A Prismatic view of the hand: The influence of verbal and tactile feedback on visuotactile predictions.

Abstract

We interact all the time with our environment. In order to do this efficiently we persistently make visuotactile predictions. However, certain patient groups, such as patients with unilateral neglect, show deficits in their interaction with their environment. Unilateral neglect is a disorder in which patients are unaware of the contralesional space (Danckert & Ferber, 2006). One technique often used in rehabilitation programs for unilateral neglect is prism adaptation. Prism adaptation could be of beneficial influence on neglect symptoms. What stands in the way of usage is that the actual method of reaching prism adaptation (with motor execution or motor imagery) may pose a problem for neglect patients, because of the usage of movements. This because patients with severe unilateral neglect have problems during movement initiation and execution. In this study healthy subjects were used to assess if it is possible to obtain a prism adaptation without the usage of movement. When in real life visuotactile predictions are made, feedback from different sensory modalities will follow, so in this research where assessing the influence of different types of feedback (no-, verbal- and tactile-feedback). In the current study, participants had to make visuotactile predictions before, during and after prism exposure. After each block of visuotactile predictions the participants had to indicate their body-midline, to assess proprioception. The results show that prism adaptation occurred in all three conditions (no-, verbal- and tactile-feedback) during the visuotactile prediction task, as is revealed by an after-effect. The observation of an after-effect in the “no-feedback” condition indicates that the participants must have had some kind feedback. Therefore the “no-feedback” condition was excluded from further analyses. Also an after-effect is shown in the proprioception task. Both after-effects are not the result of different amounts or various sizes of wrong given answers. Hereby can we conclude that it is possible to obtain a prism adaptation without the usage of movement, for both types of feedback (verbal and tactile).