Article

Despite the traditional view that damage to the hippocampus and/or surrounding
areas of the medial temporal lobe (MTL) does not impair short-term or working
memory (WM), recent research has shown MTL amnesics to be impaired on WM tasks
that require maintaining a small amount of information over brief retention
intervals (e.g., maintenance of a single face for one second). However, the types
of tasks that have demonstrated WM impairments in amnesia tend to have involved
novel stimuli. We hypothesized that WM may be impaired in amnesia for tasks that
require maintaining novel information, but may be preserved for more familiar
material, particularly if the material can be easily rehearsed. To test this
hypothesis, patient HC, a 22-year-old developmental amnesic with relatively
preserved semantic memory and 20 age and education matched controls performed a
delayed match-to-sample task that required maintaining a single famous or
non-famous face for 1-8s, digit span and reading span tasks, and a modified
Brown-Peterson task that required maintaining a single high- or low-frequency
word or a non-word for 4-8s. HC's performance was impaired for non-famous faces
but preserved for famous faces, impaired for the reading span task but preserved
for digit span, and it was impaired for non-words and unfamiliar low-frequency
words but preserved for familiar words. These results support the hypothesis that
an intact hippocampus is necessary for maintaining a single novel stimulus in WM.
However, stimulus familiarity and rehearsal support WM via cortical regions
independent of the MTL.
CI - Copyright (c) 2011 Elsevier Ltd. All rights reserved.

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