Delayed Saccades, but Not Delayed Manual Aiming Movements, Require Visual Attention Shifts

Several studies have shown that during the preparation of a goal-directed movement, perceptual selection (i.e., visual attention) and action selection (the selection of the movement target) are closely coupled. Here, we study attentional selection in situations in which delayed saccadic eye movements and delayed manual movements are prepared. A dual-task paradigm was used which combined the movement preparation with a perceptual discrimination task. The results demonstrate a fundamental difference between the preparation of saccades and of manual reaching. For delayed saccades, attention is pinned to the saccade target until the onset of the response. This does not hold for manual reaching, however. Although fast reaching movements require attention, reaches delayed more than 300 ms after movement cue onset can be already performed "off-line"; that is, attention can be withdrawn from the movement target.