Abstract
In visual search, participants are required to detect the presence or absence of a pre-defined target. In search for pop-out targets, Müller, Heller and Ziegler (1995) found facilitated detection (i.e. faster reaction times [RTs]) when the target defining dimension remained the same compared to when it changed across trials (i.e. slower RTs). We tested the longevity of dimensional costs and benefits in search for a pop-out target in patients who have suffered from brain damage to further investigate those areas critically involved in the carry-over effects. Participants had to search for targets defined by either its color (red or blue) or orientation (right- or left-tilted) dimension. On consecutive trials, the target dimension stayed the same or changed. We categorized patients according to whether they showed an effect of dimensional change on search or not. Using voxel-based morphometry (Asburner and Friston, 2000) we compared the group of patients with dimensional effects (N = 16) with the group of patients without dimensional effects (N = 9). While controlling for spatial deficits of the patients (either to left or right; neglect plus visual extinction), whole brain voxel-wise analysis showed that damage to grey matter within the right inferior parietal lobule (the angular and supramarginal gyri and partially involving the intraparietal sulcus [IPS]) was correlated with reduced dimensional effects (cluster level corrected, p = 0.0001). Pollmann et al. (2006) proposed that several core anatomical structures were activated when dimensional changes occur in search, including the regions found critical in our data, and he linked the regions to the processes involved in attention shifting from one dimension to another. Our data suggest that these regions of parietal cortex are necessary to attention shifting in the context of visual dimensional change.
Meeting abstract presented at VSS 2012