Abstract
We performed an experiment to determine the relative contributions of vision and proprioception to sensory adaptation to in-depth prismatic distortion. In-depth localization tests were performed before and after a 10-min period of left-hand pointing during which participants wore a pair of 5-PD base-out prisms that decreased apparent distance. Visual localization was measured using open-loop pointing to visual targets with the right hand. Proprioceptive localization was assessed using pointing to the left hand with the right hand, eyes closed. On average, subjects showed a significant 48-mm visual aftereffect (p<0.001) and a significant 6-mm proprioceptive aftereffect (p = 0.03). The visual aftereffect was significantly larger than the proprioceptive aftereffect (p<0.0001). Both aftereffects were in the expected direction. The mean relative contributions of vision and proprioception to sensory adaptation were 0.88 and 0.12 respectively. The optimal reliability-based calibration theory posits that adaptation is the largest in the least precise modality (Ghahramani et al., 1997). To determine whether these effects where consistent with this theory, the variances of pre-exposure localization for vision and proprioception were computed. The former (336 mm²) was significantly larger than the latter (54 mm²; p<0.0001). On average, the relative adaptation for vision (0.88) approximated the inverse of its relative reliability (0.81; p = 0.4). Overall, these results are consistent with the hypothesis that information from vision and proprioception is calibrated optimally to minimize estimated-position uncertainty (van Beers et al., 2002). Recent studies also suggest an influence of distorted visual feedback on visual reliability (van Beers et al., 2011). The neural correlates of in-depth coding for action and the corresponding visual and proprioceptive integration have been recently investigated, emphasizing the role of the posterior parietal cortex (Ferraina et al. 2009).
Meeting abstract presented at VSS 2012