Effects of stimulus conditions on the performance of antisaccades in man

Abstract

We investigated the effect of different spatial and temporal parameters on the saccadic reaction times (SRTs) of the antisaccades and on the frequency and the SRTs of erratic prosaccades in five adult human subjects. The subjects were instructed to aim their saccades to the side opposite to where a visual go-stimulus occurred. Parameters under consideration were: the gap duration (between 0 and 600 ms, and an overlap paradigm); the stimulus size (sizes of 0.1 degrees, 0.2 degrees, and 0.4 degrees, using the gap 200-ms paradigm); and the stimulus eccentricity (1 degree, 2 degrees, 4 degrees, 8 degrees, and 12 degrees, with the gap 200-ms paradigm). A decrease in the anti SRTs and an increase in the error rate were observed with medium gap durations (200 ms, 250 ms), while the anti-SRTs were longer and the error rates lower with the shorter values (0 ms, 100 ms, and with the overlap paradigm) and with the long values (600 ms). A slight decrease in the anti-SRTs and an increase in the error frequency occurred with increasing eccentricity; the SRT distributions of the errors resembled closely those of prosaccades in corresponding prosaccade tasks with the same eccentricities. The stimulus size had only modest or no effects at all. Analysis of the distributions of the correction times of the erratic prosaccades showed that the intersaccadic intervals could be very short: in the range of express saccades, with a peak at 100 ms or in some subjects even shorter, with a peak at 40-50 ms. It is concluded that the performance of antisaccades is influenced by parameters that interact with the fixation and/or attention system of oculomotor control. Parameters supporting a disengagement of fixation at the time of stimulus onset provoke a reduction of the saccadic reaction times not only of prosaccades but also of antisaccades. Moreover, a certain state of disengagement seems to facilitate the occurrence of reflex-like errors.

Influence of Stimulus Eccentricity and Direction on Characteristics of Pro- and Antisaccades in Non-Human Primates

“…It is tempting to assume that this may be due to potential overtraining with these locations. However, this cannot account for the fact that similar trends have been reported in other studies employing both non-human primates (Boch et al 1984) and humans (Fischer and Weber 1997;Kalesnykas and Hallett 1994; J. M. Dafoe, J. R. Broughton, I. T. Armstrong, and D. P. Munoz, unpublished data). The apparent bias toward certain stimulus locations could, therefore represent a neurological bias in the actual oculomotor system.…”

“…Hemifield preferences in humans may also be influenced by societal/cultural effects. Previous human studies have reported biases in SRT and direction errors favoring the initiation of rightward saccades compared with leftward saccades (Fischer and Weber 1997;; J. M. Dafoe, J. R. Broughton, I. T. Armstrong, and D. P. Munoz, unpublished results) This bias may be due, in part, to differences associated with reading patterns (i.e., horizontal-left-to-right) (Abed 1991) and would explain the absence of this trend in animals. If the oculomotor system is indeed optimized for generating saccades to certain locations, this would explain, in part, why the monkeys had particular difficulties in performing antisaccades to certain locations.…”

“…P. Munoz, M. C. Dorris, M. Pare, and S. Everling, unpublished data). Furthermore the presence of a gap period also facilitates the occurrence of express saccades (see Fischer and Weber 1997;Pare and Munoz 1996 for review). Express antisaccades, however, were not generated by either monkey.…”

Nicotine differentially modulates antisaccade performance in healthy male non-smoking volunteers stratified for low and high accuracy

“…There are two published studies examining the effects of stimulus eccentricity on antisaccade latencies in human subjects. In a study by Fischer and Weber (1997), a decrease in antisaccade latencies was seen with increasing stimulus eccentricity (ranging from 1° to 12° stimulus eccentricity). Fischer and Weber also found that antisaccade error rate increased with increasing eccentricity (Fischer & Weber 1997).…”

“…In a study by Fischer and Weber (1997), a decrease in antisaccade latencies was seen with increasing stimulus eccentricity (ranging from 1° to 12° stimulus eccentricity). Fischer and Weber also found that antisaccade error rate increased with increasing eccentricity (Fischer & Weber 1997). On the contrary, Dafoe et al (2007) did not find a significant effect of eccentricity on antisaccade latencies.…”