learning & memory Flashcards
What was the hypothesis of the mechanism of memroy?
measurable changes in synaptic transmission occur as a task is repeated
synaptic facilitation
increased efficacy of synaptic transmission will enhance memory formation
sensitization is a form of synpatic facilitation
facilitation of a synaptic pathway
-primitive form of learning and memory
synaptic inhibtion
suppression of memory formation
habituation is a form of synaptic inhibition
primitive form of memory suppression “learning to ignore”
An aplysia is an invertebrate whcih exhbits primitive forms of memory. How does he exhibit habituation?
decreasesd behavoprial response with repeated stimulation– when poking its tail it willeventually stop withdrawling
An aplysia is an invertebrate whcih exhbits primitive forms of memory. How does he exhibit sensitization?
increased response persisting for days to weeks if a facilitator path activated– if the slug is tazed
Habituation in aplysia may be due to what?
decrease activity of VG Ca2+ channel (adaption) and reduced transmitter release
how does sensitization in aplysia work?
- Facilitator releases serotonin onto sensory neuron terminal
- Adenylyl cyclase activation increases cAMP
- cAMP activation of PKA inhibits S-K+ channels (presumed phosphorylation)
- Sensory neuron terminal depolarized and sensitized
- Transmitter release increased
Key structures of memory
Hypothalamus Hippocampus Amygdaloid body Cingulate gyrus Mamillary body Anterior nucleus Paraolfactory area
Key tracts of the human memory
Fornix- (body and column)
Mamillothalamic Tract
Stria terminalis
how does short term memory occur?
repeated activation of a memory trace circuit could facilitate synpatic transmission for a brief period (reverberating circuit)
intermediate long-term memory occurs for minutes, hours, dyas resulting form what?
a temporary chemical or physical change that persists
long-term memory persists for years; what does it involve?
involves protein synthesis and sturctural synaptic changes
Working memory definition
prefrontal area encodes many bits of information simultaneously and recalls information instantly as needed for subsequent thoughts
consolidation
conversion from short-term to long-term memory
What is the cAMP hypothesis of consolidation?
repeated sensitization increasing cAMP eventually activates CREB and triggers new protein synthesis
declarative (semantic) memory
recal of facts and details
limbic circuits
What are the 2 parallel memory circuits of the limbic system?
anteriror nucleus circuit and the dorsal medial circuit
What is the circuit for the declarative memory?
hippocampus–> mamillary body–> anteriror nucleus to cingulate gyrus
What is the circuit for emotional memory?
amygdala–> dorsal medial nucleus and septal area–> prefrontal/limbic associaton areas and reward center
Where does emotional memory really begin at?
paraolfactory but it has direct input to the amygdala
matches prior experience with current circumstances to evoke an appropriate behavioral repsonse
amygdala
What input is critical for decision-making?
olfactory
a model for learning and memory seen in rat hippocampus
hippocampal long-temr potentiation (LTP)
What is the tri-synaptic pathway of LTP?
Perforant path- cortical input to Granule cells
Mossy fiber path- Granule cell axons to CA3 neurons
Schaffer collateral path- CA3 neurons to CA1 neurons
CA1 neurons project to the mamillary body via fornix. What is this the basis for?
‘reverberating circuit’ amd memory formation
Pathway 1 & 2 of LTP control..
stimulation of CA3 which evokes EPSP
What causes EPSP enhancement?
NMDA receptor
NMDA receptor
glutamate receptor subtype highly expressed on CA1 neurons
CA1 neurons express another glutamate recpetor called _____ which is not permeable to ____.
AMPA receptor
not permeable to Ca2+
Non-LTP (pathway 2)
glutamate release form CA3 neurons activates AMPA receptors on CA1 neurons
LTP (pathway 1) tetanic stimualtion removes magnesium block whihc allows ___.
calcium to enter CA1 neuron
Once the calcium enters the CA1, what occurs?
nitric oxide synthesis
which may activate presynaptic guanylate cyclase, inc in cGMP causes enhanced glutamate release
feedback on postsynaptic NMDA receptors to increase responsiveness
anterograde amnesia
inability to form new memories after a critical event
retrograde amnesia
inability to access stored memories prior to a critical event
Possible causes of retrograde amnesia
stroke, infection, trauma, electroshock therapy
Possible causes of anterograde amnesia
alzheimer;s, temporal lobectomy, Wernicke-Korsakoff, limbic encephalitis
clinical features of alzheimer’s
Anterograde amnesia occurs first; retrograde amnesia much later
Language deterioration
Motor and sensory functions spared until late stage
Sporadic AD ~85% of cases etiology is not known but it is believed to be because of what hypothesis?
multiple hit hypothesis
alpha beta 42 peptide
beleived to be amix of small mutaitons
APP695 mutants lack what?
alpha secretase cleavage site
What is the hallmark of Alzheimer’s disease?
alpha beta 42 accumulation in synaptic cleft of hippocampal neurons froms amyloid plaques
Wernicke-Korsakoff Syndrome
thiamine (vit B1) deficiency causes memory deficits and amnestic confabulation
Limbic Encephalitis can be caused by…
infection or autoimmune
