The conjoint influence of spatial selective attention and motor set on very short latency VERs.

This study investigated whether motor set, in conjunction with spatial selective attention (sensory set), influences the transmission of incoming visual information at a precortical level in humans. Stimuli were presented concomitantly in both the right and left visual fields while subjects attended to the relevant visual field (either left or right) on a given trial, and was prepared to make one of three kinds of responses (an eye movement, foot-lift, or counting) to target stimuli appearing in that field. VERs were obtained from frontal and parietal sites. A deflection falling within a 40-70 msec range was more negative under the attend than under the unattend condition for the eye movement task, the opposite being the case for the counting task. No attention effect was found for the foot-lift task. The findings were interpreted as providing support for the precortical hypothesis.