Abstract
Previous research has demonstrated that rightward shifting prismatic lenses can reduce symptoms of left spatial neglect in patients with right brain damage. This reduction in left neglect symptoms is thought to be related to the fact that rightward shifting prisms require the patient to adjust their movements leftward (i.e., towards the neglected field) to compensate for the rightward visual shift. Similarly, previous studies in healthy individuals have shown that adaptation to leftward shifting prisms, which induce a rightward adjustment in movements, can create "neglect-like" patterns of behaviour (i.e., a subtle rightward attentional bias) on tests of spatial attention and spatial biases. Critically, previous studies of prism adaptation in patients with neglect, and healthy individuals, have only examined the effects of a single magnitude of visual shift (typically 10°) on test performance. This leaves open the question as to whether or not larger magnitudes of visual shift will induce larger effects on tests of attention and spatial biases. To examine this question in healthy individuals (n=30) we compared the effects of 8.5° and 17° leftward shifting prisms on a manual line bisection task (i.e., bisecting a line in half using a pen), and a perceptual equivalent of the line bisection task (i.e., judging whether a bisection marker on a line is closer to the left or right end of the line). The results indicated that, for the manual line bisection task, there was a larger rightward shift in bisection performance following adaptation to 17° compared to 8.5° leftward shifting prisms. However, for the perceptual version of the bisection task, participants demonstrated an equivalent rightward shift in perceived midpoint regardless of the magnitude of leftward prism shift. These data are consistent with recent studies indicating that prism adaptation may have differential effects on motor compared to perceptual components of neglect.
Meeting abstract presented at VSS 2014