Memory Flashcards
explicit memory (declarative)
storage of facts and epidsodes
further categorized episodic (memory of personal experience) and semantic (words/concepts)
implicit (non declarative)
“motor” learning, changes in skilled behaviors
how does implicit memory affect explicit memories?
implicit memory can affect
salience (how important it was)
valence (emotionality)
accuracy (attention to detail)
important anatomy of the hippocampus
hippocampus
dentate gyrus
subiculum
entorhinal cortex
perirhinal and parahippocampal corticies
object recognition
storage of explicit memory
diffusely distributed in cortex
occurs w/ some laterality
right- spatial
left- object
4 phases of explicit memory
encoding- processes by which new info is attended to and linked to existing info
storage- both the mechanisms and the actual parts of the brain for memory retention
consolidation- processes that endow temporary memories with permanence
retrieval- recall
medial temporal lobe damage impairs which phases of memory?
all 4
working memory location
prefrontal cortex
two components of working memory
verbal and visuospatial info
efficacy of working memory can be modulated by these 2 channels
ACh muscarinic receptors
Dopamine- needs to be at intermediate level
dentate gyrus
engrams- memory traces in the hippocampus
memories of emotionality- fear or reward conditioning
long term potentiation
long lasting, activity dependent increase in synaptic efficacy at an individual synapse
type of plasticity
what are the mechanisms of LTP?
functional changes in-
postsynaptic receptor #
postsynaptic receptor channel function
presynaptic NT release
structural changes-
numbers of postsynaptic spines
size of spine heads
spine stability
CA1 region
send axons that project to the entorhinal cortex and the subiculum
pathway from the entorhinal cortex to hippocampus
perforant pathway
mossy fiber pathway
dentate to CA3
schaffer collaterals
CA3 to CA1
release glutamate neurons, exciting them
shows LTP- following high level of presynaptic activity, epsps are elevated for a log time after
CA2
receive input from lateral entorhinal cortex conveying non spatial info
mice w/o CA2 show deficits in social memory and social behavior
induction vs expression of LTP
induction- biochemical processes that arise from the high level of activity
to induce- need a hihg level activity and release high level of glutamate
postsynaptic AMPA must be depolarized by glutamate
glutamate must activate NMDA receptors
expression- long term changes (structural and function) that underlie synaptic enhancement
AMPA receptors
Na/K, but more Na, low Ca permeability
NMDA receptors
under conditions of low excitation, blocked by Mg
high activity will release Mg, allowing NMDA to come in
NMDA allos Na/K, but also Ca
LTP specificity and associativity
only the synapses that are highly activated and the neighbors are potentiated
neighbor synapses may also receive some potentiation d/t proximity
why is Ca so important for LTP?
activates PKA, PKC and calcium dependent protein kinase II (CAMK-II)
interact w/ ribosomes and mRNA localized to dendritic spines which allow for changes in gene expression:
- insertion of AMPA receptors
- stabilize AMPA receptors in the membrane
- phosphorylation increases AMPA receptor conductance
- actin enlargement of the spine
LTP is a genetic and epigenetic phenomena
ok
long term depression
coordinate pre and post synaptic activity at a lower level than normal.
results in low level of Ca influx through NMDA, which activate phosphateses that promote internalization of receptors and dephosphorylaiton of AMPA receptors
how does stress effect learning?
hippocampal neurons express high levels of glucocorticoid receptors
impairs schaffer collateral LTP and learning and neurogenesis in dentate gyrus
context dependent- only deleterious when rats cant control stresss
when is the most stress sensitive period
juvenility is worse compared to adults
optogenetics to change valence
stimulated dentate gyrus neurons in order to manipulate fear/reward associations in certain memories (change valence)
