TMS of the right angular gyrus modulates priming of pop-out in visual search: combined TMS-ERP evidence

During priming of pop-out, performance at discriminating a pop-out feature target in visual search is affected by whether the target on the previous trial was defined by the same feature as on the upcoming trial. Recent studies suggest that priming of pop-out relies on attentional processes. With the use of simultaneous, combined transcranial magnetic stimulation and event-related potential recording (TMS-ERP), we tested for any critical role of the right angular gyrus (rANG) and left and right frontal eye fields (FEFs)—key attentional sites—in modulating both performance and the ERPs evoked by such visual events. Intertrial TMS trains were applied while participants discriminated the orientation of a color pop-out element in a visual search array. rANG TMS disrupted priming of pop-out, reducing reaction time costs on switch trials and speeding responses when the color of the pop-out target switched. rANG TMS caused a negativity in the ERP elicited in response to the visual stimulus array, starting 210 ms after stimulus onset. Both behavioral and ERP effects were apparent only after rANG TMS, on switch trials, and when the target in the visual search array was presented in the left visual field, with no effects after left or right FEF TMS. These results provide evidence for an attentional reorienting mechanism, which originates in the rANG and is modulated by the implicit memory of the previous trial. The rANG plays a causal role on switch trials during priming of pop-out by interacting with visual processing, particularly in the ipsilateral hemisphere representing the contralateral hemifield.