Neurobiology of Learning and Memory Prof. Stephan Anagnostaras Lecture 6: Multiple Memory Systems: Implicit Memory

Medial temporal lobe; diencephalon Classical conditioning Different types of learning & memory rely on different brain structures Explicit memory Implicit memory Medial temporal lobe; diencephalon Priming (neocortex) Classical conditioning Events (episodic) Procedural memory: skills & habits (basal ganglia) Facts (semantic) Emotional Responses (amygdala) Skeletal musculature (cerebellum) Eyeblink conditioning in rabbit

Squire’s Taxonomy of Memory Implicit memory is a broader term than explicit memory Squire & Zola, PNAS, 1996

Basal Ganglia • Can examine Parkinson’s & early Huntington’s Disease • no apparent amnesia (declarative memory ok) But implicit memory problems in “procedural memory” • Perceptual-Motor Learning • Habits • Skills Separate from motor disorders

Serial Reaction Time (SRT) Task Subjects are not told about the sequence.

SRT Results

Several perceptual motor tasks impaired by basal ganglia damage • Serial Reaction Time • Backwards Reading • Prism adaptation • Mirror drawing • Also more cognitive tasks…

Knowlton, Mangels, & Squire, Science, 1996

Artificial Grammar Learning

Prototype Abstraction

Basal ganglia • Implicit learning deficits in several tasks • Don’t need a motor component • Can be quite “cognitive” • No explicit memory necessary • What about animals?

Packard, Hirsch & White, J Neurosci 1989 McDonald & White, Beh Neurosci 1993 % correct Time spent

Win-Stay Acquisition Trials

Double dissociation paper: Electrolytic lesions on win-stay Packard, Hirsh & White, J Neurosci, 1989

Win-Shift Training Training Phase Delay Testing Phase Baited

Double dissociation paper: Electrolytic Lesions on win-shift Packard, Hirsh & White, J Neurosci, 1989

Triple D Histology (HPC + DLC) McDonald & White, Behav Neurosci, 1993

Triple D: Neurotoxic DLC lesions impair win-stay learning McDonald & White, Behav Neurosci, 1993

Triple D: Neurotoxic DLC lesions spare win-shift learning McDonald & White, Behav Neurosci, 1993

Triple D: Neurotoxic HPC lesions impair win-shift learning McDonald & White, Behav Neurosci, 1993

Triple D: Neurotoxic BLA lesions impair conditioned cue preference McDonald & White, Behav Neurosci, 1993

Proposed characteristics of habit learning Squire, 1992: • Knowledge expressed through performance, rather than recollection • Associations acquired across many trials • Less flexible (less transferable) than declarative learning Salmon & Butters, 1995: “Habit learning refers to the formation of simple associations in which a neutral stimulus comes to elicit a certain motor response as a function of repeated reinforcement.” Mishkin et al., 1984: Product of processing is “not cognitive information, but a non-cognitive simulus-response (S-R) bond…what is stored is not objects, emotions…but the changing probability that a given stimulus will evoke a specific response due to the reinforcement contingencies at that time”

Sage & Knowlton, Beh Neurosci, 2000 US Devaluation of Win-Stay (Testing the hypotheses) Protocol: Train US devaluation Test • If performance does not involve representation of US, the CR should remain intact (e.g., accurate, fast) on test. This would be consistent with an S-R view. • If performance mediated by representation of US, then recall of devalued US should change the CR (e.g., inaccurate, slow) on test

Devaluation following win-stay acquisition

Win-stay late timepoint post-CTA trials xx

Post-CTA win-stay accuracy summary 2, 9, or 22 days

Post-CTA win-stay latency summary * * * = significant difference

Contextual Cuing Task (Chun & Phelps, Nat Neurosci, 1999) Easy Version Difficult Version

Contextual Cuing Task (Chun & Phelps, Nat Neurosci,1999) Amnesics 2 anoxic (1 conf hipp) 2 encephalitic (2 conf hipp) Implicit Learning Deficit in Amnesia !

Memory systems in Implicit Memory • Not all implicit memory is independent of the hippocampus • Not all implicit memory depends on the basal ganglia, e.g., emotional learning, priming, certain motor responses • Cortical systems (e.g., priming) • Amygdala (fear conditioning) • Cerebellum (eyeblink conditioning) …etc