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Chapter 13: Biology of Learning and Memory

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Chapter 13: Biology of Learning and Memory Learning, Memory, Amnesia, and Brain Functioning Different kinds of brain damage result in different types of amnesia. – PowerPoint PPT presentation

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Title: Chapter 13: Biology of Learning and Memory


1
Chapter 13 Biology of Learning and Memory
2
Learning, Memory, Amnesia, and Brain Functioning
  • An early influential idea was that physical
    changes occur when something new is learned or a
    memory is formed.
  • Explanations was that connections grew between
    areas of the brain.
  • Led to the search for localized representations
    of memory

3
Learning, Memory, Amnesia, and Brain Functioning
  • Ivan Pavlov pioneered classical conditioning in
    which pairing of two stimuli changes the response
    to one of them.
  • A conditioned stimulus (CS) is paired with an
    unconditioned stimulus (UCS) which automatically
    results in an unconditioned response (UCR).
  • After several pairings, response can be elicited
    by the CS without the UCS,
  • New response is now called a conditioned response
    (CR).

4
Learning, Memory, Amnesia, and Brain Functioning
  • In operant conditioning, responses are followed
    by reinforcement or punishment that either
    strengthen or weaken the behavior.
  • Reinforcers are events that increase the
    probability that the response will occur again.
  • Punishment are events that decrease the
    probability that the response will occur again.

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Learning, Memory, Amnesia, and Brain Functioning
  • Pavlov believed that conditioning strengthened
    connections between the CS center and UCS center
    in the brain.
  • Karl Lashley set out to prove this by searching
    for such engrams, or physical representations of
    what had been learned.
  • Believed that a knife cut should abolish the
    newly learned response.

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Learning, Memory, Amnesia, and Brain Functioning
  • Lashleys studies attempted to see if disrupting
    certain connections between cortical brain areas
    would disrupt abilities to learn associations.
  • Found that learning and memory did not depend
    entirely on connections across the cortex
  • Also found that learning did not depend on a
    single area of the cortex.

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Learning, Memory, Amnesia, and Brain Functioning
  • Lashley proposed two key principles about the
    nervous system
  • Equipotentiality all parts of the cortex
    contribute equally to complex functioning
    behaviors (e.g. learning)
  • Mass action the cortex works as a whole, not as
    solitary isolated units.

11
Learning, Memory, Amnesia, and Brain Functioning
  • Richard F. Thompson et. al. suggested that the
    engram for classical conditioning is located in
    the cerebellum, not the cortex.
  • During conditioning, changes occur in the lateral
    interpositus nucleus (LIP) of the cerebellum
  • Responses increase as learning proceeds
  • necessary for learning and retention
  • However, a change in a brain area does not
    necessarily mean that learning took place in that
    area.

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Learning, Memory, Amnesia, and Brain Functioning
  • Suppression of activity in the LIP led to a
    condition in which the subject displayed no
    previous learning.
  • As suppression wore off, the animal began to
    learn at the same speed as animals that had no
    previous training.
  • But suppression of the red nucleus also led to a
    similar condition.
  • Later assumed that the learning did occur in the
    LIP, as it was the last structure that needed to
    be awake for learning to occur.

14
Learning, Memory, Amnesia, and Brain Functioning
  • Psychologist differentiate between learning and
    memory.
  • Hebb (1949) differentiated between two types of
    memory
  • Short-term memory memory of events that have
    just occurred.
  • Long-term memory memory of events from times
    further back.

15
Learning, Memory, Amnesia, and Brain Functioning
  • Differences between STM and LTM
  • Short-term memory has a limited capacity
    long-term memory does not.
  • Short-term memory fades quickly without
    rehearsal long-term memories persist.
  • Memories from long-term memory can be stimulated
    with a cue/ hint retrieval of memories lost from
    STM do not benefit from the presence of a cue.

16
Learning, Memory, Amnesia, and Brain Functioning
  • Researchers propose all information enters STM
    where the brain consolidates it into LTM.
  • Later research has weakened the distinction
    between STM and LTM
  • Working Memory
  • Proposed by Baddeley Hitch as an alternative to
    short-term memory.
  • Emphasis on temporary storage of information to
    actively attend to it and work on it for a period
    of time.

17
Learning, Memory, Amnesia, and Brain Functioning
  • Common test of working memory is the delayed
    response task.
  • Requires responding to something you heard or saw
    a short while ago.
  • Research points to the prefrontal cortex for the
    storage of this information
  • Brain may use elevated levels of calcium to
    potentiate later responses

18
Learning, Memory, Amnesia, and Brain Functioning
  • Older people often have impairments in working
    memory.
  • Changes in the prefrontal cortex assumed to be
    the cause.
  • Declining activity of the prefrontal cortex in
    the elderly is associated with decreasing memory.
  • Increased activity is indicative of compensation
    for other regions in the brain.

19
Learning, Memory, Amnesia, and Brain Functioning
  • Amnesia is the loss of memory.
  • Studies on amnesia help to clarify the
    distinctions between and among different kinds of
    memories and their mechanisms.
  • Different areas of the hippocampus are active
    during memory formation and retrieval.
  • Damage results in amnesia.

20
Learning, Memory, Amnesia, and Brain Functioning
  • H.M. is a famous case study in psychology who had
    his hippocampus removed to prevent epileptic
    seizures.
  • Afterwards H.M. had great difficulty forming new
    long-term memories.
  • STM or working memory remained intact.
  • Suggested that the hippocampus is vital for the
    formation of new long-term memories.

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Learning, Memory, Amnesia, and Brain Functioning
  • H.M. showed massive anterograde amnesia after the
    surgery.
  • Two major types of amnesia include
  • Anterograde amnesia the loss of the ability to
    form new memory after the brain damage
  • Retrograde amnesia the loss of memory events
    prior to the occurrence of the brain damage.

23
Learning, Memory, Amnesia, and Brain Functioning
  • Patient HM also displayed greater implicit than
    explicit memory.
  • Explicit memory deliberate recall of
    information that one recognizes as a memory.
  • Implicit memory the influence of recent
    experience on behavior without realizing one is
    using memory.

24
Learning, Memory, Amnesia, and Brain Functioning
  • H.M. had difficulty with episodic memory and
    declarative memory.
  • Episodic memory ability to recall single events.
  • Declarative memory ability to state a memory
    into words.
  • H.M.s procedural memory remained intact.
  • Procedural memory ability to develop motor
    skills (remembering or learning how to do things).

25
Learning, Memory, Amnesia, and Brain Functioning
  • Research of the function of the hippocampus
    suggests the following
  • The hippocampus is critical for declarative
    memory functioning (especially episodic).
  • The hippocampus is especially important for
    spatial memory.
  • The hippocampus is especially important for
    configural learning and binding.

26
Learning, Memory, Amnesia, and Brain Functioning
  • Research in the role of the hippocampus in
    episodic memory shows damage impairs abilities on
    two types of tasks
  • Delayed matching-to-sample tasks a subject sees
    an object and must later choose the object that
    matches.
  • Delayed non-matching-to-sample tasks subject
    sees an object and must later choose the object
    that is different than the sample.

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Learning, Memory, Amnesia, and Brain Functioning
  • Damage to the hippocampus also impairs abilities
    on spatial tasks such as
  • Radial mazes a subject must navigate a maze
    that has eight or more arms with a reinforcer at
    the end.
  • Morris water maze task a rat must swim through
    murky water to find a rest platform just
    underneath the surface.

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31
Learning, Memory, Amnesia, and Brain Functioning
  • Hippocampus may also be important for contextual
    learning
  • Remembering the detail and context of an event
  • suggests that the hippocampus is important in the
    process of consolidation.
  • Damage to the hippocampus impairs recent learning
    more than older learning.
  • The more consolidated a memory becomes, the less
    it depends on the hippocampus.

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Learning, Memory, Amnesia, and Brain Functioning
  • Reverberating circuits of neuronal activity were
    thought to be the mechanisms of consolidation.
  • Consolidation is also influenced by the passage
    of time and emotions.
  • Small to moderate amounts of cortisol activate
    the amygdala and hippocampus where they enhance
    storage and consolidation of recent experiences.
  • Prolonged stress impairs memory.

34
Learning, Memory, Amnesia, and Brain Functioning
  • Different kinds of brain damage result in
    different types of amnesia.
  • Two common types of brain damage include
  • Korsakoffs syndrome
  • Alzheimers disease

35
Learning, Memory, Amnesia, and Brain Functioning
  • Korsakoffs syndrome brain damage caused by
    prolonged thiamine (vitamin B1) deficiency
  • impedes the ability of the brain to metabolize
    glucose.
  • Leads to a loss of or shrinkage of neurons in the
    brain.
  • Often due to chronic alcoholism.
  • Symptoms include apathy, confusion, and
    forgetting and confabulation (taking guesses to
    fill in gaps in memory).

36
Learning, Memory, Amnesia, and Brain Functioning
  • Alzheimers disease is associated with a
    gradually progressive loss of memory often
    occurring in old age.
  • Affects 50 of people over 85.
  • Early onset seems to be influenced by genes, but
    99 of cases are late onset.
  • About half of all patients with late onset have
    no known relative with the disease.

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38
Learning, Memory, Amnesia, and Brain Functioning
  • Alzheimers disease is associated with an
    accumulation and clumping of the following brain
    proteins
  • Amyloid beta protein 42 which produces widespread
    atrophy of the cerebral cortex, hippocampus and
    other areas.
  • An abnormal form of the tau protein, part of the
    intracellular support system of neurons.

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40
Learning, Memory, Amnesia, and Brain Functioning
  • Accumulation of the tau protein results in
  • Plaques structures formed from degenerating
    neurons.
  • Tangles structures formed from degenerating
    structures within a neuronal body.

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Learning, Memory, Amnesia, and Brain Functioning
  • A major area of damage is the basal forebrain and
    treatment includes enhancing acetylcholine
    activity.
  • One experimental treatment includes the
    stimulation of cannabinoid receptors that limits
    overstimulation by glutamate.
  • Research with mice suggests the possibility of
    immunizing against Alzheimers by stimulating the
    production of antibodies against amyloid beta
    protein.

43
Learning, Memory, Amnesia, and Brain Functioning
  • Lessons from studying amnesiac patients include
  • There can be deficiencies of very different
    aspects of memory.
  • There are independent kinds of memory.
  • Various kinds of memory depend on different brain
    areas.

44
Learning, Memory, Amnesia, and Brain Functioning
  • Other subcortical brain areas and the cortex
    important in learning
  • Amygdala associated with fear learning
  • Parietal lobe associated with piecing information
    together
  • anterior and inferior region of the temporal lobe
    and semantic memory
  • semantic dementia (loss of semantic memory)

45
Learning, Memory, Amnesia, and Brain Functioning
  • Other areas of the cortex important in learning
    (cont)
  • Prefrontal cortex and learning about rewards and
    punishments
  • Basal ganglia, anterior cingulate cortex also
    involved

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Storing Information in the Nervous System
  • Activity in the brain results in physical
    changes.
  • Patterns of activity leave a path of physical
    changes.
  • Not every change is a specific memory as was once
    originally believed.
  • Many ideas originally believed to be true have
    been refined.

48
Storing Information in the Nervous System
  • A Hebbian synapse occurs when the successful
    stimulation of a cell by an axon leads to the
    enhanced ability to stimulate that cell in the
    future.
  • Increases in effectiveness occur because of
    simultaneous activity in the presynaptic and
    postsynaptic neurons.
  • Such synapses may be critical for many kinds of
    associative learning.

49
Storing Information in the Nervous System
  • Studies of how physiology relates to learning
    often focus on invertebrates and try to
    generalize to vertebrates.
  • The aplysia is a slug-like invertebrate that is
    often studied due to its large neurons.
  • This allows researchers to study basic processes
    such as
  • Habituation
  • Sensitization

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Storing Information in the Nervous System
  • Habituation is a decrease in response to a
    stimulus that is presented repeatedly and
    accompanied by no change in other stimuli.
  • Depends upon a change in the synapse between the
    sensory neurons and the motor neurons.
  • Sensory neurons fail to excite motor neurons as
    they did previously.

53
Storing Information in the Nervous System
  • Sensitization is an increase in response to a
    mild stimulus as a result to previous exposure to
    more intense stimuli.
  • Changes at identified synapses include
  • Serotonin released from a facilitating neuron
    blocks potassium channels in the presynaptic
    neuron.
  • Prolonged release of transmitter from that neuron
    results in prolonged sensitization.

54
Storing Information in the Nervous System
  • Long-term Potentiation (LTP) occurs when one or
    more axons bombard a dendrite with stimulation.
  • Leaves the synapse potentiated for a period of
    time and the neuron is more responsive

55
Storing Information in the Nervous System
  • Properties of LTP that suggest it as a cellular
    basis of learning and memory include
  • Specificity
  • Cooperativity
  • Associativity

56
Storing Information in the Nervous System
  • Specificity only synapses onto a cell that have
    been highly active become strengthened.
  • Cooperativity simultaneous stimulation by two
    or more axons produces LTP much more strongly
    than does repeated stimulation by a single axon.
  • Associativity pairing a weak input with a
    strong input enhances later responses to a weak
    input.

57
Storing Information in the Nervous System
  • Long-term depression (LTD) is a prolonged
    decrease in response at a synapse that occurs
    when axons have been active at a low frequency.
  • The opposite of LTP

58
Storing Information in the Nervous System
  • Biochemical mechanisms of LTP are known to depend
    on changes at glutamate and GABA primarily in
    the postsynaptic neuron
  • This occurs at several types of receptor sites
    including the ionotropic receptors
  • AMPA receptors
  • NMDA receptors

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Storing Information in the Nervous System
  • LTP in hippocampal neurons occurs as follows
  • Repeated glutamate excitation of AMPA receptors
    depolarizes the membrane.
  • The depolarization removes magnesium ions that
    had been blocking NMDA receptors.
  • Glutamate is then able to excite the NMDA
    receptors, opening a channel for calcium ions to
    enter the neuron.

61
Storing Information in the Nervous System
  • Entry of calcium through the NMDA channel
    triggers further changes.
  • Activation of a protein that sets in motion a
    series of events occurs.
  • More AMPA receptors are built and dendritic
    branching is increased.
  • These changes increase the later responsiveness
    of the dendrite to incoming glutamate.

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Storing Information in the Nervous System
  • Changes in presynaptic neuron can also cause LTP.
  • Extensive stimulation of a postsynaptic cell
    causes the release of a retrograde transmitter
    that travels back to the presynaptic cell to
    cause the following changes
  • Decrease in action potential threshold
  • Increase neurotransmitter release of
  • Expansion of the axons.
  • Transmitter release from additional sites.

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Storing Information in the Nervous System
  • LTP reflects increased activity by the
    presynaptic neuron and increased responsiveness
    by the postsynaptic neuron
  • Understanding the mechanisms of changes that
    enhance or impair LTP may lead to drugs that
    improve or block memory.
  • Increasing production of hormones increased by
    LTP
  • Ginkgo biloba
  • Etc.
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