EMG as a key tool to assess motor lateralization and hand reaction time asymmetries

Inconsistent and conflicting results about hand reaction time (RT) asymmetries have led to controversies over lateralization and hemispheric specialization for visuomotor transformations. In this paper, we propose a methodological solution to separate the central and peripheral processes that may be differently involved in simple visuomotor asymmetries. We provide empirical data from a simple RT task that suggests that fractionating RT into motor and premotor components with respect to a change in the electromyographic activity is necessary to disentangle motor and premotor lateralization patterns. These results call for a refinement of classical studies of visuomotor transformations using electrophysiological correlates of embedded but unrelated asymmetries rather than overt psychophysical measurements alone.