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.