Limbic System

Question 1

Describe declarative memory

Answer 1

ability to recollect events or facts with specific temporal/spatial context + sematic knowledge (general knowledge of world + new words)

ex = name president in 2000, where you were yesterday

Question 2

Describe procedural memory

Answer 2

ability to learn new motor skill

learned skill remain if damage declarative memory but act of learning not retained
ex = ride bike, trace shape

Question 3

what lesions would impair declarative memory

Answer 3

hippocampal lesion (can’t consolidate memory and transfer storage to cerebral cortex)

Question 4

what lesions would impair procedural memory

Answer 4

cerebellum, basal ganglia, frontal cortex lesion

Question 5

Understand short term vs working vs long term memory

Answer 5

based on time
1) short term = fraction of sec to second
in sensory cortex
ex = grasp obj to hold on to

2) working = sec to min
in frontal lobe
ex = what ingredient in recipe

3) long-term = day to year
in hippocampus to cortex
ex = remember face

Question 6

what kind of memory affected by lesions to frontal cortex

Answer 6

working memory

Question 7

what is experimental evidence showing neocortex is site for long term memory storage

Answer 7

lesion + fMRI show neocortex = long term memory storage

fMRI show activity in cortex when shown faces (long term declarative)

facial recog stored in inferotemporal cortex

Question 8

Reason for memory deficits by HM

Answer 8

1) HM = remove hippocampus, entorhinal complex + amygdala bilaterally (can’t process memory to store in cortex)
2) developed anterograde amnesia limited to declarative memory
3) couldn’t recall what done yesterday but could still learn new things since procedural intact

Question 9

define associative memory

Answer 9

associative memory = learning to assoc several cues with particular fact or obj in memory

ex = play more charades, use less cues for recall

Question 10

How does LTP account for associative memory

Answer 10

LTP strengthen assoc memory by decr # of cues to make association

Question 11

anatomy of hippocampus

1) what are two layers
2) what is ammon’s horn made of

3) mossy fibers project where
4) schaeffer collaterals project where

Answer 11

1) 2 layers = dentate + Ammon’s horn
2) ammon’s horn = CA3 + CA1 neuorns
3) mossy fibers project from dentate gyrus –> CA3 neurons
4) schaeffer collaterals = CA3 neurons –> CA1 neurons

Question 12

describe input and output from hippocampus

Answer 12

input = entorhinal cortex –> perforate path –> hippocampus

output = CA1 and CA3 neurons –> fornix

Question 13

LTP
1) which cells undergo LTP and what do they require stim by

2) what happens when stim occurs

Answer 13

1) CA1 or CA3 cells and require stim by Schaeffer collat or mossy fibers
2) when stim vigorously and repetitively, synaptic strengthening occurs –> need fewer input for depol due to AMPA and NMDA

Question 14

Mechanism of coincidence detection triggering LTP

Answer 14

1) depol + glutamate activate NMDA
2) calcium enter –> stim calmodulin
3) calmodulin –> activ CAMKII which phosphorylate itself (long lasting for days)
4) insert more AMPA in cell membrane and become phosphorylated even when Ca2+ decr so more sensitive to glutamate
5) CA1 or CA3 cell now more sensitive to activ and need fewer assoc

Question 15

under what circumstances do hippocampal synapses undergo LTP

Answer 15

only synapses stim during tetanus

only occurs when tetanic burst large enough to cause depol in postsynap neuron (only CA1 or CA3)

(basically need enough depol + glutamate)

Question 16

molecular basis for LTP

Answer 16

1) NMDA receptor on CA1 or CA3 activ by glut and cell depol
2) Ca2+ influx
3) activate calmodulin
4) activation of CAMKII
5) incr insertion and sensitivity of AMPA receptors –> LTP

coincidence detection

Question 17

how could synapse formation and adult neurogenesis be involved in learning and memory?

Answer 17

1) synapses = not static and undergoes formation/retraction

common in somatosensory cortex

2) adult neurogenesis in olfactory bulb, hippocampus, cerebellum
(olfaction, declarative, procedural learning respectively)

3) songbirds learn to sing = new neurons born in brain

Question 18

understand the amyloid hypothesis of alzheimer’s

Answer 18

APP cleaved by alpha and beta secretes normally

in AD, APP cleaved by beta, gamma secretase –> Abeta amyloid

Question 19

what are implications of amyloid hypothesis for developing new treatments?

Answer 19

mice with amyloid can’t maintain LTP for memory in hippocampus

therapies to decr Abeta peptide could help AD patients
(drugs to inhib gamma and/or beta secretases)

Question 20

role of limbic system and amygdala in emotion

Answer 20

amygdala = associative learning for painful harmful stim such as aversive food, loud sound, or mech stim

either innate, assoc learning, or fear condition

Question 21

how does associative learning occur

Answer 21

2 stim evoked at same time –> coincidence detection (pavlov dog)

or assoc stim occur at diff times

Question 22

mechanism of conditioned fear aversion

Answer 22

assoc learning without simultaneous presentation of assoc stim

1) initial exposure to food –> release ACh from basal forebrain throughout brain
2) ACh bind MRs in insular cortex (taste cortex)
3) causes phosphorylation of NMDA in insular –> sensitize to stim from amygdala (lasts 30 min)
4) amygdala then later stim by “feels of malaise” from vagus nerve
5) now simult input at insular from amygdala + vagus nerve = associate food with malaise

Question 23

ex of conditioned fear aversion

Answer 23

1) pt receive chemo given food, later become sick and then assoc that food with ill

initial stim = food
present prior to assoc stim = feeling ill

but condition still occur