Motor output in a bimanual continuation-tapping task is independent of visual cues

Abstract

Presented are two studies examining the role of vision on motor output in the continuation-tapping paradigm (Stevens, 1886). The role of vision is measured by comparisons of motor performance under three visual feedback conditions: freeview, sagittal mirror and side mirror. The sagittal mirror condition provides the illusion achieved by the ‘virtual reality box’ (Ramachandran & Rogers-Ramachandran, 1996), often used in the treatment of phantom limb pain. The present study was prompted by work by Franz and Packman (2004), examining the same question by different experimental means. Their study is critiqued and results reinterpreted.

Experiment 1 followed a 3x2 repeated measures within subject design. Subjects tapped bimanually either in an asynchronous phase or a synchronous phase, under the three visual conditions. Subjects were provided with tactile and visual (real or virtual) feedback, but were deprived of auditory feedback and feedback regarding performance accuracy. We find that visual feedback has no effect on subsequent motor output for any of the dependent variables: all p>0.05. This contradicts results obtained by Franz and Packman (2004). There was a significant visual feedback*phase interaction; F=3.331, df (2,32), p=0.049, although overall results were considered null. Experiment 2 (2x1 repeated measures within subject design) removed tactile cues so as to amplify any effect of the visual cues. Experiment 2 also supported the null hypothesis, with no finding of an effect of vision on motor output. The present findings are discussed with reference to Franz and Packman’s study and directions for further study and also discussed.