CHAPTER 15
Sleep and
Consciousness
The Neural Bases of Consciousness
Sleep issues and disorders
• Insomnia
– inability to sleep or to obtain adequate quality sleep
– Must occur to the extent that the person feels inadequately rested.
• Insomnia can be brought on by a number of factors,
–
–
–
–
–
Stress.
Health issues
Lack of physical activity
Over-medicaton or medication interactions
Occurs frequently in people with psychological problems, especially affective
disorders.
• May tie in with weight gain and obesity: people with insomnia show
– Waking release of hypocretin or orexin
– Lower levels of leptin and higher ghrelin levels
– Orexigenic or appetite enhancing effect
insomnia
• Many manifestations:
– Delayed sleep onset
– Nighttime waking
– Early waking
• Disruption of circadian rhythm often is cause
– Normally: body temp decreases as fall asleep
– If body temp still high at bedtime, takes longer or is more
difficult to fall asleep
– If rises too early- wake up early
Insomnia disorders
• Two mutations in circadian clock genes identified with
insomnia:
– Advanced sleep phase syndrome: early onset of sleep,
early waking
• Chronotype: internal clock synchronized to 24-hour day, but
depends on environment as well
• Are you a lark or an owl?
– Delayed sleep syndrome:
• Obviously, delayed getting to sleep
• Often not going to bed until wee hours of morning
• Treatment: stay up three hours later each day, until
completely reset clock!
Narcolepsy
• Individuals fall asleep suddenly during the daytime : go directly into REM
sleep.
• Cataplexy
– sudden experience of one component of REM sleep – atonia –
– falls to the floor paralyzed but fully awake.
• Not that sleep more, but “boundaries” between sleep and wakefulness are
disrupted- have sudden shifts
• Why? Mutated HLA-DQ6 gene that is responsible for hypocretin receptor
function
– Have low or undetectable levels of hypocretin, due to loss of hypocretin secreting
neurons in hypothalamus
– Also an HLA-DR15 gene mutation
• Treatment: stimulants; but targeting hypocretin would work better!
Sleep walking
• Some sleep disorders, such as sleep walking, related to specific
sleep stages (particularly stage 3).
– E.g., Bedwetting, night terrors, and sleep walking occur
during slow wave sleep.
– Although sleepwalking most frequent in childhood, about
3-8% of adults sleepwalk.
• Sleepwalking
– at least partially genetic
– Can be triggered by stress, alcohol, and sleep deprivation
REM SLEEP DISORDER
• REM sleep behavior disorder
– Individuals uncharacteristically physically active during REM sleep,
– Often injure themselves or their bed partners.
– Often associated with a neurological disorder, such as Parkinson’s
disease or a brain stem tumor.
• Why? Lewy bodies found in up to 2/3 patient’s brains
– abnormal aggregates of protein that develop inside nerve cells
– Inhibition of magnocelluar nucleus that normally produces atonia
during sleep
– Suggest that Parkinsons, brain tumors, and related disorders
preceded by development of Lewy bodies in medulla
• Sleep disturbances may be “soft” sign of these disorders
– As disease progresses, Lewy bodies progress up into higher brain
areas
Consciousness
Is this just being awake?
Is this being aware?
Does this involve thinking?
The Neural Bases
of Consciousness
• Consciousness
– refers to a state: A person is conscious or unconscious.
– The term also used to indicate sense of conscious experience, or
awareness of something.
– Consciousness involves short-term memory,
• Fully conscious humans have a sense of self,
– requires long-term memory.
• Consciousness varies in level
– coma and deep anesthesia on one extreme
– alert wakefulness on the other, and sleep in between.
Glasgow Coma Scale
Eyes
1
Does not
open eyes
Verbal
Makes no
sounds
Motor
Makes no
movements
2
Opens eyes in
response to
painful stimuli
Incomprehensible
sounds
Extension to
painful stimuli
(decerebrate
response)
Generally, brain injury is classified as:



Severe, with GCS ≤ 8
Moderate, GCS 9 - 12
Minor, GCS ≥ 13
3
Opens eyes
in response
to voice
Utters
inappropriate
words
Abnormal
flexion to
painful
stimuli
(decorticate
response)
4
5
Opens eyes
N/A
spontaneously
6
N/a
Confused,
disoriented
N/A
Flexion /
Withdrawal to
painful stimuli
Oriented,
converses
normally
Localizes
painful
stimuli
Obeys
commands
The Neural Bases
of Consciousness
• Three critical components of consciousness
– Awareness
– Attention
– Sense of self.
• Altered states of consciousness include
– hypnosis
– trances
– meditative states
awareness
• Awareness:
– Abstract concept
– Difficult to define, more difficult to study.
– Researchers focused on awareness of something.
• Prefrontal cortex appears to be key player in producing
awareness.
– May also involve hippocampus
– Hippocampus critical for declarative learning
– Declarative learning, by definition, involves awareness.
• Also Parietal lobes:
– ability to locate those objects in space which are necessary for
combining features of an object into a conscious whole.
Binding problem
• Issue of how the brain combines information from different
areas into a unitary whole: how integrate all the incoming
information
• Brain must bind information from area to another
• Numerous studies suggest: synchronization of activity across
brain areas binds various elements of perception into a
coherent cognitive experience.
– Forming neural networks
– Networks must be linked to other networks, forming larger
networks
– Quickly goes beyond our computational ability to work with this.
Experimental evidence
for binding
• Light paired several times with
shock to the middle finger: CSL 
USshock
• Light alone produces
synchronized firing between
visual cortex and
somatosensory cortex where
fingers represented.
• Synchrony occurs in right
hemisphere when shock
applied to left hand
• Synchrony occurs in left
hemisphere when shock
applied to right hand
attention
• Attention: brain’s means of allocating limited resources by focusing
on some neural inputs to the exclusion of others.
– Is a physiological process
– changes in attention accompanied by changes in neural activity.
• When an observer attends to an object:
– firing synchronizes between brain areas involved
– E.g., prefrontal with parietal neurons or parietal neurons with visual areas,
depending on the task.
• When attention shifts,
– E.g., during binocular rivalry
– activity shifts from one group of neurons in the visual cortex to another,
– Shifts even though stimulus inputs do not change.
Sense of self
• Critical aspect of consciousness
• The sense of self includes identity: what we refer to as “I”
– sense of agency: attribution of an action or effect to ourselves.
• Research suggests that damage to the anterior cingulate cortex
results in diminished self awareness
• Damage to right frontal-temporal cortex may produce sense of
detachment from the self.
– Farrer and Frith et al.
– sense of agency mediated by anterior insula and inferior parietal
area.
Intriguing evidence:
• Patients like HM
– Deprived of short-term memory
– But have most of long term memories of past intact,
– Typically have a strong sense of self.
• Korsakoff’s and Alzheimer’s patients
– Extensive loss of current memories, then past memories,
– Greater impairment of their sense of self.
– Indicates that loss of LTM means loss of who you are
– Interesting: occurs in reverse order
• Forget adult self and “re-enter” childhood
• Eventually, lose all of oneself
• Like randomly tearing pages from a book until all you have left
is the cover
Why sense of self
important?
• Body image contributes to a sense of self
– We have identification with our body and with its parts
– Identify actions that are “ours” versus “not ours”
– Able to identify our thoughts/actions from those of others
.
• Without long-term memory: doubtful there can be a self
– If there is memory, there is no past there
– If there is no past, there is no sense of who the person is
• A sense of self requires distinction between our self and other
selves
– Cannot understand other selves unless understand our
self.
– Mirror neurons appear critical to developing the ability to
attribute mental states to others (theory of mind).
Mirror neurons
• Neurons that fire both when one acts and when one observes
the same action performed by another
– The neuron "mirrors" the behavior of the other, as though the
observer were itself acting.
– Identified mirror neurons in primates. Dogs, birds and several
other species
• In humans, brain activity consistent with mirror neurons found
in
•
•
•
•
Premotor cortex,
Supplementary motor area,
Primary somatosensory cortex
Inferior parietal cortex
Why mirror neurons?
Several theories
• System provides physiological mechanism for perception-action
coupling
• Important for understanding the actions of others
• Also for learning new skills by imitation.
• Mirror systems may simulate observed actions, and thus
contribute to theory of mind skills
– Mirror neurons critical for language abilities.
– Help us understand actions and intentions of others
– The neural basis of the human capacity for emotions such as
empathy
• Problems with or absence of the a mirror neuron system may
underlie cognitive disorders, particularly autism and Williams
syndrome
Sense of self =
Integration of both hemispheres
• Hemispherectomy:
– surgical procedure that separates two cerebral hemispheres
– cut the corpus callosum.
– used to prevent severe epileptic seizures from crossing
the midline and engulfing the other side of the brain.
• Individuals with “split brain” show interesting
differences: raise important questions about
consciousness and the self.
Split brain patients and
“self”
• Split-brain outcomes:
– language-dominant hemisphere is conscious, while other hemisphere
is non-conscious automaton.
– But: each hemisphere capable of consciousness,
– Thus severing the corpus callosum divides consciousness into two
“selves”.
• Gazzaniga : Left hemisphere contains module that serves as
“brain interpreter.”
– integrates all cognitive processes going on simultaneously in other
modules of the brain
– If not have both hemispheres intact, brain interpreter cannot function
normally.
Dissociative identity
disorder
• Dissociative identity disorder
– Formerly known as multiple personality
– Disorder of the self
– Involves shifts in consciousness and behavior that appear to be distinct
personalities or selves.
– Causes of this disorder are not understood,
• Appears to be related to abuse
• 90 to 95% of patients report childhood physical and/or sexual abuse.
• individual creates alternate personalities (“alters”) as a
defense against persistent emotional stress.
– The alters provide escape
– Also offers opportunity to engage in prohibited forms of behavior.
– Suggests that under stress brain can isolate “memories” to protect the
major “self”
So what is consciousness? ?
• Most neurobiological theories of consciousness assume that
consciousness requires widely distributed neuronal network.
• According to some theorists
– consciousness occurs when functioning of widespread networks
becomes coordinated,
– Enables them to share and integrate information.
• Distribution of consciousness
– means that there is no center of consciousness,
– some researchers believe must be an executive function
• Brain integrator important
– area that coordinates or orchestrates activity of all the other structures.
Do animals show a sense of self?
• Frans deWall: ethologist who studies moral behavior
• Several studies with monkeys: do they notice and can they
compare what they get versus what others get
• Let’s take a look:
• http://www.wimp.com/moralbehavior/
Take home message
• Brain activity occurs on molecular/cellular level
– Quite complicated
– Huge amount of neurons firing at any time
• Individual cells must form networks
– Networks must work together
– Must be stable yet fluid
– Forms basis of “memories” throughout the brain
• No “centers” in brain
– Redundancy, redundancy, redundancy
– Duplication of centers; multiple mechanisms control similar behaviors
– Allows neuroprotection
Take home message
• Only when brain networks “work together” in elaborate,
coordinated and consistent way do we become a “person”
– Damage alters who we are, what we are
– But who we are is evolving and changing as our brain changes
• If we don’t use a process/function, there is a danger we
could lose it!
• We only have one brain: use it wisely, protect it, and
respect it!