Differential consequences of orienting attention in parallel and serial search: an ERP study.

Previous research has linked attentional effects (such as inhibition of return; IOR) to serial visual search. We investigated different modes of visual search (serial vs. parallel) and demonstrated that the attentional set induced by the type of search greatly influences these attentional effects. IOR was linked to serial search while facilitation followed parallel search. Event related potentials and LORETA source localization data demonstrated that facilitation was associated with a single component, localized in the cuneus and precuneus, while IOR was related to three different components, involving the superior parietal lobe (at around 200 ms), the anterior cingulate cortex and bilateral medial frontal gyrus (240 ms), and the bilateral superior temporal gyrus, supramarginal gyrus and inferior parietal gyrus (280 ms). Our results are consistent with the notion that attentional set determines spatial orienting and with previous studies proposing that IOR is not observed in all previously attended locations.