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Last Lecture

+. Last Lecture. Frontal Lobe Anatomy Inhibition and voluntary control A model task: working memory . This Lecture. Long Term Memory role of hippocampus in consolidation role of frontal regions in encoding and retrieval right frontal regions and representation of self. Announcements.

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Last Lecture

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  1. + Last Lecture • Frontal Lobe Anatomy • Inhibition and voluntary control • A model task: working memory

  2. This Lecture • Long Term Memory • role of hippocampus in consolidation • role of frontal regions in encoding and retrieval • right frontal regions and representation of self...

  3. Announcements FINAL EXAM: • 182 Dennison • Wednesday, 4/19 • 4:00 pm - 6:00 pm. • Please contact us immediately if this poses a conflict.

  4. Long Term Memory and its Dysfunction • Memory: the ability to retain & recollect the contents of our experience • typically multimodal • rich in associations • The ability to acquire new skills & demonstrate improved performance as a result of experience.

  5. Human Amnesia • Anterograde: Inability to acquire NEW memories. • Retrograde: Inability to recollect OLD memories.

  6. Human Amnesia • Scoville & Milner (1957) H.M. bilateral removal of hippocampus (medial temporal lobes). • Wada testing to avoid bilateral hippocampectomies. • Unilateral removals: material-specific deficit: (Right- nonverbal; Left: verbal)

  7. Case H.M.-- PROFOUND ANTEROGRADE AMNESIA • High Average intelligence • STM: normal- digit span 7 forward; 5 backward • Can converse normally, perform mental math • No post-operative personality changes • Unable to acquire new memories... • all modalities • all material (verbal, nonverbal) • names, people, places, events, route finding • all are affected. surgery Retrograde Anterograde

  8. Early animal models of HM were unsuccessful WHY?(Hint: remember what happened with blindsight) • Testing the wrong type of memory What Amnesics can learn: • Milner (1962) mirror drawing • Warrington & Weiskrantz (1968) perceptual learning (degraded cues, priming) • Weiskrantz & Warrington (1979) classical conditioning

  9. Types of Long Term Memory

  10. Declarative/Explicit • consciously accessible • Episodic: personal/public episodes • Semantic: facts, events, routes • Tested with recall / recognition: • "Have you seen this before?"; "Can you remember...?"; "Is this one of the items you studied...?”

  11. Nondeclarative/Procedural/Implicit • Does not require conscious recollection Examples: • conditioning • skills (motor skills, mirror reading) • priming (e.g. stem completion)

  12. Skill Acquisition • Mirror drawing improves • Amnesics = Controls

  13. Phase 1 Read & rate words (living/non): Lead Bear Fear Work... Phase 2 EXPLICIT TEST: "Complete stem with a word you just read" lea_ bea_ OR IMPLICIT TEST: "Complete stem with first word that comes to mind" lea_ ---> lead or leaf bea_ ---> beat or bear An example of the dichotomy...

  14. Priming is spared in Amnesia • Amnesics cannot recall study items. • But stored representation is accessed automatically.

  15. The Hippocampal circuit & Explicit Memory • Hippocampus - part of a circuit with input to & from parietal, temporal, frontal lobes & limbic system (amygdala).

  16. Hippocampus

  17. The Hippocampal circuit & Explicit Memory • Hippocampus - part of a circuit with input to & from parietal, temporal, frontal lobes & limbic system (amygdala). • CA1 , CA2 , CA3 layers of HPC form a circuit allowing access to cortex • CA1 layer - sensitive to anoxia & epileptic activity (CASE R.B.) • Damage to HPC or its inputs/outputs --> LTM impairment

  18. Role of Hippocampus in Explicit Memory • NOT the location of LTM • NOT necessary for retrieval of LTM • NOT the location of STM • HPC: immediate experience --> LT memories CONSOLIDATION • Explicit memory - stores single events w/ context. • Learning is fast (one-trial learning-- but forgetting endures). • Representations are • accessible by various cognitive systems • modality-general • give rise to sense of familiarity.

  19. Implicit memory... • Reactivation of the processing structures engaged during learning. • Learning is incremental, gradual, slow • Representations are specific to a task and or the learning modality. • Involves multiple systems (cortex, basal ganglia) More on the encoding and retrieval of explicit LTM...

  20. Frontal Contributions to LTM Recency Judgments knowledge of temporal context • give a list of items • probe w/ two items asking: “Which one of these items came most recently?”

  21. Marco Polo was Venetian Mt. Everest Keeps growing Frontal Contributions Source Memory • ability to identify (remember) the context in which a memory was acquired • task: judge which of two characters uttered a particular fact. Hypno Psyduck

  22. HERA: Hemispheric Encoding/Retrieval Asymmetry (Tulving et al., 1994) PET studies w/normal subjects show • Left Hem. is critical to encoding into LTM • Lateral Prefrontal areas • all materials: verbal & nonverbal • Why? associating meaning with events • Right Hem. is critical to retrievalfrom LTM • Lateral Prefrontal areas • all materials: verbal & nonverbal • Why? memory requires reflection about self / personal experience

  23. Right Frontal Lobe & Self Craik et al., 1999 - PET study with 4 conditions How well does the word stubborn describe... • You? • Lee Bollinger? • How socially desireable? • How many syllables? • RESULT: Only self-referential instruction activated Right prefrontal cortex ( same areas activated by memory retrieval) • Conclusion: Right frontal regions are important for representation of self.

  24. Memory Summary • WM vs. LTM LTM: IMPLICIT vs. EXPLICIT • Explicit (personal episodes, semantics/facts) • Amnesia -- anterograde or retrograde • Establishing new explicit memories requires • encoding, consolidation, retreival • hippocampus -- consolidation (HM & RB) • HERA: • Left frontal- encoding (context info) • Right frontal- retrieval (self)

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