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Abstract:
Benzodiazepines are thought to act primarily on GABA
receptors and might affect sustained attention and working memory
(WM) by increasing GABA-mediated recurrent inhibition. Such
enhancement of inhibitory mechanisms could disrupt the ability to
sustain activation of task-relevant representations. In this study
ten healthy adults received the benzodiazepine alprazolam (1mg) or
a placebo in a within-subject double-blind fashion. EEG data were
collected during two difficulty levels of an "n-back" spatial WM
task and under resting conditions. Alprazolam impaired accuracy and
slowed responses on the WM task, and produced marked subjective
sedation. The drug also affected neurophysiological measures. Under
placebo conditions, increased task difficulty was associated with
an increase in power of the frontal midline theta EEG rhythm, and a
widespread decrease in power in the alpha band. The acute effects
of alprazolam eliminated these task-related changes. Across task
conditions alprazolam increased power in the beta band,
particularly over dorsolateral frontal regions. Alprazolam also
affected attention-related components of the stimulus-locked
event-related potential. Together the results suggest that, in
conjunction with their sedating effect, benzodiazepines impair
performance on WM tasks while changing the oscillatory properties
of cortical neurons and disrupting their responsiveness to
variations in WM task demands. Supported by the NIMH.
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