Poster D52, Monday, March 27, 8:00 – 10:00 am, Pacific Concourse
The effects of individual variations in Contrast Sensitivity on Working Memory: An ERP study.
Cristina Filannino1, Elliot Freeman1, Andrew Parton2, Corinna Haenschel1; 1City, University of London, 2Brunel University London
Few studies have examined the basic visual processes underlying encoding into working memory (WM). Here we investigate how individual variations in sensitivity to contrast affect WM. More specifically, we utilised stimuli for which the perceived contrast depends on the strength of lateral inhibitory activity in early visual areas as indexed by both behaviour and ERP responses. In an initial contrast matching task (CM), twenty participants confirmed that a central target grating appeared to have less contrast in the context of a co-oriented surround compared to an orthogonally-oriented surround. A further contrast detection task was then used to set individual supra-threshold contrast levels in the main WM match-to-sample task. On each trial of that task, participants viewed one to three sequentially presented oriented gratings surrounded by either orthogonal or parallel band-pass filtered noise. They then judged whether a subsequent probe (without a surround) matched any of the targets. Performance on CM and WM tasks correlated significantly: greater co-oriented surround suppression of perceived contrast predicted better match-to-sample accuracy. WM performance based on simple visibility of the target would have predicted the opposite relationship. During WM encoding, the P2 ERP component was significantly higher in the orthogonal condition. Furthermore, during retrieval P1 component and slow-wave activity were modulated by WM load. This slow-wave activity correlated with the CM surround-orientation effect on perceived contrast, even though the evoking probe stimulus had no surround. In summary, fundamental contrast processing mechanisms affect WM processing. This is reflected in both visual and higher cognitive ERP components.
Topic Area: EXECUTIVE PROCESSES: Working memory