Bilateral electrodermal and electrocortical activity in anticipation of sensorimotor tasks

The present study investigated the relationship between lateralized sensorimotor activation and lateralized elevation of electrodermal activity. Within a two-stimulus reaction time paradigm skin conductance responses (SCRs) were recorded from both hands, while subjects awaited and performed unilateral sensorimotor tasks. A tactile warning stimulus was applied 6 s prior to a tactile imperative stimulus either to the same or to the contralateral hand; the imperative stimulus was associated with a choice reaction time task. Task-dependent lateral asymmetry with larger skin conductance responses contralateral to the involved hemisphere indicated contralateral facilitatory processes rather than inhibition. This asymmetry disappeared with repeated stimulation (across trials). Only right-hand (left hemispheric) tasks proved to be sensitive to habituation. The asymmetry, recorded in slow brain potentials (SPs), assured that lateralized cortical processing was induced through the present experimental arrangement. The brain potentials specified the time course of lateralized processing, exhibiting larger late negative shifts at the precentral areas contralateral to the hand involved in the sensorimotor task and larger early negativity and a more pronounced positive evoked potential (late positive complex, LPC) contralateral to the hand stimulated by the tactile warning stimulus.