PS263 Lecture Notes - Lecture 14: Neurotrophin, Growth Factor, Amygdala

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27 Mar 2017
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Chapter 12: The Biology of Learning and Memory
12.1: Learning, Memory, and Amnesia
Localized Representations of Memory
Psychologists have traditionally distinguished two major categories, classical and
instrumental conditioning.
Pavlov pioneered the investigation of what we call classical conditioning in which pairing
two stimuli changes the response to one of them. The experimenter starts by presenting a
conditioned stimulus (CS), which initially elicits no response of note, and then presents the
unconditioned stimulus (UCS), which automatically elicits the unconditioned response
(UCR).
After pairings of the CS and the UCS the individual begins making a new learned
conditioned response(CR)
In instrumental conditioning also known as operat oditioig, a idiidual’s respose
leads to a reinforcer or punishment.
A reinforcer is any event that increases the future probability of the response. A
punishment is an event that suppresses the frequency of the response
Difference between classical and instrumental conditioning is that in instrumental
oditioig the idiidual’s respose deteries the outoe, hereas i lassial
oditioig the CS ad UCS our at ertai ties regardless of the idiidual’s ehaior
Lashle’s Searh for the Engram
Pavlov proposed the simple hypothesis that classical conditioning reflects a strengthened
connection between a CS center and a UCS center in the brain. The strengthened
connections lets any excitation of the CS center to flow to the UCS center, evoking a
conditioned response
Lashley was searching for the engram- the physical representation of what has been
learned. (a connection between two brain areas would be an example)
He reasoned that if learning depends on new or strengthened connections between 2 brain
areas, a knife cut somewhere in the brain should interrupt that connection and abolish the
learned response.
No knife cut repaired the rats performances. Learning did not depend on connections across
the cortex
Learning and memory did not rely on a single cortical area. Two principles about the NS:
o Equipotentiality-all parts of the cortex contribute equally to complex behaviors such
as learning, and any part of the cortex can substitute for any other
o Mass action: the cortex works and more cortex is better
Lashle’s olusios rested o ueessar assuptios: a that the ereral orte is the
best or only place to search for an engram, and (b) that studying one example of learning is
just as good as studying any other one.
The Modern Search for the Engram
Thopso ad his olleagues used a sipler task tha Lashle’s ad sought that the egra
of memory not in the cerebral cortex but in the cerebellum. Studied eyelid responses in
rabbits
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Thopso’s researh idetified oe uleus of the cerebellum, the lateral interpositus
nucleus (LIP) as essential for learning.
When the red nucleus was suppressed, the rabbits again showed strong learning responses.
Temporarily prevented the response but did not prevent learning.
Learning did not require activity in the red nucleus, research found that the red nucleus
does contribute to learning in some circumstances
Types of Memory
Short-Term and Long-Term Memory
Short-Term memory and long-term memory differ in their capacity.
Short-term memory depends on rehearsal. Once you have forgotten something, it is lost.
Storing memories in short-term for a sufficient period of time made it possible for the brain
to consolidate it into long-term memories.
Changing Views of Consolidation
Many Short-term memories are not simply temporary stores on their way to being long-
term memories
Small to moderate amounts of cortisol activate the amygdala and hippocampus, where they
enhance the storage and consolidation of recent experiences
Working Memory
Working memory to refer to the way we store information while we are working with it
A common test of working memory is the delayed-response task where you response to
something that you have heard a short while ago
Damage to the prefrontal cortex impairs performance.
The Hippocampus
Amnesia is memory loss.
People with Hippocampal Damage
H.M was suffering epileptic seizures so they removed the hippocampus and some nearby
structures
Hippocampus are active during the formation of memories and later recall
H.M suffered a severe memory impairment.
Anterograde and Retrograde Amnesia
After the surger H.M’s itellet ad laguage ailities reaied itat, ad persoalit
remained the same except for emotional placidity
He suffered from massive anterograde amnesia where he could not form memories for
events that occurred after brain damage
He also suffered from retrograde amnesia where he could not remember events that
occurred before the brain damage
Intact Working Memory
His short-term or working memory remained intact.
Most patients that have severe amnesia show normal working memory
Impaired Storage of Long-Term Memory
He showed normal working memory but as soon as he was distracted his memory was gone
within seconds
H.M formed a few new weak semantic memories- that is, memories of factual information
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