Amnesia - What is it?

1. Amnesia - What is it? • A selective disruption of the processes underlying long-term memory • Short-term and sensory memory are typically functional • Other cognitive functions are not impaired • Intelligence, attention...

2. Amnesia - What is it? • A selective disruption of the processes underlying long-term memory • Short-term and sensory memory are typically functional • Other cognitive functions are not impaired • Intelligence, attention...

3. Recency vs Primacy • Amnesia patients exhibit recency effect but not primacy effect Long-term memory Short-term memory

4. Amnesia - What is it? • A selective disruption of the processes underlying long-term memory • Short-term and sensory memory are typically functional • Other cognitive functions are not impaired • Intelligence, attention...

5. Retrograde & Anterograde • Retrograde amnesia - Loss of information that was learned before the onset of amnesia • Anterograde amnesia - inability to learn new information after the onset of amnesia • Both can occur in the same patient and commonly do

6. Retrograde & Anterograde • Retrograde amnesia - Loss of information that was learned before the onset of amnesia • Anterograde amnesia - inability to learn new information after the onset of amnesia • Both can occur in the same patient and commonly do

7. Concussion Migraines Hypoglycemia Epilepsy Electroconvulsive shock therapy Specific brain lesions (i.e. surgical removal) Ischemic events Drugs (esp. anesthetics) Infection Psychological Nutritional deficiency Causes of Amnesia

8. Types of memory

9. Proposed types of memory

10. Brain regions associated with human amnesia • Diencephalic amnesia - damage to the medial thalamus and mamillary nuclei • Medial temporal lobe amnesia - damage to the hippocampal formation, uncus, amygdala, and surrounding cortical areas

11. Brain regions associated with human amnesia • Diencephalic amnesia - damage to the medial thalamus and mamillary nuclei • Medial temporal lobe amnesia - damage to the hippocampal formation, uncus, amygdala, and surrounding cortical areas

12. Diencephalic Amnesia • Damage to the medial thalamus and/or mamillary bodies • stroke • Korsakoff’s syndrome • Caused by thiamine deficiency as a result of chronic alcoholism

13. Korsakoff’s symptoms • Anterograde amnesia • Retrograde amnesia • Covers most of the adult life • Lack of insight • Typically unaware of memory problems • Confabulation • Patient makes up stories to fill in the past

14. Medial Temporal lobe amnesia • Hippocampus is most important site of damage

15. Case H.M. • Epileptic patient • Had medial temporal lobes removed to stop seizures • Seizures were reduced but H.M. became severely amnesiac.

16. Case H.M. • His intelligence is above normal • IQ = 112 • Performs normally on all tests of short-term memory • Selective long-term memory impairment

17. Case H.M. Control brain H.M.

18. Case H.M. • Memory impairment for recent events • spans the 3 years prior to his surgery • Capable of recalling childhood memories • Anterograde amnesia was initially thought to be global (all types of memory) • later discovered that certain types of learning are intact

19. Case H.M. • Grave memory impairment for recent events • spans the 3 years prior to his surgery • Capable of recalling childhood memories • Anterograde amnesia was initially thought to be global (all types of memory) • later discovered that certain types of learning are intact

20. Case H.M. • Priming still works • H.M. can still form procedural memories

21. Case H.M. • The Gollin incomplete picture test • subjects asked to identify the object • pictures are shown in sequence from least to most clear • shown the same images at a later date • both amnesiacs and control subjects identify the object at an earlier stage

22. Case H.M. • Mirror drawing task. • Trace figure while looking in a mirror • Control subjects get better at this with repetitive training.

23. Case H.M. • Mirror drawing task • H.M. improved with repeated training. • Procedural memory is intact • He cannot recall ever having performed this task before Day 1 Day 2 Day3

24. Case H.M. • Doesn’t remember the death of his father • Can’t remember or describe his job • Doesn’t remember his examiners

25. Case H.M. • According to our memory dichotomies, what type of memory is the medial temporal lobe (especially the hippocampus) responsible for?

26. Types of memory

27. Case H.M. • H.M.s Retrograde amnesia is temporally graded • remote memory is spared but recent memory is lost • Not all amnesia patients show this pattern • V.C., N.A. have extensive retrograde amnesia (flat gradient)

28. Lessons from amnesia • Existence of Multiple memory systems • Localization of cognitive functions

30. S. • “Photographic” extreme memory ability (a mnemonist) • Able to recall complex test stimuli

31. S. • “Photographic” extreme memory ability (a mnemonist) • Able to recall complex test stimuli • S. used two “strategies” or abilities typical of mnemonists: • rich synesthesia-like quality to his perception of stimuli - leads to stronger associative links • vivid and elaborate mental imagery of things he should remember

32. S. • “ Even numbers remind me of images. Take the number 1. This is a proud, well-built man; 2 is a high-spirited woman; 3 a gloomy person (shy, I don’t Know); 6 a man with a swollen foot...” Luria, A.R. The mind of a mnemonist. 1968 Luria, A.R. The man with a shattered world. 1972