The increased reaction time of antisaccades. What makes the difference?

The aim of this study was the detection of the parameters involved in an already defined phenomenon, namely that the reaction time of antisaccades is greater than that of pro-target saccades. Thus, we performed four different experimental paradigms: (i) The target location was unpredictable (to the left or to the right) but the type of saccade (pro-or anti-target) was predictable. The corresponding mean values of the reaction times were 231 +/- 40 ms for anti- and 179 +/- 50 ms for pro-target saccades. (ii) Both the target position and the type of saccade were unpredictable (437 +/- 91 and 412 +/- 85 for anti-and pro-target saccades, respectively). (iii) The target location remained predictable while the type of saccade was unpredictable (397 +/- 104 and 385 +/- 90 ms) and (iv) Both the target position and the type of saccade were predictable (185 +/- 67 and 180 +/- 61). The statistical analysis (ANOVA and post hoc comparisons) revealed significant differences only in the first two experiments. Our results suggest that the antisaccades present increased latency, compared to that of pro-target saccades, only under certain experimental conditions and especially when the target location is unpredictable. We presume that the antisaccade's latency prolongation is due not to the frontal lobe inhibition but to the double interference of the parietal lobe, which has to re-reconstruct the target location in space.