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Research Article Inactivation of macaque lateral intraparietal area

Summary: Research Article
Inactivation of macaque lateral intraparietal area
delays initiation of the second saccade
predominantly from contralesional eye positions in a
double-saccade task
Chiang-Shan Ray Li1, 2 and Richard A. Andersen1,
Received: 8 December 1999 / Accepted: 29 June 2000 / Published online: 8 February 2001
Abstract. Previous studies have shown that, although lateral intraparietal (LIP) area neurons have
retinotopic receptive fields, the response strength of these cells is modulated by eye position. This
combining of retinal and eye position information can form a distributed coding of target locations in a
head-centered coordinate frame. Such an implicit head-centered coding offers one mechanism for
maintaining spatial stability across eye movements and can be used to compute new oculomotor error
vectors after each eye movement. An alternative mechanism is to use eye displacement signals rather
than eye position signals to maintain spatial stability. The aim of this study was to distinguish which of
these two extraretinal signals (or perhaps both signals) are employed in a double saccade task, which
required the monkey to use extraretinal information associated with the first saccade to localize a
remembered target for a second saccade. By varying the direction and the end point of the first saccade
and selectively inactivating area LIP in one hemisphere with muscimol injection, we were able to
distinguish between the two mechanisms by observing how the second saccade was impaired in this
task. The displacement mechanism predicts that, if the first saccade is in the contralesional direction, the


Source: Andersen, Richard - Division of Biology, California Institute of Technology


Collections: Biology and Medicine