LONG TERM MEMORY. Learning Objective Topics. Retrieval and the Brain. Retrieval Neuroscience of Memory. LTP Brain areas Consolidation Reconsolidation

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1 LONG TERM MEMORY Retrieval and the rain Learning Objective Topics Retrieval Neuroscience of Memory LTP rain areas onsolidation Reconsolidation 1

2 Long-term memory How does info become encoded/stored in LTM? Rehearsal/practice Levels of processing Forming connections or associations Self-reference effect Generation effect Organization of info Imagery How do we retrieve info from LTM? Retrieval cues Encoding specificity / State dependent learning Transfer appropriate processing Retrieval cues Tulving & Pearlstone (1966) Do retrieval cues improve memory? Is forgetting just a retrieval failure? Method Study words (from categories) in random order Test: free recall, cued-recall (provide categories) Ex: Say all the birds, say all the professions, etc. Results Free recall: 40% ued-recall: 75% onclusions YES retrieval cues improve memory! vailability vs. accessibility Tip-of-the-tongue phenomenon (TOT) 2

3 Learning Objective Topics Retrieval Neuroscience of Memory LTP rain areas onsolidation Reconsolidation Episodic Memory Encoding: Hebbian learning" When an axon of ell is near enough to excite a cell and repeatedly or persistently takes part in firing it, some growth processes or metablic change takes place in one or both cells such that s efficiency, as one of the cells firing, is increased - Hebb,

4 Episodic Memory Encoding: Hebbian learning" ells that fire together are wired together re you down with LTP? Long term potentiation ssociative LTP When a weak and a strong input act on a cell at the same time... 4

5 ssociative LTP The weak synapse becomes stronger Rules of ssociative LTP ooperativity LTP may be induced by a single pathway to a synapse OR may be induced by the convergence of many weak stimuli that are active at the same time ssociativity weak inputs are strengthened when co-occurring with stronger inputs Input Specificity There is no spread to other synapses Input specific Only the stimulated synapse shows potentiation 5

6 LTP Synapse level More postsynaptic receptors Dendritic spine What can change during LTP? (How does the synapse get stronger?) Increased release of neurotransmitter Sprouting of new terminal button Smaller, thicker neck of dendritic spine 6

7 re you down with LTP? LTP in the hippocampus may be the building block for long term learning locking LTP prevents learning in rats Learning Objective Topics Retrieval Neuroscience of Memory LTP rain areas onsolidation Reconsolidation 7

8 Movies and memory (amnesia!) ourne Iden<ty (Ma> Damon) Who m I? (Jackie han) The Long Kiss Goodnight (Geena Davis) Memento (Guy Pierce) The Eternal Sunshine of the Spotless Mind 50 First Dates (Drew arrymore) ase studies: mnesia What does evidence from H.M. tell us? What is the medial temporal lobe is necessary for? What is it not necessary for? 8

9 Underside of brain Main structures of medial temporal lobe (MTL) rain areas associated with memory Explicit memory Medial temporal lobe Hippocampus Perirhinal cortex Implicit memory Striatum for procedural skills Neocortex for priming tasks Seman<c memory LeS inferior prefrontal cortex Neocortex - widely distributed Episodic memory Right anterior and dorsolateral prefrontal cortex Medial temporal lobes 9

10 Medial temporal lobe Medial temporal lobe NOT responsible for Implicit memory or procedural memory Not where LTM are stored STM or WM Medial temporal lobe IS responsible for onscious LTM forma<on onsolida<on: Strengthening associa<on Transfer of info from STM to LTM Learning Objective Topics Retrieval Neuroscience of Memory LTP rain areas onsolidation Reconsolidation 10

11 onsolidation Synaptic consolidation rapid Systems consolidation longer restructuring Two theories of how consolidation happens in the brain: Standard Model of onsolidation Event neocortex We process multiple types of information at any given time Squire and Zola 11

12 Standard Model of onsolidation Event Event We process multiple types of information at any given time h1 MTL MTL encodes this information: ensemble of neurons act as a pointer to neocortical neurons represents the attended information. Standard Model of onsolidation Event Event Feature information in neocortex is bound together into an episode (cohesion) h1 h1 We process multiple types of information at any given time MTL encodes this information: ensemble of neurons act as a pointer to neocortical neurons represents the attended information. 12

13 Standard Model of onsolidation Event Event Feature information in neocortex is bound together into an episode (cohesion) We process multiple types of information at any given time h1 MTL encodes this information in an ensemble of neurons that act as a pointer to neocortical neurons representing the attended information. h1 The neocortex is eventually capable of representing the memory without the aid of MTL structures (consolidation) Standard Model How would this predict retrograde amnesia after MTL damage? 13

14 Problem with the Standard Model The hippocampus may be used even for very remote memories. Episodic and semantic memories may be stored in different ways. (Standard model suggests that they are both stored using the same mechanism.) Event Multiple Trace Theory (grees with the Standard Model for this step) neocortex We process multiple types of information at any given time 14

15 Multiple Trace Theory (grees with the Standard Model for this step) Event Event Feature information in neocortex is bound together into an episode (cohesion) h1 h1 We process multiple types of information at any given time MTL encodes this information: ensemble of neurons act as a pointer to neocortical neurons represents the attended information. Multiple Trace Theory of onsolidation h1 Nadel and Moscovitch Each reactivation of the memory trace occurs = different context 15

16 Multiple Trace Theory of onsolidation h1 Reactivation: activate the hippocampus now in a new neuronal context Multiple Trace Theory of onsolidation h1 Reactivation: activate a subset of the feature-traces now in a new environmental context 16

17 Multiple Trace Theory of onsolidation h1 h2 Upon reactivation, a new ensemble of MTL neurons is created multiple, related traces in the hippocampus Multiple Trace Theory of onsolidation h1 h2 Semantic memories = stored separately from the context in which they were learned (episodic memory) 17

18 Multiple Trace Theory of onsolidation Semantic memories become independent of the MTL (represented only in the neocortex) Multiple Trace Theory of onsolidation h1 h2 Episodic memories remain reliant on the MTL pointer to combine all of the sensory attributes experienced. 18

19 Multiple Trace Theory of onsolidation Then why do we get the temporal gradient for retrograde amnesia after MTL damage? h1 h2 The temporal gradient arises because memories with multiple traces (typically those established long ago) are less vulnerable to loss than memories with fewer traces (typically those established more recently) Fill in the prediction of each theory 19

20 Learning Objective Topics Retrieval Neuroscience of Memory LTP rain areas onsolidation Reconsolidation Reconsolidation 41 Nader, Schafe, & Le Doux,

21 Reconsolidation 42 Nader, Schafe, & Le Doux, 2000 Reconsolidation Experiments nsiomycin inhibits protein synthesis Hupbach et al., 2007 human study Propranolol 21