Learning and Memory

1. Learning and Memory • Learning = process of acquiring new information. The outcome of learning is… • Memory = persistence of information that can be revealed at at later time.

2. Processes of Learning and Memory • Encoding: processing of new information • Acquisition: sensory registration and analysis • Consolidation: strengthening of representation over time • Storage: creation and maintenance of permanent record • Retrieval: use of stored information

3. Taxonomy of Memory • Sensory: short duration persistence of information • Short-term: medium duration persistence of information • Long-term: long duration persistence of information

4. Properties of Memory • Sensory: short duration persistence of information • High capacity • Iconic: visual, < 1 s duration • Sperling's partial report studies

5. Properties of Memory • Sensory: short duration persistence of information • High capacity • Iconic: visual, < 1 s duration • Echoic: auditory, about 10 s duration • Sams et al. (1993) - mismatch field

6. Properties of Memory • Sensory • Short-term • Limited-capacity • G. Miller - Magic number 7 +/- 2 • Chunking • Maintenance by rehearsal • Loss via decay: Petersen and Petersen (1959)

7. Properties of Memory • Sensory • Short-term • Limited-capacity • Maintenance by rehearsal • Loss via decay • Serial position effect • Primacy: LTM, eliminated by preventing storage (increased pace) • Recency: STM, eliminated by preventing rehearsal (distractor task at end of list)

8. Properties of Memory • Sensory • Short-term • Limited-capacity • Maintenance by rehearsal • Models of STM • "Modal" model (e.g., Atkinson and Schiffrin 1968))

9. Properties of Memory • Sensory • Short-term • Limited-capacity • Maintenance by rehearsal • Models of STM • "Modal" model (e.g., Atkinson and Schiffrin 1968)) • BUT, patients with damage near left supramarginal gryus have impaired digit span and can still form long term memories

10. Properties of Memory • Sensory • Short-term • Limited-capacity • Maintenance by rehearsal • Models of STM • "Modal" model (e.g., Atkinson and Schiffrin 1968)) • Levels of processing (Craik and Lockhart, 1972) • Shallow: superficial, poor LTM • Deep: based on meaning, good LTM

11. Properties of Memory • Sensory • Short-term • Limited-capacity • Maintenance by rehearsal • Models of STM • "Modal" model (e.g., Atkinson and Schiffrin, 1968) • Levels of processing (Craik and Lockhart, 1972) • Working memory (Baddeley, 1995)

12. Properties of Memory • Sensory • Short-term • Limited-capacity • Maintenance by rehearsal • Models of STM • "Modal" model (e.g., Atkinson and Schiffrin, 1968) • Levels of processing (Craik and Lockhart, 1972) • Working memory (Baddeley, 1995) • Damage in LH to Area 40 affects acoustical processing • Damage in LH to Area 44 affects verbal rehearsal • Damage to LH or RH parieto-occipital areas affects visuospatial working memory, but more so in RH

13. Properties of Memory • Sensory • Short-term • Long-term • Virtually unlimited capacity • Loss via interference • Modular

14. Properties of Memory • Long-term • Subdivisions • Declarative: explicit, conscious, personal and world knowledge • Episodic • Semantic • Nondeclarative: implicit, below conscious awareness, skill-based • Procedural • Perceptual representation system • Associative • Nonassociative

15. Patient Studies of Amnesia • Amnesic patients have lost some aspect of memory function after neurosurgery, disease, head injury, etc. • Memory processes (encoding, storage, retrieval) and subdivisions of memory systems (STM/WM, LTM, declarative, nondeclarative) supported by patient data • Region of brain insult key to localization and differentiation of memory functions

16. Patient Studies of Amnesia • Types of amnesia • Illustration following ECT • Anterograde: loss of memory after incident • Retrograde: loss of memory preceding incident

17. Patient Studies of Amnesia • Data supporting differentiation of STM / WM from LTM • Patient EE • Patient HM • Patient RB

18. Patient Studies of Amnesia Lesion location • Patient EE • Removal of tumor in region of left angular gyrus, inferior parietal and posterior-superior temporal cortex

19. Patient Studies of Amnesia Lesion location • Patient EE • Patient HM • Bilateral medial temporal lobectomy to relieve epilepsy

20. Patient Studies of Amnesia Lesion location • Patient EE • Patient HM • Patient RB • Bilateral ischemia localized to hippocampus during surgery

21. Patient Studies of Amnesia Symptomatology • Patient EE • Failure of short-term/working memory (visuospatial sketchpad?) assessed by Token Test • Intact LTM

22. Patient Studies of Amnesia Symptomatology • Patient EE • Patients HM and RB • Anterograde and isolated retrograde amnesia • Normal STM (digit span) • Failure of LTM

23. Patient Studies of Amnesia Summary from Patients EE, HM and RB • Double dissociation of STM/WM and LTM • Patients HM and RB provide evidence that the hippocampus is necessary at encoding stage for consolidation of declarative memories into LTM • Hippocampus is not location for LTM storage (sensory and association neocortex?) • Hippocampus is not involved in LTM retrieval (anterior and lateral temporal cortex?) • BUT hippocampus not the only structure involved in formation of declarative memories

24. Patient Studies of Amnesia Diencephalic Amnesia • Korsakoff's Syndrome • Anterograde and retrograde amnesia similar to HM and RB in alcoholics • Vitamin deficiencies that damage dorsomedial nucleus of thalamus and mammary bodies, but not medial temporal lobe

25. Patient Studies of Amnesia Encoding in Amnesia • Amnesics can learn • Information that can be learned supports distinct memory systems • Often patients like HM can acquire some new semantic, but not episodic,information (loss of source memory)

26. Patient Studies of Amnesia Encoding in Amnesia • Patient KC • Severe head trauma following motorcycle accident • Medial temporal, frontal, parietal and occiptal damage greater in LH than RH • Normal IQ and STM (digit span) • Severe anterograde and retrograde amnesia including loss of all episodic memory • Retained old and could acquire new semantic memories

27. Patient Studies of Amnesia Encoding in Amnesia • Learning nondeclarative information • Procedural learning • Serial reaction time task

28. Patient Studies of Amnesia Encoding in Amnesia • Learning nondeclarative information • Procedural learning • Serial reaction time task • Can be learned by patients like HM and Korsakoff's patients without episodic memory • Learned poorly by patients with basal ganglia disorders (like Parkinson's)

29. Patient Studies of Amnesia Encoding in Amnesia • Learning nondeclarative information • Priming - improvement in identifying or processing a stimulus after observing it • Perceptual representation system • Word fragment completion test

30. Patient Studies of Amnesia Encoding in Amnesia • Learning nondeclarative information • Perceptual representation system • Word fragment completion test • Measure of implicit learning • Performance not affected by depth of processing of list like explicit recognition task • Performance declines across days instead of hours for explicit recognition task • Perceptual phenomenon: performance reduced when list presented auditorially

31. Patient Studies of Amnesia Encoding in Amnesia • Learning nondeclarative information • Perceptual representation system • Word fragment completion test • Impossible figures test

32. Patient Studies of Amnesia Encoding in Amnesia • Learning nondeclarative information • Perceptual representation system • Word fragment completion test • Impossible figures test • Priming occurs for possible figures when deciding whether figure is possible

33. Patient Studies of Amnesia Encoding in Amnesia • Learning nondeclarative information • Perceptual representation system • Double dissociation for PRS • Patient KC • Shows word-priming but no episodic memory • Patient MS • Removal of area 18 & 19 of RH to treat epilepsy • Normal WAIS IQ and memory • No word priming

34. Neuroimaging Studies Declarative Memory • HERA Model: Hemispheric encoding/retrieval asymmetry (Tulving et al., 1994) • Encoding involves LH more than RH • Retrieval involves RH more than LH

35. Neuroimaging Studies Declarative Memory • Criticisms of HERA Model (Miller et al., 2002) • Most studies use word stimuli • Many use poorly controlled stimulus materials • Both hemispheres can encode and retrieve, BUT are specific to material • LH for words • RH for faces • Intra-hemisphere connections given preference over inter-hemisphere connections

36. Neuroimaging Studies Nondeclarative Memory • Procedural memory (Grafton at al., 1995) • Implicit motor learning involves motor cortex, supplementary motor area, putamen, basal ganglia, prefrontal and parietal cortex

37. Neuroimaging Studies Nondeclarative Memory • Procedural memory (Grafton at al., 1995) • Perceptual priming (Schacter et al., 1996) • rCBF reduction in Brodmann area 19