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Hippocampal LTP, learning and memory; synaptic plasticity and…
Hippocampal LTP, learning and memory; synaptic plasticity and neuropsychiatric disorders
what is LTP
role of glutamate receptors
NMDARs - needed for induction of LTP
AMPARs - needed for maintenance of LTP - trafficking of AMPARs (GluA1) to postsynaptic membrane
properties of LTP
rapidly induced
long lasting
co-operativity
input specificity
associativity
occurs in hippocampus - suggested to underlie associative memory
artificially induced LTP
natural LTP
not long lasting
relies on same mechanisms as artificially induced LTP
occurs after learning
types of memory/models of memory
spatial working memory
spatial reference memory - ability to use spatial information to remember where things are - long-term for information across a number of trials
long term habituation
recency dependent memory
associative memory
SOP model
self-generated priming
retrieval-generated priming
short-term habituation
occasion setting
explanations of effects of blocking LTP
SOP model - unable to transfer information from A1 to A2
unable to distinguish overlapping memories with ambiguous cues
STM and LTM are distinct and competing memory processes
LTP is needed for STM, not LTM
role of hippocampus
short term episodic memory (evidence from HM)
spatial memory
object recognition
anxiety
importance of interactions with surrounding brain areas
evaluation of the literature
criticisms
certain methods block LTP throughout the brain - not clear what role of hippocampus is
future research
implications
SCZ - glutamate dysfunction implicated, impaired novelty preference leads to aberrant salience which leads to
effects of blocking LTP in the hippocampus
functions interrupted
spatial working memory (radial maze, visual beacon watermaze)
short-term habituation for objects and spatial information (novelty preference tasks)
recency-dependent object recognition memory (novelty preference object recency task)
sensorimotor side effects - thigamotaxic swimming, unable to stay on platform, slower swimming
greater exploratory behaviour
expression of recency-dependent memory
performance on probe trials
functions left intact
spatial reference memory (standard watermaze)
long-term habituation (can be enhanced)
context-dependent memory (context-dependent novelty preference task)
discrepancies of findings
spatial reference memory
early findings suggest that blocking LTP blocks spatial reference memory (poor performance on standard watermaze)
newer findings with more refined research methods find that spatial reference memory is left intact
effects of hippocampal lesions vs. blocking LTP in the hippocampus
hippocampal lesions tend to impact spatial memory as a whole, but blocking LTP only blocks certain functions
