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Anna Montagnini, Eric Castet; Presaccadic deployment of attention: what is the trigger?. Journal of Vision 2008;8(6):109. doi: 10.1167/8.6.109.
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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 saccadic targets are displayed at different locations. We have previously characterized the time-course of this selective deployment of visual resources (visual attention) to the saccadic target, by means of a dual task, where the execution of a saccade constitutes the primary task, while an orientation discrimination judgment at different moments and locations during saccade preparation is the secondary task. We have shown that a dramatic selective improvement of discrimination performance at the saccadic target is achieved within 150–200ms and this dynamics represents a characteristic signature of saccade preparation across several experimental conditions. Some electrophysiological and modelling studies have recently suggested that a presaccadic attentional enhancement in early visual areas should be time-locked to saccade onset. This enhancement could represent the neuronal substrate of the observed perceptual advantage at the saccade target. To address this hypothesis, we tested whether, in human subjects, the characteristic time-course of the selective visual improvement at saccadic target is locked in time to the onset of the eye movement. For this purpose we aimed at decorrelating across trials the time delay between cue and visual probe from the time delay between visual probe and saccade onset. In particular, we wanted to broaden the distribution of saccadic latency. In order to do this we modified our dual task in two different ways (Go-NoGo task and different cue duration task), such that the decoding of central visual instruction becomes more compelling, thereby increasing latency variability. Our results show no significant improvement of visual performance as a function of temporal proximity to saccade onset, questioning the time-locking hypothesis.
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