Memory and Amnesia

1. Memory and Amnesia Nathan Spreng Cognitive Neuroscience: PSY393 August 2, 2005

2. Amnesia at the movies

3. Remember Sammy Jankis?

4. Memory Lecture Summary • Memory • Process and Definitions • Systems • Medial Temporal Lobe & Classic Amnesia • Encoding & Retrieval • Case studies • Frontal Lobes • Working Memory & DLPFC • Working with Memory • Case study • Autobiographical Memory

5. Memory is... • A group of mechanisms or processes by which experience shapes us, changing our brain and behaviour • The product of learning

6. Memory involves... • Acquisition • Retention • Ability to retrieve • information • personal experiences • procedures (skills and habits).

7. Memory enables... • Adaptation to the environment • Improvement of our interactions with the outside world • Intergenerational transfer of knowledge

8. Short and Long Term Memory • Memory can be divided into • Time (seconds to minutes to years) • Contents (7 plus minus 2) • Systems by type of information

9. Memory processes 1. Registration 2. Encoding 3. Consolidation 4. Storage 5. Retrieval 6. Re-encoding Sensory perception in sensory brain areas Initial processing (association with previous information) - Trace Deeper processing: Engram formation Stable representation in central nervous system Reproduction of previously stored information: Recollection Re-encoding through retrieval; initial trace (engram) changes

10. Memory Systems

11. Memory Systems • Implicit Memory: Memory without awareness • Skills, priming, etc (spared in amnesia) • Explicit Memory/Declarative Memory • Memory accompanied by an awareness of recollection. May be “declared” or verbally reported

12. Amnesia • Definition: “An abnormal mental state in which memory and learning are effected out of all proportion to other cognitive functions in an otherwise alert and responsive patient” • Kopelman (2002) • Memory can be compromised in isolation from other cognitive abilities • Amnesia is selective, effecting certain capacities, showing that there are many systems of memory

13. Temporal Extent of Amnesia • Anterograde amnesia • Deficit in new learning • Inability to form new memories AFTER time of injury • Retrograde amnesia • impairment of memory of information PRIOR to onset of amnesia • temporal gradient, effecting recent > remote

14. Temporal Extent of Amnesia • Ribot’s Law (1882): “The progression of the destruction of memory follows a logical order. It begins with the most recent recollections, being rarely repeated, and having no permanent associations” • Greater compromise of recent memory over remote

15. Temporal Extent of Amnesia

16. The case of H.M. • HM - surgery for intractable epilepsy. • Resection of hippocampus, parahippocampal gyrus, amygdala & uncus. • HM could not form new memories (anterograde amnesia). • Retrograde amnesia (11 years) • Right: HM vs. 66-yr old Control Anterior Posterior (Corkin et al., 1997)

17. Etiology of Amnesia • Korsakoff’s syndrome (Jimmy) • Herpes encephalitis (Clive) • Severe hypoxia • Vascular disorders • Head Injury (K.C.) • Dementia (J.S.) • Transient global amnesia (fugue state)

18. Amnesia • Inability to form new long term memories • Assessed with • Free recall (no info) • Cued recall (starting with “c”) • Recognition (target and lures used) • Savings in relearning (also impaired in amnesia)

19. Memory Systems Impaired Spared

20. Implicit Memory • “Memory without awareness” • Spared in classical amnesia • Priming – Primary Sensory Cortex • Procedural Memory - Striate

21. Implicit Memory • Gollin Incomplete Pictures task • Repetition Priming • Bias to previous exposure

22. Implicit Memory • Eye movements to assess implicit memory • Top: Initial exposure, eye movements over 3 items • Bottom: 2nd exposure, eye movements over where one item would be

23. Implicit Memory • Procedural Memory • Improvement in performance without recollection of the material • Spared in amnesia Mirror Reading Task

24. Declarative Memory • Semantic Memory: “Knowing” • Knowledge of words and their meanings, objects, concepts and facts. • Episodic Memory: “Remembering” • Re-experiencing of an event that occurred in the past including time and place of original encoding episode…mental time travel.

25. K.C. normal The case of K.C. • TBI • Bilateral hippocampus & frontal lobe damage • Severe RA and AA • No episodic memory • Intact semantic memory

27. Memory Circuit (Mayes, 2000)

28. Main memory structures & connections MTL Diencephalon

29. 1. Perirhinal cortex Mamillary bodies 2. Entorhinal cortex 3.Parahippocampalcortex Hippocampal formation Subiculum CA1 CA2 CA3 Dentate gyrus 1-3 = Parahippocampus Structures of the Medial Temporal Lobe

30. Medial Temporal Lobe • Hippocampus as Convergence zone • Memories are not stored within the hippocampus • Hippocampus acts as an “indexor” and lays trace of memories. • Memories are stored in sensory cortex • Hippocampus has access to all sensory information • Relational Memory

31. Medial Temporal Lobe • Morris Water Maze • Hippocampal lesions • Deficits in learning and remembering spatial relations

32. Hippocampal Lesions: Material specific memory disorder Unilateral Left: verbal impairment Right: nonverbal impairment Bilateral - Global impairment fMRI Hippocampus: Material dependent activity at encoding Verbal - Left Nonverbal - Right Medial Temporal Lobe

33. Medial Temporal Lobe • Hippocampal activity predicts successful recall • During encoding • During retrieval (Nyberg, et al., 1996) • “Subsequent Memory Effect”

34. Medial Temporal Lobe • While memories are young, they depend upon an intact hippocampus • Are old episodic memories independent hippocampus once consolidated?

35. Medial Temporal Lobe • fMRI: Robustness of hippocampal activity during retrieval related to vividness of memory, not age (Gilboa, 2003) • H.M. possesses some remote memories. • Are they episodic? Depends on measure • lack episodic content, “semanticized” (Steinvorth & Corkin, submitted)

36. Medial Temporal Lobe • How does the hippocampus bind information? • LTP • Hebb’s Law • Connectivity (Rolls, 2000)

37. Same brain regions activated for perception and retrieval • Regions • fusiform gyrus (a) • superior temporal gyri (d) • Retrieval of pictures and sounds, respectively (2004) Proc. Natl. Acad. Sci. USA 101, 5181

38. MTL & Emotion • Emotionality enhances memory performance • Mediated by the Basolateral limbic circuit • Parahippocampus and perirhinal cortex connect with the amygdala • Orbitofrontal cortex involved in processing salience at encoding • Emotion enhances attention

39. Main memory structures & connections Amyg-dala Basolateral limbic circuit Mayes, 2000

40. Want Slides?Please provide email address Video: NoT cue 17-27 minutes Video: Tulving/Milner – Clive cue 6-18 minutes

41. Clive Wearing • R-handed • Above average IQ • Prominent Musician • Herpes Simplex Encephalitis • Bilateral temporal lobe degeneration L>R • Dense Anterograde Amnesia (Wilson & Wearing, 1995)

42. Clive Wearing

43. Frontal Lobes • Tennessee Williams: “Life is all memory except for the present moment that flies by so quickly that you can hardly catch it going by” • WM: moment • LTM: past

44. Baddeley & Wilson, 2002 Video: cue @ 27-33 min Working Memory • Central Executive: Attentional control of the slave systems: • Visuo-spatial sketchpad • Phonological loop • Both derive and feed information to and from LTM • WM is a combination of maintenance and manipulation operations and works in close interaction with LTM

45. Basic WM paradigms • Delayed response • Delayed alternation • Object alternation • Go No-Go • Reversal • Delayed match to sample • Delayed non-match to sample • Recurring stimuli (recall most recent presentation) • Trial-unique stimuli (distinguish familiar from novel)

46. Component processes of WM • Mnemonic • Register (encode) • Store (maintain) • Rehearse • Non-Mnemonic • Control interference (inhibit) • Manipulate • Select (retrieve, prepare) • Respond (motor effector) • Domain-specific sensory systems (spatial, object)

47. Working Memory • Delayed Response Task: • Access spatial information • Hold information on on-line during delay period • Initiate motor response • Delay tasks sensitive to principal suclus • Impaired with lesions • Evidence for delay-specific neurons

48. Working Memory • Shared working memory circuit in humans • BA9/46 (DLPFC) • Posterior Parietal • Left Hemisphere • Delayed response • Delayed alternation • Object alternation • “Guide behavior in the absence of external cues”

49. manipulation scanning encoding Inhibition/selection maintenance CUE RESPONSE DELAY time Functional neuroimaging(D’Esposito et al., 2000; Fletcher & Henson, 2001) • DLPFC • Encoding (supraspan) • Maintenance • Manipulation • Scanning • VLPFC • Maintenance • Rehearsal • Inhibit, select • Anterior PFC (Poles) • More complex manipulation

50. Frontal lobes and working with memory • Associative retrieval: conscious recollection that are cue-driven • medial temporal lobes (MTL) • Strategic Retrieval: problem solving approach to memory where • the frontal lobes work with memories • delivered through the medial temporal lobes and posterior neocortex Video: cue 35 minutes TRAIN