Wednesday May 3

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Wednesday May 3 Review session today after
class W-2-126 Final assigned for Tues AM,
May 16 trying to change to Monday
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• How does the increased Calcium lead to LTP?
• the presence of Ca appears to activate enzymes
  (calmodulins)
• CaMKII (alpha calcium calmodulin dependent
  protein kinase II) appears critical
• Inhibit CaMKII and LTP does not occur
• CaMKII changes the circuitry in such a way that
  the next time the presynaptic neurons fire and
  release GLU, the postsynaptic neurons respond at
  a lower threshold for firing

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• How does the circuit become easier to activate
  and remain that way?
• the threshold of AMPA receptors on the
  postsynaptic neuron becomes more sensitive, AMPAs
  fire more easily and unblock Mg, then NMDAs
  cause postsynaptic neuron to fire
• more receptors are also built
• some presynaptic changes occur perhaps leading
  to release of more Glutamate
• this lasts for seconds to minutes and is
  reinforced every time the circuit fires in the
  future

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Neurons throughout brain show changes with
experience. LTP mechanism appears to be active in
many different brain areas, specifics vary. Other
important neurotransmitters and receptor types
GABA, acetylcholine, and others
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3. Long term memory storage requires protein
synthesis - proteins are used for changes in
receptors on postsynaptic neuron to occur -
proteins are necessary for dendritic changes and
increased points of contact from presynaptic
neuron to postsynaptic neurons to occur -
Protein synthesis is activated, in part, by
CaMKII and also by cAMP Protein synthesis
changes LTP in hippocampus into stored forms in
hippocampal-cortical circuits, then just
cortical residence.
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• Relevant proteins for LTM are formed when
  certain proteins bind with cAMP - these are
  called CREB (cAMP responsive element binding)
  proteins
• Manipulations
• 1. Inhibit protein synthesis during period after
  learning, LTM does not take place
• But, inhibit protein synthesis, STM occurs
  normally not affected
• Temporal, anatomical, and neurochemical
  differences across stages of memory.

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Three important questions 1. What are the
categories of long term memory? 2. What
structures help individual short term memory
circuits become long term memories? A.
consolidation for organized storage occurs in the
medial temporal lobes B. The mechanisms for
making the memories involve LTP 3. Where are
long term memories stored?
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• Where are long term memories stored?
• Appear to be stored in cortical circuits that
  are active at time of information processing or
  event occurrence
• Circuits from hippocampus to cortical sites are
  relevant for retrieval of newer LTMs
• Remote memories Hippocampus remains necessary
  for retrieval of spatial location memories.
• Only cortex is minimally necessary for episodic
  and semantic memories but large debate
  surrounding need for hippocampal involvement to
  get vivid, detailed memories.
• Different types of semantic memories stored in
  different cortical locations. Damage to specific
  cortical regions causes specific types of memory
  loss.
• Different frontal cortical areas associated with
  naming objects vs animals vs people.

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Laterality
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• Hemispheric Differences in Cognitive Processing
• dominance of control of function by left versus
  right hemisphere
• originally studied (1960s) through Split-Brain
  preparation - individuals with corpus callossum
  cut (Roger Sperry - Nobel prize - 1981)
• Corpus callossum - major connection between 2
  hemispheres
• earliest work involved presentation of visual
  stimuli

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Red (left) and blue (right) designate the
hemifields of each eye. Note straight path and
crossing over. L to left right to right.
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Path from Eye to Brain Left and Right Optic
Nerves -- Optic chiasm -- Optic tract At optic
chiasm, half of each optic nerve from each eye,
crosses over to other side of brain. By
delivering info. selectively to right vs left
visual halffield, can send info. to left vs right
visual cortex. In split brain, info. stays where
first received -can selectively stimulate left or
right cortex (hemisphere).
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• Split Brain
• corpus callossum is cut!
• optic chiasm is intact!
• Deliver info selectively to left hemisphere via
  left half-field - it cannot then cross over.
  Info sent to left hemisphere only.
• Or deliver selectively to right halffield and to
  right hemisphere.
• Remember! stilumi are delivered to a slected
  halffield of each eye not to the right vs left
  eye!!

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Visual field for each eye has two halves Left
visual half field (left side of left and right
eye) - sends information to the left
hemisphere Right visual half field (right side of
left and right eye) - sends information to the
right hemisphere In normal brain, info. then
crosses over to other side via corpus
callossum. In split brain, info. cannot
cross. Thus, info can be selectively sent to one
hemisphere.
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Red (left) and blue (right) designate the
hemifields of each eye. Note straight path and
crossing over. L to left right to right.
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(No Transcript)
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Delivery of info to right visual half field of
left eye right hemisphere Sometimes done with
right eye blocked as shown.
Info crosses over
Cannot cross over RH only
Person fixates on red X
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Results of split brain research 1. Structures in
LH allow naming of objects RH cannot. 2. RH
structures can show identification by pointing
(or drawing) with left hand, but not by naming
3. LH structures can also point using
contralateral (opposite side) hand. 4. When
different info presented to each hemisphere, will
name what the left hemisphere saw, but draw what
the right hemisphere saw.
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Experiments with the olfactory system -
smell Anatomical organization Left nostril -
sends odor info to left hemisphere Right nostril
- sends odor info to right hemisphere Right
hemisphere cant name the odor, but it can direct
the left hand to select the object smelled.
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Rose smell delivered via right nostril to the
right hemisphere. Subject cant name it but can
choose a rose with left hand.
X X X
This line ? from brain to hand
actually goes through brainstem not across
corpus callossum CC is cut)
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Other research on intact brain examines
laterality Auditory studies - can selectively
deliver to right or left hemisphere Anatomical
organization Info to left ear right
hemisphere first. In normal brain, it then
crosses back over to left hemisphere where sound
can then be described thru speech. Takes
longer. Info to right ear ?left hemisphere.
Already in the correct location (LH) to allow
describing - can do so faster.
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Auditory paths in normal brain
(stimuli occur at the same time)

MA Goes to RH 1st
PA Goes to LH 1st
Subject says PA
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• Results of other research
• LH typically has speech center
• LH better at language processing
• 2. LH better at language-related sounds
• 3. LH better at verbal memory
• 4. LH better at math and science
• 5. LH better at logic and analytic thought.
• Better more accurate and faster on tasks.

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Results of other research 1. RH better at visual
memory 2. RH better for environmental sounds 3.
RH better for face perception and emotion
recognition 4. RH superior for visuospatial
skills Puzzles Sense of
direction Geometry Mental
rotation of shapes