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RAPID COMMUNICATION Change in Motor Plan, Without a Change in the Spatial Locus of

Change in Motor Plan, Without a Change in the Spatial Locus of
Attention, Modulates Activity in Posterior Parietal Cortex
Division of Biology, California Institute of Technology, Pasadena, California 91125
Snyder, Lawrence H., Aaron P. Batista, and Richard A. Ander- recorded for off-line analysis. A square array of eight 3.2-cm but-
sen. Change in motor plan, without a change in the spatial locus tons surrounding a central fixation button, each of which could be
of attention, modulates activity in posterior parietal cortex. J. Neu- lit by a red or green LED, was located 28 cm from the eyes,
rophysiol. 79: 28142819, 1998. The lateral intraparietal area subtending 30 1 30 of visual angle. Extracellular potentials were
(LIP) of macaque monkey, and a parietal reach region (PRR) recorded using tungsten electrodes inserted through a recording
medial and posterior to LIP, code the intention to make visually cylinder centered at 5 mm posterior and 12 mm lateral (Horsley-
guided eye and arm movements, respectively. We studied the effect Clarke coordinates). Single cells were isolated while animals per-
of changing the motor plan, without changing the locus of attention, formed delayed saccades and reaches to one of the eight peripheral
on single neurons in these two areas. A central target was fixated red or green LEDs. Data were collected from cells that had excit-
while one or two sequential flashes occurred in the periphery. The atory responses before movement to at least one target.
first appeared either within the response field of the neuron being The effect of changes in motor intention was studied in two
recorded or else on the opposite side of the fixation point. Animals adult male rhesus monkeys. Trials began with 750 ms of central
planned a saccade (red flash) or reach (green flash) to the flash light fixation in an otherwise dark room (Fig. 1). A peripheral
location. In some trials, a second flash 750 ms later could change flash on opposite sides of the fixation point and either inside or
the motor plan but never shifted attention: second flashes always outside the receptive field instructed a saccade (red) or a reach


Source: Andersen, Richard - Division of Biology, California Institute of Technology
Snyder, Larry - Department of Anatomy and Neurobiology, Washington University in St. Louis


Collections: Biology and Medicine