A dorsal fronto-parietal network, including regions in intra-parietal sulcus (IPS) and frontal eye field (FEF), has been hypothesized to control the allocation of spatial attention to environmental stimuli. One putative mechanism of control is the de-synchronization of electroencephalography (EEG) alpha rhythms (~8-12 Hz) in parieto-occipital cortex in anticipation of a visual target. We show that brief interference by transcranial magnetic stimulation (rTMS) with preparatory activity in right IPS or right FEF while subjects attend to a spatial location impairs identification of target stimuli ~2 seconds later. Moreover, the visual deficit relates to the disruption of anticipatory (pre-stimulus) alpha desynchronization and its topography in parieto-occipital cortex. After right IPS stimulation, the degree to which alpha desynchronization is suppressed predicts the speed of visual identification. These results demonstrate the causal role of posterior parietal cortex in the control of visuo-spatial attention exerted through the synchronization of visual neurons.
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