Abstract
The classic AABB task-switching paradigm has demonstrated that a prosaccade completed after an antisaccade elicits longer response latencies, reduced online trajectory amendments and less accurate endpoints than the second of two consecutively completed prosaccades (i.e., the prior-antisaccade effect; Weiler and Heath, 2012: Exp Brain Res). In the current investigation, we sought to determine whether the prior-antisaccade effect arises from the top-down requirements of the recently completed mirror-symmetrical response (i.e., response suppression and vector inversion) or is related to an explicit task ordering effect. To accomplish that objective, participants completed pro- and antisaccades to a briefly presented target (50 ms) in left and right visual space in two saccade task-switching blocks. In one block the AABB task-switching paradigm was employed wherein pro- and antisaccades were alternated on every second trial. In the other block, pro- and antisaccades were pseudo-randomly interleaved on a trial-by-trial basis thus preventing participants from predicting the nature of the upcoming task. Importantly, both blocks were equated for response-repetition (i.e., pro- or antisaccade followed by the same task) and response-switch (i.e., pro- or antisaccade followed by the opposite task) trials. To index online control, we computed the proportion of variance explained by the spatial location of the eye at normalized increments of movement time relative to the eye’s ultimate endpoint. Results demonstrated that response-switch prosaccade trials yielded longer latencies and fewer online corrections compared to their response-repetition counterparts. Notably, this pattern was not modulated across the AABB and pseudo-randomized trial blocks. Thus, a priori knowledge related to the nature of an upcoming task (i.e., pro- or antisaccade) does not account for the prior-antisaccade effect. Rather, we propose that the top-down requirements of the antisaccade result in a systematic inhibition of the oculomotor networks that support the planning and control of subsequent prosaccades.
Meeting abstract presented at VSS 2012