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Abstract:
We tested if single cells in posterior parietal cortex
combine saccadic eye movement signals with reach intention signals.
Macaque monkeys made delayed eye or arm movements to peripheral red
or green targets, respectively, located 12 d from the fovea at 45 d
intervals. The parietal reach region was identified as a region
that showed selective delay period activity when reaches but not
saccades were planned. Despite reach-specific activity during the
delay, 33 of 100 cells also had saccade-related activity at the end
of the delay period when an eye movement had been instructed. The
delay activity for cells with saccadic activity was only slightly
less selective than for cells without, with mean ratios of activity
during the delay epoch of 1.8:1 (reach:saccade) versus 2.1:1,
respectively. The mean preferred direction for saccadic activity
differed from that for reach-related delay activity by only 12 d.
These observations indicate that many cells in the parietal reach
region combine intended reach activity with saccadic responses.
Such a conjunction of signals could be related to eye-hand
coordination. Alternately, if intended reach activity is stored in
an eye-centered frame, eye movement information could be used to
update reach intention activity after each saccade.
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