Cortical asymmetries of the human somatosensory hand representation in right- and left-handers

Hemispheric asymmetry is known for higher brain functions like language and attention. We tested whether such an asymmetry also exists in the represen tation of elementary sensory functions. Magnetic source imaging was used to compare the cortical somatosensory hand representation in seven right- and five left-handed individuals. In all right-handers the representation of t he dominant hand was larger than the contralateral one in the corresponding hemispheres. In contrast, only two out of five left-handers revealed a lar ger representation of the dominant left hand compared to the right one. In agreement with previous findings on the lateralization of language and atte ntion, there is a strong correlation between handedness and the extent of t he cortical hand representation in right-, but not in left-handers. We conc lude that a profound functional hemispheric asymmetry also exists in primar y sensory cortices. (C) 1999 Elsevier Science Ireland Ltd. All rights reser ved.