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Learning & Memory (Evidence (Relevance to humans (Tetanic stimulation
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Learning & Memory
Evidence
Morris Water Maze
after learning rat finds platform very quickly
lesion/remove hippocampus
memory capability lost
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trainig (acuisition)
consoldation
testing (recall)
block protein synthesis at consolodation stage no memory
CREB transcription factor
Relevance to humans
Tetanic stimulation
Theta rhythms
associated with synchronisation
hippocampal theta associated with:
running, swimming, headmovements, etc.
stimulation at peak of theta activity - LTP
stiulation at trough - LTD
disruption of theta waves (cholinergic drugs - scopolamine)
causes similar effects to hippocampal lesions
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LTP
Hippocampus
Bliss & Lomo (1973) found that one high frequency stimulation (HFS) lasted hours in hippocampus.
Several HFS lasted days/months (temporal)
one stimulation now activated where it didn't before
LTP - respond to same stimulus more sensitively
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Temporal
e.g. HFS
LTP on single pathway
Associative
simultaneous stim of both strong & weak pathway
LTP at both pathways
specific
LTP at one synapse not propogated to others
need activity and depolarisation
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Learning
NMDA
At the synapse
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late phase LTP
protein synthesis required
CREB activated by neuron activation
in cell body.
switches on new genes
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Early vs Late phase
Early phase
last minutes or hours
explained by Ca2+ through NMDA receptor
new AMPA + enhanced AMPA
late phase
lasts hours, days, months, years...
new protein synthesis (CREB)
morphological changes or new synapses
Ca2+ activated
protein synthesis postsynaptic
LTP in amygdala
coincidental firing in the LA (lateral amygdala)
spatial summation
associative learning
output to central nucleus of amygdala (CE)
Glutamate at receptors
AMPA fluxes Na+ into postsynaptic neuron
once depolarised to -30mv voltage dependent NMDA activates
MG2+ leaves pore