Abstract
Prism adaptation (PA) is both a perceptual-motor learning task as well as a promising rehabilitation tool for visuo-spatial neglect (VSN)—a spatial attention disorder often experienced after stroke resulting in slowed and/or inaccurate motor responses to contralesional targets. During PA, individuals are exposed to prism-induced shifts of the visual-field while performing a visuo-guided reaching task. After adaptation, with goggles removed, visuomotor responding is shifted to the opposite direction of that initially induced by the prisms. This visuomotor aftereffect has been used to study visuomotor learning and adaptation and has been applied clinically to reduce VSN severity by improving motor responding to stimuli in contralesional (usually left-sided) space. In order to optimize PA's use for VSN patients, it is important to elucidate the neural and cognitive processes that alter visuomotor function during PA. In the present study, healthy young adults underwent PA while event-related potentials (ERPs) were recorded at the termination of each reach (screen-touch), then binned according to accuracy (hit vs. miss) and phase of exposure block (early, middle, late). Results show that two ERP components were evoked by screen-touch: an error-related negativity (ERN), and a P300. The ERN was consistently evoked on miss trials during adaptation, while the P300 amplitude was largest during the early phase of adaptation for both hit and miss trials. This study provides evidence of two neural signals sensitive to visual feedback during PA that may sub-serve changes in visuomotor responding. Prior ERP research suggests that the ERN reflects an error processing system in medial-frontal cortex, while the P300 is suggested to reflect a system for context updating and learning. Future research is needed to elucidate the role of these ERP components in improving visuomotor responses among individuals with VSN.
Highlights
Exposure to prism goggles that cause a lateral shift in the visual field produces an initial direct effect on aiming during visuomotor tasks such as goal-directed reaching
Post-hoc analysis showed that movement time (MT) was significantly faster in the late phase compared to early phase, while neither differed significantly from middle
Because we hypothesized the P300 would be sensitive to learning over the course of the blocks, we first measured its amplitude according to phase rather than accuracy
Summary
Exposure to prism goggles that cause a lateral shift in the visual field produces an initial direct effect on aiming during visuomotor tasks such as goal-directed reaching. There is substantial evidence that when left VSN patients are exposed to a PA task, the leftward shifting after-effect provides benefits to their scanning and reaching performance (Rossetti et al, 1998; Frassinetti et al, 2002; Keane et al, 2006; Serino et al, 2006; Striemer and Danckert, 2007; Nys et al, 2008a; Sarri et al, 2008; Schindler et al, 2009; Bultitude and Rafal, 2010; Yang et al, 2013) benefits are not always seen (McIntosh et al, 2002; Dijkerman et al, 2003; Morris et al, 2004; Datié et al, 2006; Humphreys et al, 2006; Rousseaux et al, 2006; Nijboer et al, 2008; Nys et al, 2008b; Turton et al, 2010; Sarri et al, 2011)
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