PS4529/30
Applications
of Cognitive
Neuroscience
Lectures 7/8 – where is my mind?
Lectures 9/10 – what is episodic Memory?
Lecture 11/12 – Cognitive neuroscience in the
courtroom: the special case of episodic memory.
Key concepts that underpin Cognitive
Neuroscience
Electrophysiological
Haemodynamic
Psychophysiology
• Aim is to develop mind reading technologies
• We are most interested in the PPY of
Perception and Cognition. In other words,
Cognitive Neuroscience
• Can we tell what a person is thinking or
experiencing just by looking at their brain
activity?
Phrenology Was Odd…
• There is no known mechanism that would sculpt
the contours of the skull according to underlying
brain shape
• i.e. there is no correlation between contours
of the skull and the underlying size or shape
of the brain
• Their psychological ‘model’ was based on
common sense constructs of personality
• I.e. Looking in the wrong place for the wrong
thing!
But not entirely wrong…
• The idea of functional localisation has survived,
but in a different form
• Localisation does not respect character traits,
like honesty, peevishness
• Localisation may respect, for example,
sensory modality, ‘cognitive systems’ (e.g.
LTM), along with other psychological
mechanisms yet to be elucidated
Acceptable ‘modern’ principles of
functional neuroanatomy
• Functional Segregation
• Discrete cognitive functions are localised to
specific parts/circuits of the brain (complex
tasks are ‘divided and conquered’)
• Functional Integration
• Coordinated interactions between functionally
specialised areas (e.g. during retrieval from
episodic memory, reading, perceptual binding
etc)
Summary so far
• We want to read a person’s mind from the
activity of their brain. E.G. are they lying?
• Their mind is composed of lots of interacting
cognitive processes
• Each distinct process is carried out by networks
of brain regions, each region is probably
performing specific functions, but they all work
together
• So we need a device or a technique that can
detect changes in brain activity specific to any
cognitive process
How to proceed?
• In an experiment we engage different functions
in different conditions. For every condition we
• Detect rapid changes in neuronal activity (requires a
temporal resolution of milliseconds, 1/100ths of a
second)
• Locate activity within brain structures that are engaged
(may require an anatomical (spatial) resolution of
millimeters or better)
• Currently no such technique exists. Instead we
rely on converging data from many techniques
Electrophysiological Techniques
• EEG
• non-invasive
recordings from an
array of scalp
electrodes
EEG Signal Averaging
Averaging EEG produces ERPs
• Portions of the EEG
time-locked to an
event are averaged
together, extracting
the neural
signature for the
‘event’.
SHOE
+
10uV
-
AVERAGE
0
1
TIME (sec)
2
What do ERP waveforms tell us?
+
5uV
-
0
1
TIME (seconds)
2
INFORMATION
ABOUT THE
NEURAL BASIS
OF PROCESSING
IS PROVIDED BY
THE DIFFERENCE
IN ACTIVITY
Functional Inferences Based Upon
Electrophysiology
• Timing
• Upper limit on time it takes
for neural processing to
differ
• Time course of a process
(onset, duration, offset)
• Level at which a process is
engaged
• Engagement of multiple
processes at different times or
in different conditions
Early Topography
Late Topography
The Brain’s Plumbing
Haemodynamic Techniques
• Oxygen and glucose are supplied by the
blood as ‘fuel’ (energy) for the brain
• The brain does not store fuel, so
• Blood supply changes as needs arise
• Changes are regionally specific - following
the local dynamics of neuronal activity
within a region
• Haemodynamic techniques localise brain
activity by detecting these regional changes
in cerebral blood supply
Positron Emission Tomography
(PET)
• Samples the entire brain
volume homogeneously
• Has an effective anatomical
resolution of about 10mm or
so in group studies
• An ‘indirect’ measure of
neuronal activity
• Due to radiation dose, only a
limited number of scans can
be taken from each subject
Magnetic Resonance Imaging
(MRI)
• Put head into a strong magnetic field
• Water protons align themselves with
respect to the field
• alignment is then perturbed by
radio-frequency pulses
• non-invasive and fast (few seconds)
• protons ‘relax’ back into alignment,
giving off a signal
• relaxation signals can reveal
• tissue type
• physiological state (e.g. blood
oxygenation)
• 3D position in the magnetic field
Our starting point …
• Electrophysiological and Haemodynamic
techniques
• Have different temporal and spatial resolutions
• Measure different physiological signals
• Constrain experimental design and functional
inferences in different ways
• May provide complementary information when
functional maps from each technique can be
formally co-registered
ERP
PET