Fractionation of Memory in Medial Temporal Lobe

Amnesia

Chris M. Bird

Tim Shallice

Lisa Cipolotti

Who?RHFemale58-year-old housewifeRight-sided hippocampal damageIntact cognitive profile apart from

selective memory impairments

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

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

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

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

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

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

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

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

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

Discussion 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?

Questions?