Fractionation of Memory in Medial Temporal Lobe Amnesia

1. Fractionation of Memory in Medial Temporal Lobe Amnesia Chris M. Bird Tim Shallice Lisa Cipolotti

2. Who? • RH • Female • 58-year-old housewife • Right-sided hippocampal damage • Intact cognitive profile apart from selective memory impairments

3. What Went Wrong? • 1996 • Sudden onset tingling, weakness in the left arm • Impairment in remembering events, appointments, conversations • Difficulty with her sense of direction – esp. in unfamiliar places • However • NO difficulty in remembering names & faces • NO difficulty in recognizing familiar places or landmarks • Neurological examination - normal

4. Nature of the Damage • T1 weighted images • selective atrophy of right hippocampal formation (focused volume loss) • Enlargement of the right lateral ventricle • NO abnormalities in left hippocampus • Other temporal lobe areas appeared normal

5. Nature of the Damage • Brain volume calculated to be within normal range  no evidence of widespread atrophy • Left hippocampus volume = 2654 mm3 • Right hippocampus volume = 1100 mm3 • Right hippocampus markedly small – 58.6% smaller

6. Specific Aspects of Memory Impaired • 2 assessments, 1 year apart • March 2003 & March 2004 • Results • General Cognitive Assessment • Verbal & Performance IQ – remarkably similar scores • Nominal Skills, Visual, & Visuospatial perception – normal • GNT, Object decision, Cube analysis, Number location • Executive processing – normal • WCST, Verbal fluency

7. Specific Aspects of Memory Impaired • Results • Semantic Memory Assessment • Category specific naming test – normal • Able to name all famous buildings, 9/12 famous faces • Category fluency – normal • 8 semantic categories, 3 phonemic categories • 3 comprehension tests – satisfactory • Intact performance on general intelligence, focal language, perception, executive tasks, and extensive semantic memory battery no cognitive decline

8. Specific Aspects of Memory Impaired • Results • Anterograde memory assessment • Story recall tests – weak • Paired associate learning test – lower end of normal range • Visual recall – clearly impaired • Rey-Osterreith complex figure • Failed at learning a spatial supraspan • Recognition Memory Test – normal • Suggests preserved recognition memory for verbal material & unfamiliar human faces

9. Specific Aspects of Memory Impaired • Results • Anterograde memory assessment cont’d • Topographical Recognition Memory Test – poor • Pictures of outdoor urban scenes • Overall, verbal recall & recognition memory (human faces) tests – normal range • Tests of story recall - poor

10. Specific Aspects of Memory Impaired • Results • Doors & People Test • Verbal Subtests • Immediate – intact • Delayed – impaired • Recognition – satisfactory • Visual Subtests • Immediate – impaired • Intact verbal recall & recognition memory • Impaired visual recall

11. What can we learn from this? • Left hippocampus is sufficient to serve both recollection & familiarity of some verbal memoranda • Right hippocampus necessary for recollection & familiarity for topographical materials • Recognition memory for unknown faces not dependent on hippocampus, may depend on other structures

12. Outlook Data from this study appear to support earlier studies that hippocampus plays role in both recollection & familiarity Word of caution on drawing strong conclusions about the neuroanatomy of recollection & familiarity Unclear Which aspects of non-verbal memory can be mediated successfully by areas outside the hippocampus? What treatments are out there that can improve, possibly bring back, non-verbal memory abilities in patients with extensive MTL damage? Discussion

13. Questions?