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Chapter 13
Learning and Memory:
Basic Mechanisms
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Copyright © 2004 Allyn and Bacon
The Nature of Learning
 Learning:
• The process by which experiences change our
nervous system and hence our behaviors.
 Perceptual learning:
• Learning to recognize a particular stimulus.
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The Nature of Learning
 Classical conditioning:
• A learning procedure; when a stimulus that
initially produces no particular response is
followed several times by an unconditioned
stimulus that produces a defensive or appetitive
response.
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The Nature of Learning
 Hebb rule:
• The hypothesis proposed by Donald Hebb that
the cellular basis of learning involves
strengthening of a synapse that is repeatedly
active when the postsynaptic neuron fires.
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The Nature of Learning
 Instrumental learning:
• A learning procedure whereby the effects
of a particular behavior in a particular
situation increase (reinforce) or decrease
(punish) the probability of the behavior;
also called operant conditioning.
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The Nature of Learning
 Reinforcing stimulus:
• An appetitive stimulus that follows a particular
behavior and thus makes the behavior become
more frequent.
 Punishing stimulus:
• An aversive stimulus that follows a particular
behavior and thus makes the behavior become
less frequent.
 Motor learning:
• Learning to make a new response.
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Learning and Synaptic Plasticity
 Induction of Long-Term Potentiation
 Long-term potentiation:
• A long-term increase in the excitability of a
neuron to a particular synaptic input caused by
repeated high-frequency activity of that input.
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Learning and Synaptic Plasticity
 Induction of Long-Term Potentiation
 Hippocampal formation:
• A forebrain structure of the temporal lobe,
constituting an important part of the limbic
system; includes the hippocampus proper
(Ammon’s horn), dentate gyrus, and subiculum.
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Learning and Synaptic Plasticity
 Induction of Long-Term Potentiation
 Entorhinal cortex:
• A region of the limbic cortex that provides the
major source of input to the hippocampal
formation.
 Granule cell:
• A small, granular cell; those found in the dentate
gyrus send axons to the field CA3 of the
hippocampus.
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Learning and Synaptic Plasticity
 Induction of Long-Term Potentiation
 Dentate gyrus:
• Part of the hippocampal formation; receives
inputs from the entorhinal cortex and projects to
the CA3 field of the hippocampus.
 Perforant path:
• The system of axons that travel from cells in the
entorhinal cortex to the dentate gyrus of the
hippocampal formation.
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Learning and Synaptic Plasticity
 Induction of Long-Term Potentiation
 Field CA3:
• Part of the hippocampus; receives inputs from
the dentate gyrus and projects to field CA3.
 Pyramidal cell:
• A category of large neurons with a pyramidal
shape; found in the cerebral cortex and Ammon’s
horn of the hippocampal formation.
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Learning and Synaptic Plasticity
 Induction of Long-Term Potentiation
 Field CA1:
• Part of the hippocampus; receives inputs from
field CA3 and projects out of the hippocampal
formation via the subiculum.
 Population EPSP:
• An evoked potential that represents the EPSPs of
a population of neurons.
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Learning and Synaptic Plasticity
 Role of NMDA Receptors
 Associative long-term potentiation:
• A long-term potentiation in which concurrent
stimulation of weak and strong synapses to a
given neuron strengthens the weak one.
 NMDA receptor:
• A specialized ionotropic glutamate receptor that
controls a calcium channel that is normally
blocked by Mg2 ions; involved in long-term
potentiation.
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Learning and Synaptic Plasticity
 Role of NMDA Receptors
 AP5:
• 2-Amino-5-phosphonopentanoate; a drug that
blocks NMDA receptors.
 AMPA receptor:
• An ionotropic glutamate receptor that controls a
sodium channel; when it’s open, it produces
EPSPs.
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Learning and Synaptic Plasticity
 Role of NMDA Receptors
 Dendritic spike:
• An action potential that occurs in the dendrite of
some types of pyramidal cells.
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Learning and Synaptic Plasticity
 Mechanisms of Synaptic Plasticity
 CaM-KII:
• Type II calcium-calmodulin kinase, an enzyme
that must be activated by calcium; may play a
role in the establishment of long-term potentiation.
 Nitric oxide synthase:
• An enzyme responsible for the production of
nitric oxide.
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Learning and Synaptic Plasticity
 Long-term Depression
 Long-term depression:
• A long-term decrease in the excitability of a
neuron to a particular synaptic input caused by
stimulation of the terminal button while the
postsynaptic membrane is hyperpolarized.
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Perceptual Learning
 Perceptual Short-term Memory
 Short-term memory:
• Memory for a stimulus that has just been
perceived.
 Delayed matching-to-sample task:
• A task that requires the subject to indicate which
of several stimuli has just been perceived.
 Paired-associate task
• A task that requires the subject to learn to
recognize pairs of stimuli.
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Instrumental Conditioning and Motor Learning
 Reinforcement
Neural Circuits Involved in Reinforcement
 Medial forebrain bundle (MFB):
• A fiber bundle that runs in a rostral-caudal
direction through the basal forebrain and lateral
hypothalamus; electrical stimulation of these
axons is reinforcing.
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Instrumental Conditioning and Motor Learning
 Reinforcement
Neural Circuits Involved in Reinforcement
 Ventral tegmental area (VTA):
• A group of dopaminergic neurons in the ventral
midbrain whose axons form the mesolimbic and
mesocortical system; plays a critical role in
reinforcement.
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Instrumental Conditioning and Motor Learning
 Reinforcement
Neural Circuits Involved in Reinforcement
 Nucleus accumbens:
• A nucleus of the basal forebrain near the septum;
receives dopamine-secreting terminal buttons
from neurons of the ventral tegmental area and is
thought to be involved in reinforcement and
attention.
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Instrumental Conditioning and Motor Learning
 Reinforcement
Detecting Reinforcing Stimuli
 Conditioned reinforcer:
• A previously neutral stimulus that has been
paired with an appetitive stimulus, which then
itself becomes capable of reinforcing a response.
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Instrumental Conditioning and Motor Learning
 Reinforcement
Detecting Reinforcing Stimuli
 Conditioned punisher:
• A previously neutral stimulus that has been
followed by an aversive stimulus, which then
itself becomes capable of punishing a response.
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