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Abstract:
Abstract: Primate studies have found visually responsive
neurons distributed beyond cortical areas typically involved in
vision. Among these are premotor cortex, supplementary motor area,
dorsolateral prefrontal cortex, and frontal eye fields. Given these
findings, visual stimulation would be expected to result in
activation of human frontal cortex. However, few
electrophysiological studies have described sensory activations in
frontal regions in response to simple visual stimulation. The
present study further characterized the distribution of
stimulus-related activity over frontal cortex by examination of the
spatiotemporal dynamics of visual event-related potentials (ERPs)
elicited by simple visual stimuli using scalp current density
measures derived from high-density ERP recordings. Hemiretinal
stimuli were viewed passively and during a simple ipsi- or
contramanual reaction time task. The motor requirement was included
to investigate the effects of response preparation on premovement
frontal activations. The results indicate early frontocentral
activation, particularly over the right hemisphere (peak magnitude
124ó148 ms) that is independent of input visual field or
motor response requirement, and that is clearly separate in
timecourse from the posterior responses elicited by visual input.
These findings are in accord with the multiplicity of visual inputs
to frontal cortex and are presented in terms of frontal lobe
functions as may be required in these tasks.
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