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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
• 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.
How Neurons Communicate
• Measuring action potentials
– Microelectrodes pick up electrical signal
– Placed near axon
– Active for ~1 second
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
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
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Localization of Function
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
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
• Severe Broca’s Aphasia
• Expressive Aphasia
• Werneckie’s Aphasia
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
Putting it all Together: 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
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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
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