Chapter 12
Learning
1
Three Types of Behavior

Reflexes


Instincts


involuntary responses to stimuli.
stereotyped responses triggered by environmental
stimuli.
Learning

a relatively permanent change in behavior due to
experience.
© Renee Purse/Photo Researchers, Inc.
2
Types of Learning

Associative learning involves a connection
between two elements or events.



Classical conditioning
Operant conditioning
Nonassociative learning involves change in
the magnitude of response to environmental
events.


Habituation
Sensitization
3
Nonassociative learning

Habituation



The response to steady or repeated (harmless)
stimulus decreases over time.
Example: You don’t hear your air conditioner after
it’s been running awhile.
Sensitization


The experience of one stimulus heightens the
response to a subsequent stimulus.
Example: People are “jumpy” following natural
disasters, like earthquakes.
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Using Aplysia Californica to Study Learning




The gill is used for breathing.
The gill can be covered with
the mantle shelf.
Waste and seawater are
released through the siphon.
The gill-withdrawal reflex
occurs when touching the
siphon produces a retraction
of the gill.
5
Using Aplysia Californica to Study Learning


Anatomy of gillwithdrawal reflex
This reflex can show
habituation
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Why does habituation occur?
Possible Hypotheses
1.
2.
3.
Do sensory neurons in the siphon become less
responsive?
Does the gill muscle lose its ability to contract?
Do changes occur at
the synapses between
the sensory and motor
neurons?
Daniel L. Geiger/SNAP
7
Kandel’s Explanation
of Habituation Aplysia
8
Kandel’s Explanation
Sensitization in Aplysia
9
Kandel’s Explanation
Sensitization in Aplysia
10
Long-term Changes in Habituation
and Sensitization

Normal Aplysia showed
1300 axon terminals on
sensory neurons.


Aplysia experiencing
sensitization had 2800
terminals.
Aplysia experiencing
habituation had 800
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terminals.
Associative
learning
Classical Conditioning
 Basic Procedure
12
Classical Conditioning in Aplysia
13
Conditioned Emotional Responses
and the Amygdala

Typical experiment for conditioned emotional response

Tone (CS+) followed by shock (UCS) results in reduced feeding
(CR) in rats.
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Conditioned Emotional Responses
and the Amygdala

Evidence that amygdala involved in this type of
learning



Lesions of the basolateral nucleus of the amygdala prevent
this learning.
Recording during training shows an increased response of
the amygdala to the tone.
Blocking NMDA receptors in the amygdala prevents learning
of conditioned emotional responses.
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Hebb rule
The hypothesis that the cellular basis of learning
involves strengthening of a synapse that is
repeatedly active when the postsynaptic neuron
fires.
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Associative learning
Instrumental learning (operant
conditioning):



A learning procedure whereby the effects of a
particular behavior in a particular situation increase
(reinforce) or decrease (punish) the probability of
the behavior.
Association between a stimulus and a response
Not automatic
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Instrumental Learning
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