Asymmetric somatosensory activation with right- vs left-hand stimulation: a positron emission tomographic study.

Metabolic activation of the right and left somatosensory cortices (SSC) in response to an active sensorimotor task (palpation and sorting of mah jongg tiles) was studied in 16 right-handed normal volunteers using positron emission tomography (PET) and a double-injection [18F]fluorodeoxyglucose strategy. In 8 subjects with right-hand stimulation, cerebral metabolic rate for glucose (CMRglc) in the contralateral SSC increased by 16.7 +/- 5.1% (mean +/- S.D.); the increase in the ipsilateral SSC was 4.8 +/- 3.2%. In contrast, in the 8 subjects with left-hand stimulation, the contralateral increase was 12.0 +/- 2.9% and the ipsilateral increase was 5.9 +/- 1.5%. Thus, contralateral SSC activation was significantly higher with stimulation of the right hand, while the ipsilateral/contralateral symmetry of activation was greater when the left hand was stimulated.