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Abstract:
Abstract: Spatial coding in the posterior parietal cortex
shows some specialization for movement selection, with the lateral
intraparietal area (LIP) specialized for saccades, and the parietal
reach region (PRR) for limb movements. Area LIP codes visual
saccade targets in eye coordinates , and a majority of LIP neurons
also code auditory targets in eye coordinates. Such coding can
specify the targets in motor error coordinates, i.e. the direction
and amplitude of the saccade needed to foveate the target. We
recently examined the spatial reference-frame in PRR. Surprisingly,
PRR cells do not generally code planned reaches in the limb-centred
coordinates that would specify the direction and amplitude of the
required reach for a target. Rather, PRR neurons code both visual
and auditory targets predominantly in eye-centered coordinates.
Moreover, activity in PRR related to an impending reach is updated
in eye-coordinates to compensate for intervening saccades. This
predominance of eye-centered coding may be computationally
efficient. The response of LIP and PRR neurons is modulated by
eye-, head- and limb-position, and this gain modulation may provide
mechanisms for transformation into head-, body-, and limb-centered
coordinates.
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