Vibratory stimulation increases and decreases the regional cerebral blood flow and oxidative metabolism: a positron emission tomography (PET) study.

The aim of this study was to examine the hypothesis, if the activation of some cerebral structures due to physiological stimulation is accompanied by deactivations of other structures elsewhere in the brain. A vibratory stimulus was applied to the right hand palm of healthy volunteers and the regional cerebral blood flow (rCBF) and regional cerebral oxygen metabolism (rCMRO2) were measured with positron emission tomography (PET). Regional analysis and voxel-by-voxel plots indicated that the stimulation induced increases and decreases of the rCBF were coupled to increases and decreases of the rCMRO2. The increases were localized in the left primary somatosensory area (SI), the left secondary somatosensory area (SII), the left retroinsular field (RI), the left anterior parietal cortex, the left primary motor area (MI), and the left supplementary motor area (SMA). The decreases occurred bilaterally in the superior parietal cortex, in paralimbic association areas, and the left globus pallidus. The increases and decreases of the rCBF and rCMRO2 were balanced in such a way that the mean global CBF and CMRO2 did not change compared with rest. We conclude that the decreases of the cerebral oxidative metabolism indicated regional depressions of synaptic activity.