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Prism adaptation ameliorates pseudoneglect by enhancing target processing in right hemispace

33.539, Sunday, 18-May, 8:30 am - 12:30 pm, Pavilion
Session: Attention: Divided

Elizabeth Nguyen1, Patrick T. Goodbourn1, Alex O. Holcombe1; 1School of Psychology, The University of Sydney, Australia

Line bisection and related tasks reveal a leftward attentional bias in healthy individuals (pseudoneglect). This bias is reduced by adaptation to visual experience of the scene shifted to the left. One theory is that a balance of activation between the two cerebral hemispheres—usually favoring the right hemisphere—is shifted after prism adaptation. Hence, an increase in processing on one side should be accompanied by a decrease on the other. Standard methods, such as line bisection, yield only relative measures of left–right performance; thus to test the theory, we instead derived independent, absolute measures of performance for left and right hemispace. Because it has been proposed that the two hemispheres are differentially involved in temporal processing, we also assessed whether adaptation affected temporal parameters of attentional selection. Goodbourn & Holcombe (VSS 2013) found a leftward bias, consistent with pseudoneglect, when two rapid serial visual presentation (RSVP) streams of letters were presented concurrently to the left and right of fixation. Target letters were cued simultaneously in both streams. While participants frequently reported simultaneous letters, efficacy of target selection was substantially higher for the left stream than for the right. In the present study, twelve observers completed the dual-RSVP task before and after adaptation to three types of prisms: left-shifting, right-shifting, and control. Consistent with previous pseudoneglect studies, no performance changes were found after right-shifting or control prism adaptation. In contrast, adaptation to left-shifting prisms reduced the leftward bias, selectively boosting right-stream performance: relevant letters were reported 9% more often after adaptation (P = 0.03). We found no accompanying decrement in left-stream performance. Temporal parameters (latency and precision) were unchanged for both sides. These findings suggest prism adaptation ameliorates biases not by rebalancing hemispheric activation, but rather by selectively enhancing processing of stimuli in the non-dominant right hemifield.

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