Memory the Medial Temporal Lobe Lesson 22 Memory
Memory & the Medial Temporal Lobe Lesson 22
Memory Storage of information l perceptions l learning l personality n Information processing approach l RAM vs. hard drive n Multiple memory stores l different characteristics n Clive Wearing ~ n
Multiple Memories Sensory memory l capacity: large; sensory receptors l duration: < 1 sec. n Short-term memory (STM) l capacity: 7 ± 2 chunks l duration: < 1 min. l maintenance: rehearsal ~ n
Multiple Memories Long-term memory (LTM) l capacity: functionally unlimited l duration: minutes - years n Working memory l intermediate to STM & LTM l information needed longer than 1 min, but not permanent ~ n
A Model of Memory rehearsal stimuli Sensory Memory attention transfer STM LTM retrieval forgetting
Subdivisions of LTM 1. Declarative - Explicit n Episodic: l autobiographical l time-tagged, automatic n Semantic: l generic l not time-tagged, effortful ~
Subdivisions of LTM 2. Procedural – Implicit l non-declarative, unconscious n Motor learning n Nonassociative Learning l modulation of reflexes n Associative Learning l Classical & Operant Conditioning ~
Neural Mechanism of STM Donald Hebb n Change in neural activity l not structural l temporary n Reverberatory Circuits l cortical loops of activity l activity persists for short period of time ~ n
Reverberating loops n Maintains neural activity for a period
Neural Mechanism of LTM relatively permanent l structural change required n Hebbian Synapse l use strengthens synaptic efficiency l requires simultaneous activity l pre- and postsynaptic neurons l Long-term potentiation (LTP) ~ n
Where are memories stored? Engram l physical change representing learning and memory n Lashley l Mass Action & Equipotentiality n Classical Conditioning: Eye-blink l lateral interpositus nucleus of cerebellum n Memories stored locally l in different parts of brain ~ n
H. M. Greatest contribution to study of memory l can’t remember any of it l similar to Clive Wearing n Bilateral medial temporal lobectomy l to control seizures l hippocampus (HC) ~ n
Hippocampus Mid-sagittal View
Spared some memory Personality n Intelligence n LTM n Verbal STM memory OK n Motor skills n
Memory Deficits Some retrograde amnesia l but many old memories intact n Severe anterograde amnesia l unable to form new memories ~ n Trauma Retrograde Anterograde time
Evidence of deficits Digit Span + 1 n Block tapping memory span n Delayed-matching-to-sample l verbal OK - rehearsal l nonverbal impaired – ellipses ~ n
Evidence of Spared Abilities Performance improved with practice l Procedural memory l but no conscious memory of it n Mirror Drawing n Tower of Hanoi ~ n
Conclusions: Role of Hippocampus Removal of HC deficits n Memory Storage? l STM not in HC l LTM not in HC transfers info STM LTM? l Declarative memories: YES l Procedural: NO n H. M. anterograde amnesia for declarative memories ~ n
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