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This thesis investigated the visual perceptual consequences of reflexive eye movements in humans. A multimodal approach involving the modulation of exogenous attention, and the perturbation of the right frontal eye field (rFEF), explored visual perceptual and oculomotor control functions. Stimulation of the rFEF by TMS and the presentation of stimuli (cues) in order to orient attention, were combined with the measurement of brain activity with EEG, and eye tracking. These methods allowed the investigation of brain function and cognitive processing during a task combining visually driven eye movements with visual motion discrimination. Perturbation of the rFEF provided evidence of dissociable roles in visual perception, shown by a facilitatory effect during involuntary eye movements and an inhibitory effect during eye movement suppression. The rFEF TMS effect at the behavioral level was accompanied by posterior alpha power modulation. Not only the visual perceptual but also the oculomotor control function of the rFEF were affected by TMS, as shown by the reduction in eye movement velocity. The modulation of attention by the presentation of cue stimuli led to effects that were not dependent on eye movements: a facilitatory effect of exogenous orienting of attention was observed when the motion discrimination task was performed simultaneously with the generation of reflexive eye movements, and again also during movement suppression. The effect of attention was reflected in EEG correlates of early visual perceptual processing. Taken together, these results allow generalization to real-world contexts or clinical conditions where visual perception may be compromised by involuntary or pathological eye movements, highlighting the fact that even during reflexive movements the potential involvement of attention is essential for understanding cognitive processing. |
