Download Chapter 14

Chapter 14
The Biology of Learning and Memory
Learning and Memory Definition

Learning
• A long term change in behavior as a function
of experiences.
 Memory
• The capacity to retain and
retrieve past experiences.
Types of Learning

Habituation
• A decrease in response following repeated exposure
to a non-threatening stimulus.

Sensitization
• An increase in reactivity to a stimulus following
exposure to an intense event.

Classical (Pavlovian)Conditioning
• Occurs through associations between an
environmental stimulus and a naturally occurring
stimulus.

Operant Conditioning
• Learning that occurs through rewards and
punishments for behavior.
Types of Learning:
Pavlovian Conditioning

Learning in which a neutral stimulus is paired
with a stimulus that elicits a reflex response
until the neutral stimulus elicits the reflex
response by itself.
• Unconditioned stimulus (US) - A stimulus that
involuntarily elicits a reflexive response.
• Unconditioned response (UR) - A reflexive reaction to
an unconditioned stimulus.
• Conditioned stimulus (CS) - An initially neutral
stimulus that eventually elicits a conditioned response
after pairing with a US.
• Conditioned response (CR) - A learned reaction to a
CS.
Classical Conditioning
Types of Learning:
Operant Conditioning

Learning how to behave to obtain
reinforcement
 Reinforcers - events or activities that increase the
frequency of the behavior that precedes that event or
activity.
 Punishers - events or activities that decrease the
frequency of the behavior that precedes them.
 Contingency -The specified relationship between a
behavior and its reinforcement or punishment.
Operant Conditioning
Models of Memory Storage and
Retrieval: Atkinson-Shiffrin model

An experience is sequentially stored in the sensory
register, and the short-term store, and the longterm store.
Models of Memory Storage and
Retrieval: Baddeley’s Rehearsal Systems
approach

An alternative to Atkinson-Shiffrin in which
Baddeley argued that memories go directly from
the sensory register to long-term storage.
Models of Memory Storage and
Retrieval: Craik and Lockhart

Craik and Lockhart - have a theory that
memories differ in the extent to which they have
been processed.
Types of Memories
Types of Memories
Declarative Memory

Memory whose formation does depend on
the hippocampal formation

Memory that can be verbally expressed
• Episodic memory
• Semantic memory
• Spatial memory

Slow-wave sleep facilitates consolidation of
declarative memories
Role of the Hippocampus
Input from motor and sensory association
cortexes and from subcortical regions such as
basal ganglia and amygdala
 Through efferent connections with these regions
modifies the memories being consolidated there,
linking them together
 A gradual process controlled by the hippocampus
transforms memories into long term storage in
the frontal cortex
 Before process completes, hippocampus is
necessary for retrieval

Procedural Memory






Memory whose formation does not depend on
the hippocampal formation
Collective term for stimulus-response,
perceptual, and motor memory
Non-declarative memories control behaviors
Learning to drive, type
REM sleep facilitates retention
of non-declarative memories
Ian Waterman
Perceptual Learning
Learning to recognize stimuli occurs when
synaptic changes take place in the appropriate
regions of the sensory cortex that establish
new neural circuits
 Learning to recognize sensory stimuli
• Primary visual cortex

 Ventral stream – object recognition
 Dorsal stream – object location

Other sensory information activate similar
areas of the association cortices
Perceptual Short-term memory
Activates the circuits and continues after the
stimuli disappears
 Successfully remembering short-term is a two
step process

• Filter out irrelevant information
• Maintain relevant information

Also in prefrontal cortex
• Manipulate and organize
• Strategies for retrieval

Delayed matching-to-sample task
• Faces – fusiform face area – face blindness
• Places – parahippocampal place area
The Anatomy of Learning and
Memory: Procedural Memory

Procedural or nondeclarative memory involves the
neocortex and neostriatum.

Basal ganglia structures needed for
procedural learning

Classical conditioning
of reflexes depends
on the cerebellum.
(Budson & Price, 2009)
The Memory Consolidation Process:
Hebb’s Cell Assemblies
Cell assembly - A circuit of neurons that become
active at the same time; serves as the site of
permanent memory.
 Reverberatory activity - Continued reactivation of
a neural circuit following an experience.

• Reverberatory activity is followed by physiological
changes that produce a relatively permanent record of
the event.

Phase sequence - interconnected cell assemblies
all activated at the same time in order to control
complex processes.
Structural Changes and Storing
Experiences
Experience enhances Ca2+ ion entry into the hippocampus (Lynch, 1986).
• Exposing more glutamate receptors to stimulation from other neurons,
making the postsynaptic neuron more sensitive.
• This may eventually cause changes in the terminal button and Lynch believes
this may be the biological basis of learning and memory.
Importance of the Hippocampus
• Damage results in memory
deficits
• Case of R.B.
• hippocampal damage
produced profound
anterograde amnesia
• Case of H.M.
• memories acquired before surgery were retained
suggesting that the hippocampus is involved in the
storage of declarative memory but is not the site of
storage.
• Some researchers have found episodic encoding in the
left frontal areas and episodic retrieval in the right frontal
regions.
PBS Nova – Aug 2009
Clive Wearing
Long Term Potentiation

A long term increase in the excitability of a neuron to
a particular stimulus due to the repeated highfrequency activity of that stimulus

A long-lasting strengthening of synapses between
nerve cells.

Long-term memories are thought to be based on LTP

Without LTP, learning some skills might be difficult or
impossible.
Characteristics of LTP

A brief, sensitizing stimulus is sufficient to produce LTP;
demonstrates that hippocampal neurons can change
synaptic responsivity following a single event.

LTP-changed synaptic responsivity is confined to a specific
neural pathway.

LTP can be produced by either a single stimulus or by the
convergence of stimuli that individually would not
produce LTP.

LTP can last for days or weeks, which suggests that it is
not just a temporary change in synaptic responsivity.
Long-Term Potentiation in the
Hippocampus


Long-term potentiation
is an increase in the
amplitude and duration
of EPSPs in response to
the test stimulus.
Three pathways involved
in LTP
• Perforant fiber pathway
• Mossy fiber pathway
• Schaffer collateral fiber
pathway
LTP and the NMDA Receptor




In the mossy fiber pathway, glutamate binds to
both the NMDA and non-NMDA receptors.
LTP apparently depends not on Ca2+ influx into
the postsynaptic receptor, but on Ca2+ influx
into the presynaptic cell after the LTP-inducing
stimulus.
Kandel refers to this as nonassociative - the
organism learns about the properties of a single
stimulus.
Habituation and sensitization are examples of
this type of learning.
Neuroplasticity in the Hippocampus

Neurogenesis - helps the brain to be modified in
adaptation to changing environmental conditions.
• Learning that involves the hippocampus results in new cells
surviving at a higher rate.
• The cells become part of neural circuits established by a
temporal-based learning experience.
• Enriched environments have been shown to increase the
size of an animal’s brain, their level of cortical ACh, and their
learning ability.
• Studies have shown enriched environments increase
hippocampal neurogenesis, even in adult
animals.
The Role of the Mediodorsal
Thalamus

Mediodorsal thalamus - A brain structure associated
with profound memory impairment.

People with Korsakoff’s syndrome often have atrophy
of cells in the mediodorsal thalamus caused by a
deficiency of Vitamin B1.

Loss of declarative rather than procedural memory.

Patients are unaware that they don’t remember; make
up stories (confabulation) to fill in the gaps.

Emotion is generally intact with medial temporal lobe
damage but patients with mediodorsal thalamic
damage tend to be emotionally flat and apathetic
Caudate Nucleus-Putamen
Memory System

Caudate nucleus
and putamen
control the ability
to develop
procedural
memory.
The Amygdala and Memory
Stimulation of the amygdala results in enhancing
the memory of a task
 Inhibition of the amygdala results in decreasing
the emotional arousal effects on memory.

Alzheimer’s Disease

A type of dementia characterized by
progressive neurological degeneration and a
profound deterioration of mental
functioning.
• Early onset - before age 65
• Risk factors include familial clustering of cases,
increasing
age, and Down
syndrome.
Alzheimer’s Disease
The Cellular Basis of
Alzheimer’s Disease

Cellular basis of AD
• Neurofibrillary tangles
• Senile plaques
• Amyloid beta protein
Alzheimer’s Disease:
Genetics





There is a link with chromosome 21
Another gene identified is ApoE on chromosome 19
Some people have one or two ApoE4 alleles and
have a greater risk of having late-onset AD.
The product of ApoE4 is not an effective antioxidant
for amyloid beta protein as are the products of
other alleles.
This may indicate a need to develop more effective
methods to increase antioxidants in the brains of
AD patients.