Prefrontal cortical representation of visuospatial working memory in monkeys
examined by local inactivation with muscimol.
Sawaguchi, Toshiyuki, and Michiyo Iba.
Laboratory of Neurobiology, Hokkaido University School of Medicine, N15 W7,
Kita-ku, Sapporo 060-8638, Japan; CREST, Japan Science and Technology
APStracts 8:0232J, 2001.
In primates, dorsolateral areas of the prefrontal cortex (PFC) play a major role in
visuospatial working memory. To examine the functional organization of the PFC for
representing visuospatial working memory, we produced reversible local inactivation,
with the local injection of muscimol (5 µg, 1µl), at various sites (n=100) in the
dorsolateral PFC of monkeys and observed the behavioral consequences in an
oculomotor delayed-response task that required memory-guided saccades for locations
throughout both visual fields. At 82 sites, the local injection of muscimol induced
deficits in memory-guided saccades to a few specific, usually contralateral, target
locations that varied with the location of the injection site. Such deficits depended on the
delay length, and longer delays were associated with larger deficits in memory-guided
saccades. The injection sites and affected spatial locations of the target showed a gross
topographical relationship. No deficits appeared for a control task in which the subject
was required to make a visually guided saccade to a visible target. These findings
suggest that a specific site in the dorsolateral PFC is responsible for the working memory
process for a specific visuospatial coordinate to guide goal-directed behavior. Further,
memoranda for specific visuospatial coordinates appear to be represented in a
topographical memory map within the dorsolateral PFC to represent visuospatial working
memory processes.
Received 20 November 2000; accepted in final form 21 May 2001
APS Manuscript Number J830-0.
Article publication pending Am J Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 31 July 2001