Memory and Amnesias Flashcards
contrast declarative (explicit) vs procedural (implicit) memory
- declarative (explicit)
- facts: what is the capital of Georgia?
- events
- procedural (implicit)
- skills/habits
- priming
- conditioning
contrast retrograde vs anterograde amnesia
describe infantile, transient global and dissociative amnesias
- infantile amnesia: early childhood events cannot be recalled
-
transient global amnesia: occurs typically in older men, recent events and information can only be remembered for a few minutes; normally all other fxns are not impaired
- possible causes: TIA, basilar artery migraine, physical or psychological stress
- dissociative amnesia: psychological reaction (witness of a severe accident or crime)
describe Wernicke-Korsakoff amnesia (diencephalic amnesia)
- caused by thiamine deficiency in patients with alcohol abuse; symptoms include confusion, confabulation and severe memory impairment
contrast diencephalic and bilateral mesial temporal amnesias
describe the hippocampal pathway
- neurons in the entorhinal cortex relay excitatory signals to cells in the dentate gyrus which in turn excite CA3 cells in the hippocampus
- the CA3 cells have collateral axons that make excitatory synapses with CA1 neurons in the hippocampus
- the CA1 neurons pass on the excitatory message to cells in the subiculum which, in turn, relay signals back to the entorhinal cortex
- impulses passing through this loop induce synaptic plasticity at synapses on cells of the dentate gyrus, hippocampus and the subiculum
draw out the hippocampal pathway
describe the standard consolidation theory
- the hippocampus is the conductor of the memory engram symphony
- the hippocampus and surrounding regions come on-line to bind sensory tracings from various cortical regions (via entorhinal) into a cohesive memory engram
- these symphonies are rehearsed often enough (via diencephalic system) until the band can play on its own, without the hippocampus
- these hippocampal independent symphonies (i.e. long term memories) are robust to hippocampal damage but will not form in the absence of sober (i.e. functionally intact) conductor
describe the multiple trace model
- the standard consolidation model of memory suggests that memories eventually become hippocampal independent
- multiple tract models of memory suggest that memory recall always activates the hippocampus to some extent
- memory retrieval brings an engram “online” to incorporate new information and form “multiple traces”
- reconsolidation: reactivation of memory traces renders them labille/malleable via involvement of hippocampal system
describe long term potentiation (LTP) in the hippocampus
- when CA1 neurons are excited by a high frequency train of impulses along the Schaffer collateral axons of a CA3 neuron the excitatory synapse undergoes a large long-lasting increase in synaptic efficiency called LTP
- the synapses showing this potentiation are glutamatergic synapses on dendritic spines in the CA1 neuron
describe graphs of LTP in the hippocampus
describe increased synpatic strength/efficiency
- an increase in AMPA channel conductance (early effect)
- an increase in the number of AMPA receptors (early effect)
- an increase in the number of synapses involving formation of new dendritic spines and increased synaptic boutons (late effect)
describe long term depression (LTD) in the hippocampus
- when a CA1 neuron is excited by an impulse train at low freq. train of impulses passing along the Schaffer collateral axons of a CA3 neuron, the excitatory synapse undergoes a large persistent fall in synaptic efficiency
- thus, the same synapses that show LTP when stimulated intensively can also show LTD when stimulated weakly by CA3 neurons
describe graphs of LTD in the hippocampus
the activation of ____ receptors is a prerequisite for both, LTD and LTP–the crucial difference is the different _____ that are produced by intense and weak stimulation of the axons of the ____ neurons
the activation of NMDA receptors is a prerequisite for both, LTD and LTP–the crucial difference is the different rises in intracellular [Ca2+] that are produced by intense and weak stimulation of the axons of the CA3 neurons
describe the role of [Ca2+] in LTP vs LTD
