winter, which is known as seasonal affective
disorder (SAD). SAD is an infradian rhythm that is governed by a yearly cycle.
Psychologists claim that melatonin, which is secreted by the pineal gland
during the night, is partly responsible. The lack of light during the winter
months results in a longer period of melatonin secretion, which has been
linked to the depressive symptoms.
Exam Hint: While it is logical to assume that infradian rhythms, in
particular the menstrual cycle, are governed by internal factors
(endogenous pacemakers) such as hormonal changes, research suggests
that these infradian rhythms are heavily influenced by exogenous
zeitgebers.
Evaluating Infradian Rhythms
 Research suggests that the menstrual cycle is, to some extent, governed
by exogenous zeitgebers (external factors). Reinberg (1967) examined a
woman who spent three months in a cave with only a small lamp to
provide light. Reinberg noted that her menstrual cycle shortened from
the usual 28 days to 25.7 days. This result suggests that the lack of light
(an exogenous zeitgeber) in the cave affected her menstrual cycle, and
therefore this demonstrates the effect of external factors on infradian
rhythms.
 There is further evidence to suggest that exogenous zeitgebers can affect
infradian rhythms. Russell et al. (1980) found that female menstrual
cycles became synchronised with other females through odour exposure.
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In one study, sweat samples from one group of women were rubbed
onto the upper lip of another group. Despite the fact that the two groups
were separate, their menstrual cycles synchronised. This suggests that
the synchronisation of menstrual cycles can be affected by pheromones,
which have an effect on people nearby rather than on the person
producing them. These findings indicate that external factors must be
taken into consideration when investigating infradian rhythms and that
perhaps a more holistic approach should be taken, as opposed to a
reductionist approach that considers only endogenous influences.
o Evolutionary psychologists claim that the synchronised
menstrual cycle provides an evolutionary advantage for groups
of women, as the synchronisation of pregnancies means that
childcare can be shared among multiple mothers who have
children at the same time.
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 There is research to suggest that infradian rhythms such as the menstrual
cycle are also important regulators of behaviour. Penton-Volk et al.
(1999) found that woman expressed a preference for feminised faces at
the least fertile stage of their menstrual cycle, and for a more masculine
face at their most fertile point. These findings indicate that women’s
sexual behaviour is motivated by their infradian rhythms, highlighting the
importance of studying infradian rhythms in relation to human
behaviour.
 Finally, evidence supports the role of melatonin in SAD. Terman (1988)
found that the rate of SAD is more common in Northern countries where
the winter nights are longer. For example, Terman found that SAD affects
roughly 10% of people living in New Hampshire (a northern part of the
US) and only 2% of residents in southern Florida. These results suggest
that SAD is in part affected by light (exogenous zeitgeber) that results in
increased levels of melatonin.
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Ultradian Rhythms
Ultradian rhythms last fewer than 24 hours and can be found in the pattern of
human sleep. This cycle alternates between REM (rapid eye movement) and NREM
(non-rapid movement) sleep and consists of five stages. The cycle starts at light
sleep, progressing to deep sleep and then REM sleep, where brain waves speed up
and dreaming occurs. This repeats itself about every 90 minutes throughout the
night.
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A complete sleep cycle goes through the four stages of NREM sleep before
entering REM (Stage 5) and then repeating. Research using EEG has highlighted
distinct brain waves patterns during the different stages of sleep.
1. Stages 1 and 2 are ‘light sleep’ stages. During these stages brainwave
patterns become slower and more rhythmic, starting with alpha waves
progress to theta waves.
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2. Stages 3 and 4 are ‘deep sleep’ or slow wave sleep stages, where it is
difficult to wake someone up. This stage is associated with slower delta
waves.
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3. Finally, Stage 5 is REM (or dream) sleep. Here is the body is paralysed (to
stop the person acting out their dream) and brain activity resembles that of
an awake person.
On average, the entire cycle repeats every 90 minutes and a person can
experience up to five full cycles in a night.
Exam Hint: When providing an example of an ultradian rhythm, answers should
explicitly mention that the cycle occurs more than once every 24 hours.
Furthermore, specific details in relation to the distinctive characteristics of the
different stages are required to demonstrate understanding.
Extension: Another ultradian rhythm is appetite or meal patterns in humans. Most
humans eat three meals a day and appetite rises and falls because of food
consumption.
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Evaluating Ultradian Rhythms
Individual Differences: The problem with studying sleep cycles is the
differences observed in people, which make investigating patterns difficult.
Tucker et al. (2007) found significant differences between participants in terms
of the duration of each stage, particularly stages 3 and 4 (just before REM
sleep). This demonstrates that there may be innate individual differences in
ultradian rhythms, which means that it is worth focusing on these differences
during investigations into sleep cycles.
o In addition, this study was carried out in a controlled lab setting, which
meant that the differences in the sleep patterns could not be attributed
to situational factors, but only to biological differences between
participants. While this study provide convincing support for the role of
innate biological factors and ultradian rhythms, psychologists should
examine other situational factors that may also play a role.

Additionally, the way in which such research is conducted may tell us little
about ultradian rhythms in humans. When investigating sleep patterns,
participants must be subjected to a specific level of control and be attached to
monitors that measure such rhythms. This may be invasive for the participant,
leading them to sleep in a way that does not represent their ordinary sleep
cycle. This makes investigating ultradian rhythms, such as the sleep cycle,
extremely difficult as their lack of ecological validity could lead to false
conclusions being drawn.
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
An interesting case study indicates the flexibility of ultradian rhythms. Randy
Gardener remained awake for 264 hours. While he experienced numerous
problems such as blurred vision and disorganised speech, he coped rather well
with the massive sleep loss. After this experience, Randy slept for just 15 hours
and over several nights he recovered only 25% of his lost sleep. Interestingly,
he recovered 70% of Stage 4 sleep, 50% of his REM sleep, and very little of the
other stages. These results highlight the large degree of flexibility in terms of
the different stages within the sleep cycle and the variable nature of this
ultradian rhythm.
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Possible Exam Questions
1. Short Answer Question: Outline one or more examples of circadian rhythms. (4
marks)
2. Short Answer Question: Outline one or more examples of ultradian rhythms. (4
marks)
Exam Hint: Students often lose marks on short answer questions by not focusing their
response. The most accessible example for this question is the alternation between
NREM and REM sleep. However, top mark answers need to provide details of this
alternation, including the number of episodes per night and the distinctive
characteristics of each stage. Another example could include meal patterns in humans.
Some students confuse ultradian and infradian rhythms and claim that temperature
and the sleep/wake cycle is an example of ultradian, which is incorrect.
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3. Short Answer Question: Outline one or more examples of infradian rhythms. (4
marks)
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4. Short Answer Question: Outline what research into circadian rhythms has found.
(4 marks)
5. Short Answer Question: Outline what research into ultradian/infradian rhythms
has found. (4 marks)
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6. Short Answer Question: What is meant by the terms endogenous pacemakers and
exogenous zeitgebers. (4 marks)
7. Application: John is an electrician and has just started a new job where he works
shifts. He works 4 day shifts, then has 4 days off, and then works 4 night shifts.
After working night shifts, John finds it difficult to sleep during the day and
becomes very frustrated. Using your knowledge of endogenous pacemakers and
exogenous zeitgebers, explain John’s experiences. (4 marks)
8. Essay: Outline and evaluate circadian rhythms. (16 marks)
9. Essay: Outline and evaluate infradian and/or ultradian rhythms. (16 marks)
10. Essay: Discuss research into the disruption of biological rhythms. (16 marks)
Exam Hint: You can answer this question by considering the effects of shift work on
mood, physical illness and productivity; the beneficial effects of altering shift work
patterns; and the effects of jet lag on physical health.
11. Essay: Discuss the consequences of disrupting biological rhythms. (16 marks)
Exam Hint: While this question may appear similar to the above, the focus of this
question needs to be on ‘the consequences’ of disruption and not just a descriptive
outline of the research.
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12. Essay: Outline and evaluate the effect of endogenous pacemakers and exogenous
zeitgebers on the sleep-wake cycle. (16 marks)
Extension: Disruption of Biological Rhythms
One of the more difficult sample questions is to discuss the consequences of disrupting
biological rhythms and this section will focus on a different area that examines the
disruption in the sleep-wake cycle for people who work at night (shift workers).
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People who work at night (shift work) often experience symptoms similar to jet lag.
This is because the person’s work schedule (exogenous zeitgeber) is at odds with their
circadian sleep-wave cycle, which is governed by powerful biological factors
(endogenous pacemakers). Not surprisingly, people who work shift work often feel
sleepy at work and suffer from insomnia at home.
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There are numerous consequences for people who work shifts, including:
 Sleep Deprivation: People who work at night and have to sleep during the day
often experience difficulties in sleeping. This is because their biological clocks
(endogenous pacemakers) do not adjust completely. Furthermore, the daytime is
associated with significantly more noise and other disturbances that can also affect
sleep.
o Research suggests that daytime sleep is shorter than night-time sleep. Tilley
and Wilkinson (1982) suggest that REM is particularly affected and this
reduction in sleep results in sleep deprivation, which produces lower levels
of energy and reduces alertness during the night time (awake period).

Heart Disease: There is a relationship between shift work and heart disease.
o Knutsson (1986) found that people who worked shift patterns for more
than 15 years were significantly more likely to develop heart disease. This
research highlights the negative health consequences of disrupting
biological rhythms, in particular the sleep-wake cycle. However, it is worth
noting that these findings are purely correlational and while the findings
might indicate a link between the disruption of biological rhythms and
heart disease, other factors may also play a significant role. For example, it
may be that jobs that require night time working are inherently more
stressful and it is the stress that is the major factor and not the shift work.

Social Consequences: Another issue that people who work shift patterns
experience is social disruption. People who work hours that are at odds with the
hours worked by their family and friends find it difficult to spend quality time with
significant others.

Practical Applications: While the research above highlights a series of negative
consequences associated with disrupting biological rhythms, Czeisler et al. (1982)
used research on shift work to improve the health and performance of shift
workers. They found that by using a phase system to make shift changes slower,
workers reported increased satisfaction and increase productivity. This suggests
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that the negative impact of disrupting biological rhythms can be overcome by
slowly introduce people to night work.
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