Brain correlates of hand dominance: the association between peripheral and cerebral asymmetries revisited

Measures reflecting central processing of somatosensory stimulation were recorded in left- and in right-handed subjects in order to evaluate differences between the two handedness groups in the vertical, rather than lateral, axis of processing. Somatosensory evoked potentials were recorded in left- and right-handers following electrical stimulation of the median nerve at the wrist. The relative vertical balance of processing was probed by comparing the amplitudes of the underlying activity in early evoked potentials, presumably originating subcortically, with later, cortically originating potentials. Central conduction time (CCT) of the sensory volleys was also recorded. The data revealed higher amplitude ratios (ARs) between subcortical and cortical potentials, as well as shorter CCTs, in left-handers. These results demonstrate that transmission differences between the handedness groups may occur early in central nervous system (CNS) conductance. The results are further discussed in light of evidence suggesting that stronger reliance on a subcortical mode of processing may underlie phenomenon of left-handedness.