Schiller PH; Kendall, GK, Slocum, WM, Tehovnik, EJ
Visual Neuroscience, 25(5-6), 661-73.
Abstract
In this study we examined procedures that alter saccadic latencies and target
selection to visual stimuli and to electrical stimulation of area V1 in the
monkey. It has been shown that saccadic eye-movement latencies to singly presented
visual targets form a bimodal distribution when the fixation spot is turned
off a number of milliseconds prior to the appearance of the target (the gap
period); the first mode has been termed express saccades and the second regular
saccades. When the termination of the fixation spot is coincident with the appearance
of the target (0 ms gap), express saccades are rarely generated. We show here
that a bimodal distribution of saccadic latencies can also be obtained when
an array of visual stimuli is presented prior to the appearance of the visual
target, provided the elements of the array overlap spatially with the visual
target. The overall latency of the saccadic eye movements elicited by electrical
stimulation of area V1 is significantly shortened both when a gap is introduced
between the termination of the fixation spot and the stimulation, and when an
array is presented. However, under these conditions, the distribution of saccadic
latencies is unimodal. When two visual targets are presented after the fixation
spot, introducing a gap has no effect on which target is chosen. By contrast,
when electrical stimulation is paired with a visual target, introducing a gap
greatly increases the frequency with which the electrical stimulation site is
chosen.