Properties of attentional selection during the preparation of sequential saccades.

We examined the allocation of attention during the preparation of sequences of saccades in a dual task paradigm. As a primary task, participants performed a sequence of two or three saccades to targets arranged on a circular array. The secondary task was a two-alternative discrimination in which a critical discrimination stimulus (digital "E" or "3") was presented among distractors either at one of the saccade goals or at any other position. The findings show that discrimination performance is enhanced at all the saccade target locations of the planned sequence, while it is close to chance level at the positions that are not relevant for the saccade sequence. An analysis of the discrimination performance at the intermediate locations indicates that saccade target selection involves spatially distinct, non-contiguous foci of attention. Further, our findings demonstrate that the movement-relevant locations are selected in parallel rather than serially in time. We conclude that during the preparation of a saccade sequence--well before the actual execution of the eye movement--attention is allocated in parallel to each of the individual movement targets.