Spatial and non-spatial aspects of neglect

Global statistical regularities modulate the speed of visual search in patients with focal attentional deficits

“…The present results suggest that the stability of such representations facilitates patients in searching for targets in the neglected regions, where attentional resources are compromised. Our findings also extend previous results suggesting patients with attentional deficits are sensitive to the background statistics of visual displays (Demeyere et al, 2008; Leib et al, 2012) by demonstrating that the stability of these statistics can facilitate visual search in regions where patients have difficulty perceiving individual objects. Our results are in-line with a previous report by Saevarsson et al (2008) that the availability of a stable spatial context improved patients’ performance in neglected regions in a visual search task.…”

“…However, regardless of whether statistics were only represented in the spared regions, stability facilitated search in the neglected regions where focal attentional resources were compromised in a different manner than search in the spared regions. Findings from previous investigations of statistical processing in neglect patients (outlined in the Introduction) showing that statistical properties in the neglected visual field affect statistical processing in the spared regions (e.g., Pavlovskaya et al, 2010; Leib et al, 2012), and proposals that summary representations are calculated based on weighted-averages of items with the sets (e.g., De Fockert and Marchant, 2008; Alvarez, 2011) also support the idea that the statistics of the entire visual display, and not only statistics in patients’ spared regions, were driving the observed effects on search performance.…”

“…This differential effect of stability in neglected and spared regions may be explained by patients becoming aware of their specific deficits and developing different strategies, both as natural coping mechanisms and through typical therapeutic methods and repeated testing via typical tasks (e.g., cancelation/search) used to assess neglect. For example, patients may have learned to spread attention more diffusely over the entire display, making global statistical properties more available (e.g., Leib et al, 2012). They may also have learned to rely more heavily on focused attention in the spared regions where they were able to perceive individual objects well, and distributed attention over the neglected regions where they were not.…”

“…Most recently, Leib et al (2012) investigated whether neglect patients were equally sensitive to the average properties of elements in both neglected and spared regions. Patients were presented with a single circle target and subsequently instructed to search for the same target in display of multiple circles on one side of the screen, ignoring a set of distractor triangles located on the other side of the screen.…”

“…Findings from studies of both neurotypical observers (e.g., Chun and Jiang, 1998) and neurological patients (Saevarsson et al, 2008) that a repeated spatial relationship between a target and a given context can facilitate visual search and that global set properties are perceptually encoded (e.g., Leib et al, 2012) raise the possibility that the mere repetition of global statistical regularities may similarly facilitate search, regardless of the spatial relationship between the target and the contextual elements. Neglect patients serve as an interesting test group for studying the possible effects of global visual processing in the near absence of focused attention (or at the very least, under conditions in which focused attentional resources are severely compromised in the neglected regions).…”