Effects of optic flow in motor cortex and area 7a.
Merchant, H., A. Battaglia-Mayer, A. P. Georgopoulos .
1Brain Sciences Center, Department of Veterans Affairs Medical Center, Minneapolis
MN 55417, USA; 2Department of Neuroscience, University of Minnesota Medical
School, Minneapolis MN 55455, USA; 3Department of Neurology, University of
Minnesota Medical School, Minneapolis MN 55455, USA; 4Department of Psychiatry,
University of Minnesota Medical School, Minneapolis MN 55455, USA; and 5Cognitive
Sciences Center, University of Minnesota, Minneapolis MN 55455, USA.
APStracts 8:0231J, 2001.
Moving visual stimuli were presented to behaving monkeys who fixated their eyes and
did not move their arm. The stimuli consisted of random dots moving coherently in eight
different kinds of motion (right-, left-, up-, down-ward, expansion, contraction,
clockwise, counterclockwise) and were presented in 25 square patches on a LCD
projection screen. Neuronal activity in the arm area of the motor cortex and area 7a was
significantly influenced by the visual stimulation, as assessed using an analysis of
variance. The percentage of cells with a statistically significant effect of visual
stimulation was 3x greater in area 7a (370/587, 63%) than in motor cortex (148/693,
21.4%). With respect to stimulus properties, its location and kind of motion had
differential effects on cell activity in the two areas. Specifically, the percentage of cells
with a significant stimulus location effect was ~2.5x higher in area 7a (311/370, 84%)
than in motor cortex (48/148, 32.4%), whereas the percentage of cells with a significant
stimulus motion effect was ~2x higher in the motor cortex (79/148, 53.4%) than in area
7a (102/370, 27.6%). We also assessed the selectivity of responses to particular stimulus
motions using a Poisson train analysis and determined the percentage of cells that showed
activation in only one stimulus condition. This percentage was 2x higher in the motor
cortex (73.7%) than in area 7a (37.7%). Of all kinds of stimulus motion tested, responses
to expanding optic flow were the strongest in both cortical areas. Finally, we compared
the activation of motor cortical cells during visual stimulation to that observed during
force exertion in a center º out task. Of 514 cells analyzed for both the motor and visual
tasks, 388 (75.5%) showed a significant relation to either or both tasks, as follows:
284/388 (73.2%) cells showed a significant relation only to the motor task, 27/388 (7%)
cells showed a significant relation only to the visual task, whereas the remaining 77/388
(19.8%) cells showed significant relations to both tasks. Therefore, a total of 361/514
(70.2%) cells were related to the motor task and 104/514 (20.2%) were related to the
visual task. Finally, with respect to receptive fields (RFs), there was no clear visual
receptive field structure in the motor cortical neuronal responses, in contrast to area 7a
where RFs were present and could be modulated by the type of optic flow stimulus.
Received 14 November 2000; accepted in final form 21 May 2001
APS Manuscript Number J822-0.
Article publication pending Am J Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 31 July 2001