PET STUDY OF THE LOCALIZATION AND LATERALITY OF LINGUAL SOMATOSENSORYPROCESSING IN HUMANS

Regional cerebral blood flow (rCBF) was measured using positron emissi on tomography (PET) during four tasks in right-handed volunteers with eyes closed: resting, protruding the tongue, stroking the left side of the protruding tongue, and stroking the right side of the protruding tongue. The primary somatosensory tongue representation (SI) mapped to the contralateral central sulcus (Brodmann (BA) 3/4) at approximately 28 mm above the intercommissural plane. Of note, stimulation of the l eft side of the tongue produced also an ipsilateral S1 response. Analy sis of variance (ANOVA) of rCBF at S1 across all four conditions yield ed only a significant effect for tongue stimulation, with no effect of laterality; the usually large asymmetries (contralateral much greater than ipsilateral) in S1 did not surface. We hypothesize that this aty pical activation pattern arises from the tongue's specialization for l anguage. (C) 1997 Elsevier Science Ireland Ltd.