Attentional control during the transient updating of cue information

The goal of the present study was to investigate the neural correlates of top-down control of switching behavior in humans and to contrast them to those observed during switching behavior guided by bottom-up mechanisms. In the main experimental condition (color-cue), which was guided by top-down control, a central cue indicated the color of a peripheral grating on which the subject performed an orientation judgment. For switch trials, the color of the cue on the current trial was different from the color on the previous trial, For non-switch trials, the color of the cue on the cur-rent trial was the same as the color in the preceding trial. During a control condition (pop-out), which was guided by bottom-up saliency, the target grating was defined by color contrast; again both switch and non-switch trials occurred. We observed stronger evoked responses during the color-cue task relative to the pop-out task in the inferior parietal lobule (IPL), frontal eye field (FEF), middle frontal gyrus (MFG), and inferior frontal gyrus (IFG). The contrast of switch vs. non-switch trials revealed activations in regions that were engaged when there was a change in the identity of the target. Collectively, switch trials evoked stronger responses relative to non-switch trials in fronto-parietal regions that appeared to be left lateralized, including left intraparietal sulcus (IPS) and left MFG/IFG. Task by trial type interactions (switch>non-switch during color-cue relative to pop-out) were observed in several fronto-parietal regions, including IPS, FEF, MFG and IFG, in addition to regions in visual cortex. Our findings suggest that, within the fronto-parietal attentional network, the IPS and MFG/IFG appear to be most heavily involved in attentive cue updating. Furthermore, several visual regions engaged by oriented gratings were strongly affected by cue updating, raising the possibility that they were the recipient of top-down signals that were generated when cue information was updated. (C) 2008 Elsevier B.V. All rights reserved.