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Learning & Memory (AMNESIA:
THE CASE OF H.M. (IMPACT OF H.M (First…
Learning & Memory
AMNESIA:
THE CASE OF H.M.
Severe, intractable epilepsy
bilateral foci in medial temporal lobes
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IMPACT OF H.M
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STM v. LTM
consolidation: period after initial learning when memory is unstable
reproduced in many animal models
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Long-Term Memory
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Implicit:
Priming: neocortex
Procedural (skills, habits): striatum
Emotional: amygdala
Motor learning: cerebellum
Nonassociative learning (e.g. habituation):
reflex pathways
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SYNAPTIC
MECHANISMS
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NMDA RECEPTORS
In many brain areas, LTP depends on NMDA receptors
During induction of LTP, NMDA receptor channel opens, permitting influx of Ca2+ ions
Ca2+ ions trigger multiple molecular cascades, leading to
long-term changes in synaptic strengths
Ligand- and voltage-gated
Activated by simultaneous activity in pre- and postsynaptic cells:
Presynaptic activity: Provides ligand (glutamate)
Postsynaptic activity: Provides voltage (depolarization)
synaptic connections between cells
strengthened if cells activated simultaneously
(“coincidence detector”)
ANIMAL MODELS
OBJECT RECOGNITION
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Impairment after damage to medial temporal lobe:
hippocampus, amygdala, and rhinal cortex
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PLACE CELLS
Cells that produce high frequency of nerve impulses when
animal is situated in a particular place in hippocampus
