Purchase this article with an account.
Viola Störmer, Patrick Cavanagh, George Alvarez; The profile of multifocal attention: surround-suppression between and within hemifields. Journal of Vision 2013;13(9):1283. doi: 10.1167/13.9.1283.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Keeping track of multiple moving objects is an important aspect of visual cognition. Previous behavioral studies have shown that attention can select moving targets independently in the left and right visual fields (Alvarez & Cavanagh, 2005). Recent research indicates that one critical aspect of this hemifield effect is the requirement to spatially filter task-irrelevant information surrounding the targets (Alvarez, Gill, & Cavanagh, 2012). Here we tested whether there are differences in the efficiency of surround-suppression when attention is allocated to targets within a visual hemifield or between visual hemifields. We used an attentive tracking task that requires the continuous selection of one item from a pair of targets that orbited around a common center. Rotation speed thresholds for 80% accuracy were obtained for each individual and condition prior to the experiment. Threshold speeds for between-hemifield tracking were higher (better performance) relative to within-hemifield tracking. During the main experiment we recorded electrophysiological responses (ERPs) while observers tracked one target (unifocal), two targets that were presented between hemifields (multifocal bilateral), or two targets that were presented within a hemifield (multifocal unilateral). To directly assess surround suppression, we presented probe stimuli at a fixed location (within the top left quadrant) at a fixed distance from the target. We observed that the response to the probe was suppressed when participants tracked two targets in separate hemifields (left and right) compared to when participants tracked two targets within one hemifield. These findings show that surround-suppression operates more effectively during bilateral tracking relative to unilateral tracking. These differences in suppressive surrounds suggest that attention can be more sharply focused around each target when targets are in separate hemifields rather than in the same hemifield and that this is a likely mechanism contributing to the behaviorally observed hemifield effects in many spatial attention tasks.
Meeting abstract presented at VSS 2013
This PDF is available to Subscribers Only