Subtypes of working memory performance were examined in a cohort
of 50 HIV-infected adults and 23 uninfected controls using an
n-back paradigm (2-back) in which alphabetic stimuli
were quasi-randomly presented to a quadrant of a computer monitor.
In the verbal working memory condition, participants determined
whether each successive letter matched the letter that appeared
two previously in the series, regardless of spatial location.
In the spatial working memory condition, participants determined
whether each letter matched the spatial location of the letter
that had appeared two previously, regardless of letter identity.
The dependent variable was percent accuracy in each condition.
Results of mixed model ANOVA revealed that the HIV-infected
participants performed significantly worse than controls on
both the verbal and spatial working memory tasks. A significant
main effect for working memory condition was also present with
both participant groups performing better on the spatial working
memory task. These results, the first study of HIV-infected
adults to directly compare verbal versus spatial working
memory performance using the identical test stimuli across task
conditions, suggests that HIV infection is associated with a
decrement in working memory efficiency that is equally apparent
for both verbal and spatial processing. These findings implicate
central executive dysfunction as a likely substrate and provide
the basis for hypothesizing that decline in working memory may
contribute to other HIV-associated neuropsychological deficits.
(JINS, 2002, 8, 532–538.)