Erroneous Prosaccades in a Gap-Antisaccade-Task

Abstract

In an antisaccade-task subjects are required to look to the side opposite of a suddenly presented stimulus so that the voluntary and the reflexive components operate in opposite directions. In this study the gap-antisaccade- and the overlap-prosaccade-task were used to investigate the number of erroneous prosaccades in the antisaccade-task, their reaction times, and their correction times in relation to the number of express saccades a same subject produced in the overlap-prosaccade-task. Out of 234 subjects 126 were selected who produced more than 20 % errors. Among the data sets we differentiated between a “fast” group with many express saccades and a “slow” group with only a few express saccades in the overlap-prosaccade-task. Both groups showed differences in the reaction and correction time of their errors. In a second experiment we wanted to know whether the subjects (N=38) recognized their errors and whether a recognized sequence of an erroneous prosaccade and the corrective saccade is different from an unrecognized sequence. The results indicate that for each subject one has to differentiate between the disability to suppress reflex-like saccades due to an insufficient fixational control or due to a weak voluntary control or the disability to generate voluntary saccades. The erroneous prosaccades and their corrections escape the conscious perception in many cases despite large (4°+8°) and long lasting (>100 ms) changes of the retinal image. It is discussed that the perceptual spatial frame transforms differently prior to voluntary as compared to involuntary saccades.