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The anti-saccade task (AST) is widely used in experimental, clinical, and neuroscience research as a pronounced test of executive functions. AST research includes to some extent also the investigation into its cognitive correlates. In the present study, we have examined cognitive correlates of the AST in the short-term/working memory, executive functions, and intelligence domains in healthy adults. We have obtained the following results. In line with previous research, the global percentage of direction errors PDE comprised of two only negligibly correlated components, direction errors with express or regular latencies. Substantial correlations with the other cognitive measures were obtained only for regular direction errors and, less so, for the global PDE. Results add to the evidence that distinguishes express and regular direction errors and underline that the complex requirements of the AST are reflected in a comparatively rich set of non-redundant parameters.

A vast knowledge exists about saccadic reaction times (RT) and their bi- or multimodal distributions with very fast (express) and regular RT. Recently, there has been some evidence that the smooth pursuit system may show a similar RT behavior. Since moving targets usually evoke a combined pursuit/saccade response, we asked which processes influence the initiation of pursuit and saccadic eye movements. Furthermore, we investigated whether and how the pursuit and saccadic system interact during the initiation of eye movements to moving targets. We measured the RT of the initial smooth pursuit (iSP) response and of the first corrective saccade and compared the RT behavior of both. Furthermore we compared the behavior of the corrective saccades to moving targets to that of saccades to stationary targets, known from the literature. The stimulus consisted of a target that moved suddenly at constant velocity (ramp). In addition, prior to the movement, a temporal gap, a position step or a combination of both could occur (gap-ramp, step-ramp, gap-step-ramp, respectively). Differently from most previous studies, we chose step and ramp with the same direction to provoke competition between the pursuit and saccade system. For the first time we investigated pursuit initiation in “express-saccade makers” (ES makers), a subject group known to produce an abnormally high percentage of short-latency saccades in saccade tasks. We compared their results with subject groups who were either naive or trained with respect to saccade tasks. The iSP started at approximately 100 ms, which corresponds to express saccade latencies. These short iSP-RT occurred reflex-like and almost independent of the experimental task. A bimodal frequency distribution of RT with a second peak of longer iSP-RT occurred exclusively in the ramp paradigm. The RT of the first corrective saccades in a pursuit task were comparable with that in a saccade task and depended on the stimulus. The ability of ES makers to produce a high number of express saccades was transferred to corrective saccades in the pursuit task, but not to pursuit initiation. In summary, short-latency pursuit responses differ from express saccades with respect to their independence of experiment and subject group. Therefore, a simple analogy to express saccades cannot be drawn, although some mechanisms seem to act similarly on both the pursuit and the saccade system (such as disengagement of attention with the gap effect). Furthermore, we found evidence that the initial pursuit response and the first corrective saccade are processed independently of each other. The first corrective saccades to moving targets behave like saccades to stationary targets. Normal pursuit but abnormal saccade RT of ES makers can be explained by recent theories of superior colliculus (SC) function in terms of retinal error handling.

In express-saccade makers a large incidence of express saccades (latencies around 100 ms) is paralleled by a reduced ability to suppress saccade generation when required. Such a behavior occurs frequently in dyslexies. We studied the latencies and the metrical properties of saccades in the very rare case of an adult, nondyslexic express-saccade maker (male, age 29 years). The subject produced 65–95% express saccades in the gap (fixation point removed 200 ms before target onset) as well as in the overlap (fixation point not removed) paradigm, which qualified the subject as the most clear case of an express-saccade maker found so far. The number of express saccades increased rather than decreased when fixation foreperiod, gap duration, and target location were randomized from trial to trial as compared to when they remained constant. In the memory-guided saccade and in the antisaccade paradigms in which immediate saccade execution to a visual target had to be suppressed, the subject often reacted to the target with express saccades in an involuntary way. The amplitudes of express saccades were — in some conditions — found to progressively decrease with increasing latency, giving rise to amplitude transition functions. The present findings disprove the notion that express saccades are generated based on the prediction of the time and location of target appearance and support the notion that they are the result of an optomotor reflex. It is argued that the operation of the reflex is gated by a separate fixation system. Express-saccade makers are described as subjects with a dysfunction of the fixation system. Recent neurophysiological findings suggest that the subject studied in the present study has a selective dysfunction of the fixation system at the level of the superior colliculus.