Somatosensory lateralization in the newborn brain.

Since the onset and early postnatal development of hemispheric lateralization in the human brain are unknown, we studied cortical activation induced by passive extension and flexion of the hand in neonates using functional magnetic resonance imaging (fMRI). In contrast to that seen in older age groups, somatosensory areas in the pre- and postcentral gyri of the neonate showed no significant hemispheric lateralization at term. Instead, our findings from independent left- and right-hand experiments suggest the presence of an emerging trend of contralateral lateralization of the somatosensory system at around term.