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Chapter 2
Cognitive Neuroscience
Some Questions to Consider
• What is cognitive neuroscience, and why is it
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necessary?
How is information transmitted from one
place to another in the nervous system?
How are things in the environment, such as
faces and trees, represented in the brain?
Is it possible to read a person’s mind by
measuring the activity of the person’s brain?
Building Blocks of the Nervous System
• Neurons: cells specialized to receive and
transmit information in the nervous system
• Each neuron has a cell body, an axon, and
dendrites
Building Blocks of the Nervous System
• Cell body: contains mechanisms to keep cell
alive
• Axon: tube filled with fluid that transmits
electrical signal to other neurons
Building Blocks of the Nervous System
• Dendrites: multiple branches reaching from
the cell body, which receives information from
other neurons
– Sensory receptors: specialized to respond
to information received from the senses
Caption: A portion of the brain that has been treated with Golgi stains
shows the shapes of a few neurons. The arrow points to a neuron’s
cell body. The thin lines are dendrites or axons.
Caption: Basic components of the neuron. The one on the left
contains a receptor, which is specialized to receive information from
the environment (in this case, pressure that would occur from being
touched on the skin). This neuron synapses on the neuron on the
right, which has a cell body instead of a receptor.
How Neurons Communicate
• Action potential
– Neuron receives signal from environment
– Information travels down the axon of that
neuron to the dendrites of another neuron
How Neurons Communicate
• Measuring action potentials
– Microelectrodes pick up electrical signal
– Placed near axon
– Active for ~1 second
Caption: (a) Action potentials are recorded from neurons with tiny microelectrodes that are
positioned inside or right next to the neuron’s axon. These potentials are displayed on the
screen of an oscilloscope and are also sent to a computer for analysis. (b) An action
potential recorded by a microelectrode looks like this. The inside of the axon becomes
more positive, then goes back to the original level, all within 1 millisecond (1/1,000
second). (c) A number of action potentials displayed on an expanded time scale, so a
single action potential appears as a “spike”.
How Neurons Communicate
• Measuring action potentials
– The size is not measured; size remains
consistent
– The rate of firing is measured
• Low intensities: slow firing
• High intensities: fast firing
Caption: Records showing action potentials in a neuron that responds
to light entering the eye. (a) Presenting light causes an increase in
firing; (b) increasing the light intensity increases the rate of firing
further; and (c) even more light results in a high rate of firing.
How Neurons Communicate
• Synapse: space between axon of one neuron
and dendrite of another
• When the action potential reaches the end of
the axon, synaptic vesicles open and release
chemical neurotransmitters
• Neurotransmitters cross the synapse and
bind with the receiving dendrites
How Neurons Communicate
• Neurotransmitters: chemicals that affect the
electrical signal of the receiving neuron
– Excitatory:
increases chance neuron will fire
– Inhibitory:
decreases chance neuron will fire
How Neurons Process Information
• Not all signals received lead to action
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potential
The cell membrane processes the number of
impulses received
An action potential results only if the
threshold level is reached
– Interaction of excitation and inhibition
Localization of Function
• Specific functions are served by specific
areas of the brain
• Cognitive functioning breaks down in specific
ways when areas of the brain are damaged
• Cerebral cortex (3-mm thick layer that covers
the brain) contains mechanisms responsible
for most of our cognitive functions
Lobes of the Cerebral Cortex
• Frontal
– Reasoning and planning
– Language, thought, memory, motor functioning
• Parietal
– Touch, temperature, pain, and pressure
• Temporal
– Auditory and perceptual processing
– Language, hearing, memory, perceiving forms
• Occipital
– Visual processing
Localization of Function: Limbic System
• Hippocampus: forming memories
• Amygdala: emotions and emotional memories
• Thalamus: processing information from
vision, hearing, and touch senses
Localization of Function: Perception
• Primary receiving areas for the senses
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– Occipital lobe: vision
– Parietal lobe: touch, temperature, pain
– Temporal lobe: hearing, taste, smell
Coordination of information received from all senses
– Frontal lobe
Localization of Function: Perception
• Fusiform face area (FFA) responds
specifically to faces
– Temporal lobe
– Damage to this area causes prosopagnosia (inability to
recognize faces)
• Parahippocampal place area (PPA) responds
specifically to places (indoor/outdoor scenes)
– Temporal lobe
• Extrastriate body area (EBA) responds
specifically to pictures of bodies and parts of
bodies
Caption: (a) The parahippocampal place area is activated by places (top
row) but not by other stimuli (bottom row). (b) The extrastriate body
area is activated by bodies (top), but not by other stimuli (bottom).
Localization of Function: Language
• Language production is impaired by damage
to Broca’s area
– Frontal lobe
• Language comprehension is impaired by
damage to Wernicke’s area
– Temporal lobe
Caption: Broca’s and Wernicke’s areas were identified in early
research as being specialized for language production and
comprehension.
Distributed Processing in the Brain
• In addition to localization of function, specific
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functions are processed by many different
areas of the brain
Many different areas may contribute to a
function
Caption: As this person watches the red ball roll by, different
properties of the ball activate different areas of his cortex. These
areas are in separate locations, although there is
communication between them.
Method: Brain Imaging
• Positron Emission Tomography (PET)
– Blood flow increases in areas of the brain
activated by a cognitive task
– Radioactive tracer is injected into person’s
bloodstream
– Measures signal from tracer at each
location of the brain
– Higher signals indicate higher levels of
brain activity
Caption: (a) Person in a brain scanner. (b) In this cross section of
the brain, areas of the brain that are activated are indicated by
the colors. Increases in activation are indicated by red and
yellow, decreases by blue and green
Method: Brain Imaging
• Subtraction technique measures brain activity
before and during stimulation presentation
• Difference between activation determines
what areas of the brain are active during
manipulation
Caption: The subtraction technique used to interpret the results of
brain imaging experiments.
Method: Brain Imaging
• Functional Magnetic Resonance Imaging
(fMRI)
– Subtraction technique
– Measures blood flow through magnetic
properties of blood
– Advantage: no radioactive tracer needed
Method: Event-Related Potential (ERP)
• Neuron “firing” is an electrical event
• Measure electrical activity on the scalp and
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make inferences about underlying brain
activity
Averaged over a large number of trials to
calculate ERPs
Advantage: continuous and rapid
measurements
Disadvantage: does not give precise location
Caption: (a) Person wearing electrodes for recording the eventrelated potential (ERP). (b) An ERP to the phrase “The cats
won’t eat.”
Representation in the Brain
• Feature detectors: neurons that respond best
to a specific stimulus
• Hubel & Wiesel (1965)
– Simple cells: neurons that respond best to
bars of light of a particular orientation
– Complex cells: neurons that respond best
to an oriented bar of light with a specific
length
Caption: Three types of stimuli that Hubel and Wiesel (1959, 1965)
found caused neurons in the cat cortex to respond. Neurons
responded to bars with a specific orientation, to bars with a specific
orientation moving in a particular direction, and bars of a particular
length moving in a particular direction. Neurons that responded to
these specific types of stimuli were called feature detectors.
Representation in the Brain
• Specificity coding: representation of a
specific stimulus by firing of specifically tuned
neurons specialized to just respond to a
specific stimulus
• Distributed coding: representation by a
pattern of firing across a number of neurons
Caption: How faces could be coded by
specificity coding. Each faces
causes one specialized neuron to
respond.
Caption: How faces could be coded by distributed
coding. Each face causes all the neurons to fire,
but the pattern of firing is different for each face.
One advantage of this method of coding is that
many faces could be represented by the firing of
the three neurons.