Spatiotemporal dynamics of visual attention during saccade preparation: Independence and coupling between attention and movement planning.

During the preparation of a saccadic eye movement, a visual stimulus is more efficiently processed when it is spatially coincident with the saccadic target as compared to when the visual and the saccadic targets are displayed at different locations. We studied the coupling between visual selective attention and saccadic preparation by measuring orientation acuity of human subjects at different locations relative to the saccadic target and at different delays relative to the saccade cue onset. First, we generalized previous results (E. Castet, S. Jeanjean, A. Montagnini, D. Laugier, & G. S. Masson, 2006) revealing that a dramatic perceptual advantage at the saccadic target emerges dynamically within the first 150-200 ms from saccade cue onset. Second, by varying the validity of the spatial cue for the discrimination task, we encouraged subjects to modulate the spatial distribution of attentional resources independently from the automatic deployment to saccadic target. We found that an independent component of attention can be voluntarily deployed away from the saccadic target. The relative weight of the automatic versus the independent component of attention increases across time during saccadic preparation.