| |
Abstract:
Abstract: We studied a 56 year old female who suffers from
selective retrograde amnesia for the time period from childhood
until debut of encephalitis. Objectives were to study the
localization of lesion, and use ERP and behavioral tests to seek
evidence of memory representations not consciously remembered. MRI
scanning was performed. News archives and interviews with a close
relative were used to gather information about relevant life
events. Knowledge was probed by presenting descriptive sentences
with true or false final words (probes), with ERP recorded to the
probes. Later she made a forced choice between true and the false
versions of each sentence, and indicated the basis for response
(knowledge, recollection, or guessing). MRI showed bilateral,
predominantly right sided changes involving the hippocampus and
amygdala. She had a localized lesion in the depth of the right
frontal lobe possibly involving fiber tracts connecting temporal
and frontal areas. She had no conscious recollections from the
amnesic period, but sentence verification trials showed significant
overweight of correct guesses. Single sweep ERPs showed significant
discrimination between true and false probes. Her lesion is
consistent with hypotheses of the central role of right hemisphere
fronto-temporal regions in retrograde memory. Memory performance
reflects a feeling of guessing about the amnesic period, but ERP
and behavioral data show evidence of preserved information. Her
intact performance could stem from an implicit memory
system.
|
