Abstract
A short period of prism adaptation (PA) has been shown to reduce neglect symptoms, but evidence suggests this effect might be restricted to visually guided actions, leaving perception unaffected. One explanation for this dissociation potentially lies in the method used to promote adaptation. The majority of studies have used concurrent exposure, a technique that promotes a change in felt arm position (proprioceptive straight ahead, PSA). Few studies have used terminal exposure, a technique that promotes a shift in perceived visual straight ahead (VSA). Thus, the observed positive effects of PA may appear to be primarily action based because studies have adopted an exposure procedure that promotes a change in felt arm position. Here we compare the effects of the two exposure types on a perceptual and a manual line bisection task in healthy young adults. Before and after six minutes of exposure to leftward displacing prisms we took two measures of perceived straight ahead (PSA and VSA) and administered two line bisection tasks (a manual task and a perceptual landmark task). During the exposure period participants made pointing movements while the view of their pointing arm was either (i) restricted to the final part of the pointing movement (terminal exposure) or (ii) restricted to the second half of the pointing movement (concurrent exposure). In line with previous research, terminal exposure produced a larger shift in VSA; concurrent exposure produced a larger shift in PSA. Change in manual bisection from pre to post exposure was found to be significantly greater after concurrent exposure. In contrast, a shift in performance on the perceptual landmark task was found only after terminal exposure. Taken together, our results shed light on the underlying mechanisms of prism-induced neglect recovery, demonstrating that task performance depends on the type of PA.
Meeting abstract presented at VSS 2012