Cognitive Neuroscience
An introduction
Emanuele De Luca | Department of Psychology
Overview
Part 1
A.
B.
Background and introduction
Neuroimaging techniques
Part 2
Mirror neurons
Part 1(A)
Background and introduction
Mind and Brain: An Empirical
Example

Wilder Penfield (btw 1928 and 1947)

Direct electrical stimulation of cortex

Produces "mental" sensations of thinking,
perceiving, etc. rather than a sense of the brain
being stimulated

"a star came down and towards my nose", "those
fingers and my thumb gave a jump", "I heard the
music again; it is like the radio"
Mind and Brain: Cognitive
Neuroscience Approach

Cognitive neuroscience aims to provide
a brain-based account of cognitive
processes (thinking, perceiving,
remembering etc.)

Made possible by technological advances in
studying the brain that are safer and less
crude than, say, Penfield’s method
Historical Foundations

Do mental experiences arise in the heart (e.g. Aristotle
ca. 384 BC) or brain (e.g. Hippocrates ca. 460 BC)?

How can a physical substance (brain/body) give rise to
mental experiences? = MIND–BODY PROBLEM
- Dualism – mind and body are separate substances (e.g.
Descartes)
- Dual-aspect theory – mind and body are two levels of
explanation of the same thing (e.g. like wave-particle duality)
- Reductionism – mind eventually explained solely in terms of
physical/biological theory

These issues still relevant to modern cognitive
neuroscience
Historical Foundations

Early anatomists
believed ventricles
important

Cortex was often
schematically drawn
(top) or misrepresented
like intestines (bottom
left) until 18th century

Gall and Spurzheim
(1810, bottom right)
provide an accurate
depiction
Phrenology (Franz Joseph Gall,1796)

Different parts of cortex serve
different functions

Differences in personality
traits manifest in differences
in cortical size and bumps on
skull

Crude division of
psychological traits (e.g. "love
of animals") and not
grounded in science
Mark Sykes/Science Photo Library
Functional Specialization without
Phrenology

Although phrenology is discredited, the notion that
different regions of the brain serve different functions
has stood the test of time

Termed FUNCTIONAL SPECIALIZATION

Modern cognitive neuroscience uses empirical methods
to ascertain different functions

It does not assume that each region has one function or
each function has a discrete location (unlike
phrenology), but does assume some degree of
specialization of neurons in particular regions
Functional Specialization: Broca’s
Observations (1824-1880)
Copyright 2002, with permission from
Elsevier

Patient with left
frontal lesion (Tan)
who could not speak
but had otherwise
good cognitive
abilities

Suggested a
specialized language
faculty in the brain
Functional Specialization: After
Broca

Wernicke (1848-1905) later observed a patient with poor speech
comprehension, but good production

Suggests at least two language faculties in the brain (comprehension
vs production) that can be independently affected by brain damage

Note that the faculties were inferred from empirical observation
(unlike phrenological faculties)

This inference can be made without necessarily knowing where in
the brain they are located

This approach later became known as COGNITIVE
NEUROPSYCHOLOGY
The New Phrenology?

Uttal has argued that
functional imaging is the new
phrenology

Stories in the popular press
do little to allay these
concerns

Important to consider
computational processes
rather than simple
localization and also to
consider how brain systems
interact. This may avoid a
new phrenology
The Return of the Brain: Cognitive
Neuroscience

1970s: structural imaging methods (CT, MRI) enable
precise images of the brain (and brain lesions)

1980s: PET adapted to models of cognition developed
by psychologists

1985: TMS is first used (a non-invasive, safer
equivalent of Penfield’s earlier studies)

1990: Level of oxygen in blood used as a measure of
cognitive function (the principle behind fMRI)
The Methods of Cognitive
Neuroscience

Temporal
resolution

Spatial
resolution

Invasiveness
Part 1(B)
Neuroimaging techniques
Brain Reading?
To what extent can we tell what someone is
thinking by monitoring momentary changes
in their brain?
 What do techniques such as fMRI actually
measure?
 What are the limitations and usefulness of
the various methods?

Video
http://www.youtube.com/watch?v=3eZTAA
It3QU
The Active Brain: overview

Cognitive activity is associated with increased
activity of neurons
 Neurons performing similar functions tend to
cluster together (functional specialization)
 Neural activity generates electrical signals –
measured by electrophysiological techniques
 Neural activity leads to oxygen consumption
and this leads to localized changes in blood
flow (a haemodynamic response) – measured
by functional imaging (PET, fMRI)
Revision of Neural Electrical
Activity

Axons propagate action potentials (sudden
depolarization of membrane)
 The electrical input from lots of different neurons
is summed together. If it exceeds a threshold
then the receiving neuron will also generate an
action potential.
Action Potentials summed
Action potential
Two Main Electrophysiological
Techniques
(1) Single-cell recordings
Electrode/s placed in or near a neuron
(invasive)
 Measure number of action potentials per
second

(2) Event-related potentials (ERP)
Electrode/s placed on the skull
 Measures summed electrical potentials from
millions of neurons (sensitive to dendritic
currents, pyramidal neurons)

Single-Cell Recordings



Enable researchers to understand how individual neurons code
information
How specific is the response of neurons? For example, could one find
a neuron that responded to just one face (a "grandmother cell")?
Neurons may respond to faces more than objects, and to some faces
more than others
Have you a granma neuron?
Single-Cell Recordings
© University of Taiwan, Faculty of Psychology
Single-Cell Recordings


Neurons may respond to conceptual properties of a
stimulus too
For example, this neuron responds when gaze is
oriented downwards (even though the physical pose is
very different)
Event-Related Potentials (ERPs)

Based on EEG (electroencephalography)
recordings
 EEG signal is averaged over many events (to
reduce effects of random neural firing) and
synchronized to some aspect of the event (e.g.
onset of stimulus, pressing a button)
 Electrodes record a series of positive and
negative peaks
 Timing and amplitude of the peaks is related to
different aspects of the stimulus and task (e.g.
consider face recognition)
Event-Related Potentials (ERPs)
Pyramidal neurons of the cortex
N170 component for faces
Advantages and Disadvantages of
ERP

ERP signal is directly related to neural activity
and this electrical activity is conducted
instantaneously to the scalp
 Therefore, ERP has an excellent temporal
resolution
 The ERP signal is derived from different sources
in the brain and it is not possible to infer exactly
where these sources are from the scalp
 Therefore, ERP has a poor spatial resolution
Functional Imaging





Neural activity consumes oxygen as well as
generating electrical signals
In order to compensate for increased oxygen
consumption, more blood is pumped into the
active region
PET measures the blood flow in a region,
whereas fMRI measures the blood
oxygenation
The time taken for this response is slow
(several seconds) and so functional imaging
has a poor temporal resolution, but a good
spatial resolution
This is the complementary profile to EEG
Positron Emission Tomography
(PET)

Measures local
blood flow
 Radioactive tracer
injected into blood
stream
 Tracer takes up to
30 seconds to peak
Catherine Pouedras/Science Photo
Library
Functional Magnetic Resonance
Imaging (fMRI)

Does not use radioactivity, but directly measures
the concentration of deoxyhaemoglobin in the
blood
 This is called the BOLD response (Blood
Oxygen Level Dependent contrast)
 The change in BOLD response over time is
called the haemodynamic response function and
it has a number of distinct phases (not to be
confused with the ERP waveform, which is
completely unrelated)
 The Haemodynamic Response Function peaks
in 6–8 seconds and so this is the temporal
resolution of fMRI
Functional Magnetic Resonance
Imaging (fMRI)

Haemodynamic response function (change in
BOLD signal over time)
Cortex: laminated gray matter covering of brain
MRI (T1weighted):
Gray matter = cells
White matter = axons
Face processing areas in the human brain
What does it mean to say a brain
region is "active"?





The brain has a constant supply of blood and oxygen; if
it didn’t, it would die
This means we cannot literally stick someone in a
scanner and read their thoughts (because the whole
brain would look active)
In order to infer functional specialization, one needs to
compare RELATIVE differences in brain activity between
two or more conditions
A region is "active" if it shows a greater response in one
condition relative to another
If the experimenter chooses inappropriate conditions the
regions of activity will be meaningless (junk in, junk out)
– functional imaging isn’t straightforward
Lie Detection
Lie Detection





Traditional polygraph measures bodily response
(e.g. sweating, heart rate), but what if someone
doesn’t feel guilty?
Brain is the organ that creates the lie
Anterior cingulate cortex is active when asked to
generate false answers to questions relative to
truthful ones (e.g. “where was your last
vacation?”)
This region believed to be involved in monitoring
conflicts between responses
BUT, not necessarily active if lie is memorized in
advance
Is Brain Reading Possible?

Most experiments manipulate cognitive
processing and measure changes in brain
response
 Can the reverse be done, i.e. can the brain
response be used to infer what people are
thinking?
 Brain response can be used to predict which
object is seen or imagined from a limited set
(e.g. face vs house vs cats vs shoes) with ~90%
accuracy
 However, can only be done if experimenter pretests the participants on these items (to know
where to look in that particular person)
Limits on Brain Reading

Each brain is subtly different anatomically
 May be able to measure general contents of
thought (e.g. a face) rather than specific
contents (e.g. Tony Blair’s face)
 Not easy to distinguish between conscious
and unconscious cognition just from looking at
the brain
TMS: Reverse Engineering



Infer the function of a region (or cognitive mechanism)
by removing it and measuring the effect on the rest of
the system
For example, if damage to a region disrupts reading,
but not speaking or seeing, then one might conclude
that the region is specialized for some aspect of
reading
Disruption of brain function comes about through
natural damage (strokes, etc.), elicited damage (e.g.
animal models), or harmless temporary changes
induced electro-magnetically (TMS)
Transcranial Magnetic Stimulation
(TMS)




Coil contains a wire carrying
an electric current
A rapid change in the current
creates a magnetic field
The magnetic field induces a
current in the nearby neurons
(causing them to "fire", i.e.
generate action potentials)
This disrupts the cognitive
function that they may be
doing at that point in time (
virtual lesion)
Simon Fraser/Science Photo Library
Part 2
Mirror neurons
Video
http://www.youtube.com/watch?v=BOd3N2
0XNC4&feature=related
Definition:
Mirror neurons are a class of neurons in
the parietal lobe.
 Discovered monkeys in 1992 (Rizzolatti
Lab) and studied ever since then.
 They fire both when the animal performs
an action (grasps an object) and when
sees another individual make a similar
action (monkey or human).

Research Paradigm
Microscopic electrodes inserted into
single neurons.
 Monkey hooked to machine which
records
 Discovery of the function of these
neurons happened by accidental
(anecdote of the nut).

Single-Cell Recording
© University of Taiwan, Faculty of Psychology
Finding mirror neurons
Pre-motor and posterior
parietal cortex neuron
responses in the monkey
a) Observed action
b) Executed action
Only when movement has
a purpose (is an action)
neurons fire
Specific to action type
(pick up or move peanut)
Mirror Neuron facts

For these neurons to fire the monkey has to
see an object-directed action (object alone or
hand movement alone is not enough).
 The mere observation of an object not acted
upon does not evoke a response either.
 Reward not relevant to firing.
 Mirror neurons can be driven not only by
action execution and observation, but also by
the sound produced by the same action
Mechanism of action understanding
Each time monkey sees action by
another individual, neurons that are
activated when the same action is
executed by himself are firing.
 Thus the monkey has knowledge of the
other’s action from his own activity.

Human Mirror Neurons
The mirror neuron system for actions in
humans cannot be directly studied.
 fMRI paradigms
 Rizzolatti (in 2005) found that when
people listened to sentences describing
actions, the same mirror neurons fired as
would have fired had they performed the
actions or witnessed them being
performed.

Human Mirror Neuron
System
Empathy - emotions
Mirror neuron network in man involves
and activates Amygdala (emotions)
 We do not accomplish understanding of
other’s feelings by analogy or thinking
processes.
 Rather, the other’s emotion is
experienced by ourselves and therefore
directly understood. It is a shared body
state.

Evolution of language

1)
2)
Once you have two abilities in place;
the ability to read someone's intentions
(through your own)
the ability to mime their vocalizations
then you have set in motion the
evolution of language. (You need no
longer speak of a unique language
organ and the evolution of language
doesn't seem quite so mysterious any
more).
Social Skills

Anytime you watch someone else doing
something (or even starting to do
something), the corresponding mirror
neuron fires in your brain, thereby
allowing you to "read" and understand
another's intentions, and thus to develop
a sophisticated "theory of other minds."
Mirror neurons in Autism

Mirror neurons that fired in nonautistic people
watching someone else make meaningless
finger movements didn’t fire in autistic
children.
 Both autistic and nonautistic adolescents
watched pictures of people with distinctive
facial expressions. Both subjects could imitate
the expressions and say what emotions they
expressed. But while the nonautistic teens
showed robust activity in mirror neurons
corresponding to the emotions expressed, the
autistic teens showed no such activity.

They understood the expressions cognitively but felt
no empathy.
Conclusions: Ramachandran

"I predict that mirror neurons will do for
psychology what DNA did for biology,"
 "They will provide a unifying framework and
help explain a host of mental abilities that have
hitherto remained mysterious and
inaccessible."
 Mirror neurons primed the human brain for the
great cultural leap forward.
 Once we had the ability to imitate, and learn
through imitation, transmission of culture is
possible.
THANKS FOR LISTENING
e.deluca@psy.gla.ac.uk