Learning and Memory

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Learning and Memory
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17 Learning and Memory

• Functional Perspectives on Memory
• There Are Several Kinds of Memory and Learning
• Memory Has Temporal Stages Short, Intermediate,
  and Long
• Successive Processes Capture, Store, and Retrieve
  Information in the Brain
• Different Brain Regions Process Different Aspects
  of Memory

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17 Learning and Memory

• Neural Mechanisms of Memory
• Memory Storage Requires Neuronal Remodeling
• Invertebrate Nervous Systems Show Plasticity
• Synaptic Plasticity Can Be Measured in Simple
  Hippocampal Circuits

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17 Learning and Memory

• Neural Mechanisms of Memory (cont'd)
• Some Simple Learning Relies on Circuits in the
  Mammalian Cerebellum
• In the Adult Brain, Newly Born Neurons May Aid
  Learning
• Learning and Memory Change as We Age

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17 Functional Perspectives on Memory

• Learning is the process of acquiring new
  information.
• Memory is
• The ability to store and retrieve information.
• The specific information stored in the brain.

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17 There Are Several Kinds of Memory and Learning

• Patient H.M. suffers from amnesia, or memory
  impairment.
• Retrograde amnesia is the loss of memories formed
  before onset of amnesia.
• Anterograde amnesia is the inability to form
  memories after onset of a disorder.

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17 There Are Several Kinds of Memory and Learning

• Damage to the hippocampus can produce memory
  deficits.
• H.M.s surgery removed the amygdala, the
  hippocampus, and some cortex.
• H.M.s memory deficit was confined to verbal
  tasks.

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Figure 17.1 Brain Tissue Removed from Henry
Molaison (Patient H.M.)
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Figure 17.2 Henrys Performance on a
Mirror-Tracing Task
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17 There Are Several Kinds of Memory and Learning

• Two kinds of memory
• Declarative memory deals with what facts and
  information acquired through learning that can be
  stated or described.
• Nondeclarative (procedural) memory deals with
  how shown by performance rather than
  recollection.

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Figure 17.3 Two Main Kinds of Memory
Declarative and Nondeclarative
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17 There Are Several Kinds of Memory and Learning

• Damage to other areas can also cause memory loss.
• Patient N.A. has amnesia due to accidental damage
  to the dorsomedial thalamus.
• Like Henry Molaison, he has short-term memory but
  cannot form declarative long-term memories.

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Figure 17.4 The Brain Damage in Patient N.A.
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17 There Are Several Kinds of Memory and Learning

• Korsakoffs syndrome is a memory deficiency
  caused by lack of thiamine seen in chronic
  alcoholism.
• Brain damage occurs in mammillary bodies and
  basal frontal lobes.
• Patients often confabulate fill in a gap in
  memory with a falsification.

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17 There Are Several Kinds of Memory and Learning

• Two subtypes of declarative memory
• Semantic memory generalized memory.
• Episodic memory detailed autobiographical
  memory.
• Patient K.C. cannot retrieve personal (episodic)
  memory due to accidental damage to the cortex.

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17 There Are Several Kinds of Memory and Learning

• Three subtypes of nondeclarative memory
• Skill learning learning to perform a task
  requiring motor coordination.
• Priming repetition priming a change in
  stimulus processing due to prior exposure to the
  stimulus.
• Conditioning the association of two stimuli, or
  of a stimulus and a response.

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Figure 17.5 Subtypes of Declarative and
Nondeclarative Memory
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17 There Are Several Kinds of Memory and Learning

• Nonassociative learning involves a single
  stimulus presented once or repeated.
• Three types of nonassociative learning
• Habituation a decreased response to repeated
  presentations of a stimulus.
• Dishabituation restoration of response
  amplitude after habituation.
• Sensitization prior strong stimulation
  increases response to most stimuli.

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17 There Are Several Kinds of Memory and Learning

• Associative learning involves relations between
  events.
• In classical conditioning Pavlovian
  conditioning a neutral stimulus is paired with
  another stimulus that elicits a response.
• Eventually the neutral stimulus by itself will
  elicit the response.

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17 There Are Several Kinds of Memory and Learning

• In instrumental conditioning or operant
  conditioning an association is made between
• Behavior (the instrumental response).
• The consequences of the behavior (the reward).

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17 Memory Has Temporal Stages Short,
Intermediate, and Long

• Iconic memories are the briefest and store
  sensory impressions.
• Short-term memories (STMs) usually last only for
  seconds, or throughout rehearsal.
• Short-term memory is also known as working memory.

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17 Memory Has Temporal Stages Short,
Intermediate, and Long

• Working memory can be subdivided into three
  components, all supervised by a central
  executive
• Phonological loop contains auditory
  information.
• Visuospatial sketch pad holds visual
  impressions.
• Episodic buffer contains more integrated
  information.

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17 Memory Has Temporal Stages Short,
Intermediate, and Long

• An intermediate-term memory (ITM) outlasts a STM,
  but is not permanent.
• Long-term memories (LTMs) last for days to years.

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17 Memory Has Temporal Stages Short,
Intermediate, and Long

• Mechanisms differ for STM and LTM storage, but
  are similar across species.
• The primacy effect is the higher performance for
  items at the beginning of a list (LTM).
• The recency effect shows better performance for
  the items at the end of a list (STM).

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Figure 17.6 Serial Position Curves from
Immediate-Recall Experiments
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17 Memory Has Temporal Stages Short,
Intermediate, and Long

• Long-term memory has a large capacity, but can be
  altered.
• The memory trace, or record of a learning
  experience, can be affected by other events
  before or after.
• Each time a memory trace is activated and
  recalled, it is subject to changes.

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17 Successive Processes Capture, Store, and
Retrieve Information in the Brain

• A functional memory system incorporates three
  aspects
• Encoding sensory information is encoded into
  short-term memory.
• Consolidation information may be consolidated
  into long-term storage.
• Retrieval stored information is retrieved.

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Figure 17.7 Hypothesized Memory Processes
Encoding, Consolidation, and Retrieval
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17 Successive Processes Capture, Store, and
Retrieve Information in the Brain

• Multiple brain regions are involved in encoding,
  as shown by fMRI.
• For recalling pictures, the right prefrontal
  cortex and parahippocampal cortex in both
  hemispheres are activated.
• For recalling words, the left prefrontal cortex
  and the left parahippocampal cortex are activated.

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17 Successive Processes Capture, Store, and
Retrieve Information in the Brain

• Consolidation of memory involves the hippocampus
  but the hippocampal system does not store
  long-term memory.
• LTM storage occurs in the cortex, near where the
  memory was first processed and held in short-term
  memory.

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Figure 17.8 Encoding, Consolidation, and
Retrieval of Declarative Memories
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17 Successive Processes Capture, Store, and
Retrieve Information in the Brain

• The process of retrieving information from LTM
  can cause memories to become unstable and
  susceptible to to disruption or alteration.
• Reconsolidation is the return of a memory trace
  to stable long-term storage, after recall.

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17 Successive Processes Capture, Store, and
Retrieve Information in the Brain

• Strong emotions can enhance memory formation and
  retrieval.
• Many compounds participate acetylcholine,
  epinephrine, norepinephrine, vasopressin, the
  opioids, and GABA.
• Drugs that are agonists or antagonists of these
  can be involved.

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17 Successive Processes Capture, Store, and
Retrieve Information in the Brain

• In posttraumatic stress disorder (PTSD), memories
  produce a stress hormone response that further
  reinforces the memory.
• Treatments that can block chemicals acting on the
  basolateral amygdala may alter the effect of
  emotion on memories.

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Box 17.2 The Amygdala and Memory
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17 Different Brain Regions Process Different
Aspects of Memory

• Testing declarative memories in monkeys
• Delayed non-matching-to-sample task must choose
  the object that was not seen previously.
• Medial temporal lobe damage causes impairment on
  this task.

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Figure 17.9 The Delayed Non-Matching-to-Sample
Task
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Figure 17.10 Memory Performance after Medial
Temporal Lobe Lesions
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17 Different Brain Regions Process Different
Aspects of Memory

• Imaging studies confirm the importance of medial
  temporal (hippocampal) and diencephalic regions
  in forming long-term memories.
• Both are activated during encoding and retrieval,
  but long-term storage depends on the cortex.

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17 Different Brain Regions Process Different
Aspects of Memory

• Episodic and semantic memories are processed in
  different areas.
• Episodic (autobiographical) memories cause
  greater activation of the right frontal and
  temporal lobes.

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Figure 17.11 My Story versus Your Story
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17 Different Brain Regions Process Different
Aspects of Memory

• Early research indicated that animals form a
  cognitive map a mental representation of a
  spatial relationship.
• Latent learning has taken place but has not been
  demonstrated in performance tasks.

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Figure 17.12 Biological Psychologists at Work
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17 Different Brain Regions Process Different
Aspects of Memory

• The hippocampus is also important in spatial
  learning.
• It contains place cells that become active when
  in, or moving toward, a particular location.
• Grid cells and border cells are neurons that fire
  when animal is at an intersection or perimeter of
  an abstract grid map.

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17 Different Brain Regions Process Different
Aspects of Memory

• In rats, place cells in the hippocampus are more
  active as the animal moves toward a particular
  location.
• In monkeys, spatial view cells in the hippocampus
  respond to what the animal is looking at.

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17 Different Brain Regions Process Different
Aspects of Memory

• Comparisons of behaviors and brain anatomy show
  that increased demand for spatial memory results
  in increased hippocampal size in mammals and
  birds.
• In food-storing species of birds, the hippocampus
  is larger but only if used to retrieve stored
  food.

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17 Different Brain Regions Process Different
Aspects of Memory

• Spatial memory and hippocampal size can change
  within the life span.
• In some species, there can be be sex differences
  in spatial memory, depending on behavior.
• Polygynous male meadow voles travel further and
  have a larger hippocampus than females or
  monogamous pine vole males.

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Figure 17.13 Sex, Memory, and Hippocampal Size
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17 Different Brain Regions Process Different
Aspects of Memory

• Imaging studies help to understand learning and
  memory for different skills
• Sensorimotor skills, such as mirror-tracing.
• Perceptual skills learning to read
  mirror-reversed text.
• Cognitive skills planning and problem solving.

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17 Different Brain Regions Process Different
Aspects of Memory

• Imaging studies of repetition priming show
  reduced bilateral activity in the
  occipitotemporal cortex, related to perceptual
  priming.
• Perceptual priming reflects prior processing of
  the form of the stimulus.

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17 Different Brain Regions Process Different
Aspects of Memory

• During conceptual priming, there is reduced
  activity compared to baseline in only the left
  frontal cortex.
• Conceptual priming reflects the meaning of the
  stimulus.

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17 Different Brain Regions Process Different
Aspects of Memory

• Imaging of conditioned responses can show changes
  in activity.
• PET scans made during eye-blink tests show
  increased activity in several brain regions, but
  not all may be essential.
• Patients with unilateral cerebellar damage can
  acquire the conditioned eye-blink response only
  on the intact side.

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17 Different Brain Regions Process Different
Aspects of Memory

• Different brain regions are involved with
  different attributes of working memories such as
  space, time, or sensory perception.
• Memory tasks assess the contributions of each
  brain region.

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17 Different Brain Regions Process Different
Aspects of Memory

• The eight-arm radial maze is used to test spatial
  location memory.
• Rats must recognize and enter an arm that they
  have entered recently to receive a reward.
• Only lesions of the hippocampus produce a deficit
  in this predominantly spatial task.

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Figure 17.14 Tests of Specific Attributes of
Memory (Part 1)
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17 Different Brain Regions Process Different
Aspects of Memory

• In a memory test of motor behavior the animal
  must remember whether it made a left or right
  turn previously.
• If it turns the same way as before it receives a
  reward.
• Only animals with lesions to the caudate nucleus
  showed deficits.

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Figure 17.14 Tests of Specific Attributes of
Memory (Part 2)
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17 Different Brain Regions Process Different
Aspects of Memory

• Sensory perception can be measured by the object
  recognition task.
• Rats must identify which stimulus in a pair is
  novel.
• This task depends on the extrastriate cortex.

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Figure 17.14 Tests of Specific Attributes of
Memory (Part 3)
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17 Different Brain Regions Process Different
Aspects of Memory

• Interim summary of brain regions involved in
  learning and memory
• Many brain regions are involved.
• Different forms of memory are mediated by at
  least partly different mechanisms and brain
  structures.
• The same brain structure may be involved in many
  forms of learning.

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Figure 17.15 Brain Regions Involved in Different
Kinds of Learning and Memory
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17 Neural Mechanisms of Memory

• Molecular, synaptic, and cellular events store
  information in the nervous system
• New learning and memory formation can involve new
  neurons, new synapses, or changes in synapses in
  response to biochemical signals.
• Neuroplasticity (or neural plasticity) is the
  ability of neurons and neural circuits to be
  remodeled by experience or environment.

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17 Memory Storage Requires Neuronal Remodeling

• Sherrington speculated that alterations in
  synapses were the basis for learning.
• Hebb proposed that when two neurons are
  repeatedly activated together, their synaptic
  connection will become stronger.
• Cell assemblies - ensembles of neurons - linked
  via Hebbian synapses could store memory traces.

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17 Memory Storage Requires Neuronal Remodeling

• Physiological changes at synapses may store
  information.
• Changes can be presynaptic, or postsynaptic, or
  both.
• Changes can include increased neurotransmitter
  release, or effectiveness of receptors.

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17 Memory Storage Requires Neuronal Remodeling

• Synaptic changes can be measured physiologically,
  and may be presynaptic, postsynaptic, or both.
• Changes include increased neurotransmitter
  release and/or a greater effect due to changes in
  receptors.

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Figure 17.16 Synaptic Changes That May Store
Memories (Part 1)
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17 Memory Storage Requires Neuronal Remodeling

• Changes in the rate of inactivation of
  transmitter would also increase effects.
• Inputs from other neurons might increase or
  decrease neurotransmitter release.

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17 Memory Storage Requires Neuronal Remodeling

• Structural changes at the synapse may provide
  long-term storage.
• New synapses could form or some could be
  eliminated with training.
• Training might also lead to synaptic
  reorganization.

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Figure 17.16 Synaptic Changes That May Store
Memories (Part 2)
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17 Memory Storage Requires Neuronal Remodeling

• Lab animals living in a complex environment
  demonstrated biochemical and anatomical brain
  changes.
• Three housing conditions
• Standard condition (SC)
• Impoverished (or isolated) condition (IC)
• Enriched condition (EC)

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Figure 17.17 Experimental Environments to Test
the Effects of Enrichment on Learning and Brain
Measures
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17 Memory Storage Requires Neuronal Remodeling

• Animals housed in EC developed
• Heavier, thicker cortex.
• Enhanced cholinergic activity.
• Larger cortical synapses.
• Altered gene expression.
• Enhanced recovery from brain damage.

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17 Memory Storage Requires Neuronal Remodeling

• EC also increases growth in dendrites
• More dendritic spines suggesting more synapses.
• Increased dendritic branching, especially on
  basal dendrites, nearer the cell body.

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Figure 17.18 Measurement of Dendritic Branching
(Part 1)
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Figure 17.18 Measurement of Dendritic Branching
(Part 2)
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17 Invertebrate Nervous Systems Show Plasticity

• Aplysia is used to study plastic synaptic changes
  in neural circuits.
• The advantages of Aplysia
• Has fewer nerve cells.
• Can create detailed circuit maps for particular
  behaviors little variation between individuals.

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17 Invertebrate Nervous Systems Show Plasticity

• Habituation is studied in Aplysia.
• Squirts of water on its siphon causes it to
  retract its gill.
• After repeated squirts, the animal retracts the
  gills less it has learned that the water poses
  no danger.

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Figure 17.19 The Sea Slug Aplysia
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17 Invertebrate Nervous Systems Show Plasticity

• The habituation is caused by synaptic changes
  between the sensory cell in the siphon and the
  motoneuron that retracts the gill.
• Less transmitter released in the synapse results
  in less retraction.

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Figure 17.20 Synaptic Plasticity Underlying
Habituation in Aplysia (Part 1)
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17 Invertebrate Nervous Systems Show Plasticity

• Over several days the animal habituates faster,
  representing long-term habituation.
• The number of synapses between the sensory cell
  and the motoneuron is reduced.

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Figure 17.20 Synaptic Plasticity Underlying
Habituation in Aplysia (Part 2)
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17 Synaptic Plasticity Can Be Measured in Simple
Hippocampal Circuits

• Long-term potentiation (LTP) a stable and
  enduring increase in the effectiveness of
  synapses.
• Tetanus a brief increase of electrical
  stimulation that triggers thousands of axon
  potentials.

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17 Synaptic Plasticity Can Be Measured in Simple
Hippocampal Circuits

• Synapses in LTP behave like Hebbian synapses
• Tetanus drives repeated firing.
• Postsynaptic targets fire repeatedly due to the
  stimulation.
• Synapses are stronger than before.

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17 Synaptic Plasticity Can Be Measured in Simple
Hippocampal Circuits

• LTP occurs at several sites in the hippocampal
  formation formed by the hippocampus, the
  dentate gyrus and the subiculum.
• Regions CA1 and CA3 are most often studied.

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Figure 17.21 Long-Term Potentiation Occurs in
the Hippocampus (Part 1)
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Figure 17.21 Long-Term Potentiation Occurs in
the Hippocampus (Part 2)
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Figure 17.21 Long-Term Potentiation Occurs in
the Hippocampus (Part 3)
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17 Synaptic Plasticity Can Be Measured in Simple
Hippocampal Circuits

• The CA1 region has both NMDA and AMPA receptors.
• Glutamate first activates AMPA receptors.
• NMDA receptors do not respond until enough AMPA
  receptors are stimulated and the neuron is
  partially depolarized.

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17 Synaptic Plasticity Can Be Measured in Simple
Hippocampal Circuits

• NMDA receptors at rest have a magnesium ion
  (Mg2) block on their calcium (Ca2) channels.
• After partial depolarization, the block is
  removed and the NMDA receptor allows Ca2 to
  enter in response to glutamate.

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Figure 17.22 Roles of NMDA and AMPA Receptors in
the Induction of LTP in CA1 Region (Part 1)
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Figure 17.22 Roles of NMDA and AMPA Receptors in
the Induction of LTP in CA1 Region (Part 2)
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Figure 17.22 Roles of NMDA and AMPA Receptors in
the Induction of LTP in CA1 Region (Part 3)
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17 Synaptic Plasticity Can Be Measured in Simple
Hippocampal Circuits

• The large Ca2 influx activates certain protein
  kinases enzymes that add phosphate groups to
  protein molecules.
• One protein kinase is CaMKII it affects AMPA
  receptors in several ways
• Causes more AMPA receptors to be produced and
  inserted in the postsynaptic membrane.

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17 Synaptic Plasticity Can Be Measured in Simple
Hippocampal Circuits

• CaMKII
• Moves existing nearby AMPA receptors into the
  active synapse.
• Increases conductance of Na and K ions in
  membrane-bound receptors.
• These effects all increase the synaptic
  sensitivity to glutamate.

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17 Synaptic Plasticity Can Be Measured in Simple
Hippocampal Circuits

• The activated protein kinases also trigger
  protein synthesis.
• Kinases activate CREB cAMP responsive
  element-binding protein.

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17 Synaptic Plasticity Can Be Measured in Simple
Hippocampal Circuits

• CREB binds to cAMP responsive elements in DNA
  promoter regions.
• CREB changes the transcription rate of genes.
• The regulated genes then produce proteins that
  affect synaptic function and contribute to LTP.

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Figure 17.23 Steps in the Neurochemical Cascade
during the Induction of LTP
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17 Synaptic Plasticity Can Be Measured in Simple
Hippocampal Circuits

• Strong stimulation of a postsynaptic cell
  releases a retrograde messenger that travels
  across the synapse and alters function in the
  presynaptic neuron.
• More glutamate is released and the synapse is
  strengthened.

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17 Synaptic Plasticity Can Be Measured in Simple
Hippocampal Circuits

• There is evidence that LTP may be one part of
  learning and memory formation
• Correlational observations time course of LTP
  is similar to that of memory formation.

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17 Synaptic Plasticity Can Be Measured in Simple
Hippocampal Circuits

• Somatic intervention experiments
  pharmacological treatments that block LTP impair
  learning.
• Behavioral intervention experiments show that
  training an animal in a memory task can induce
  LTP.

102
17 Some Simple Learning Relies on Circuits in
the Mammalian Cerebellum

• Researchers use the eye-blink reflex to study
  neural circuits in mammals.
• An air puff is preceded by an acoustic tone
  conditioned animals will blink when just the tone
  is heard.
• A circuit in the cerebellum is necessary for this
  reflex.

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Figure 17.24 Functioning of the Neural Circuit
for Conditioning of the Eye-Blink Reflex (Part 1)
104
Figure 17.24 Functioning of the Neural Circuit
for Conditioning of the Eye-Blink Reflex (Part 2)
105
Figure 17.24 Functioning of the Neural Circuit
for Conditioning of the Eye-Blink Reflex (Part 3)
106
17 Some Simple Learning Relies on Circuits in
the Mammalian Cerebellum

• Neurons converge in the interpositus nucleus of
  the cerebellum.
• Blocking GABA in this area stops the behavioral
  response.
• The cerebellum is also important in conditioning
  of emotions and cognitive learning, as shown by
  humans with cerebellar damage.

107
17 In the Adult Brain, Newly Born Neurons May
Aid Learning

• Neurogenesis, or birth of new neurons, occurs
  mainly in the dentate gyrus in adult mammals.
• Neurogenesis and neuronal survival can be
  enhanced by exercise, environmental enrichment,
  and memory tasks.
• Reproductive hormones and experience are also an
  influence.

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17 In the Adult Brain, Newly Born Neurons May
Aid Learning

• In some studies, neurogenesis has been implicated
  in hippocampus-dependent learning.
• Conditional knockout mice, with neurogenesis
  turned off in adults, showed impaired spatial
  learning but were otherwise normal.

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Figure 17.25 Neurogenesis in the Dentate Gyrus
110
17 Learning and Memory Change as We Age

• Some causes of memory problems in old age
• Impairments of coding and retrieval less
  cortical activation in some tasks.
• Loss of neurons and/or neural connections some
  parts of the brain lose a larger proportion of
  volume.

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Figure 17.26 Active Brain Regions during
Encoding and Retrieval Tasks in Young and Old
People
112
17 Learning and Memory Change as We Age

• Deterioration of cholinergic pathways - the
  septal complex and the nucleus basalis of Meynert
  (NBM) provide cholinergic input to the
  hippocampus.
• These pathways seem to be involved in Alzheimers
  disease.
• Impaired coding by place cells neurons encode
  less spatial information.

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17 Learning and Memory Change as We Age

• Nootropics are a class of drugs that enhance
  cognitive function.
• Cholinesterase inhibitors result can have a
  positive effect on memory and cognition.
• Ampakines work to improve LTP in the hippocampus.

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17 Learning and Memory Change as We Age

• Lifestyle factors can help reduce cognitive
  decline
• Living in a favorable environment.
• Involvement in enriching activities.
• Having a partner of high cognitive status.