[Functional relationship between the cerebrum and cerebellum in normal subjects]

To determine whether a functional relationship between the cerebrum and cerebellum exists in normal subjects, the correlation between asymmetry in cerebral blood flow and asymmetry in cerebellar blood flow was investigated. Twenty-one healthy right-handed subjects were studied using SPECT with N-isopropyl-p-(123I)iodoamphetamine while in a resting state. The asymmetry index (AI) for both the cerebral and cerebellar hemisphere was calculated as follows. AI = R - L/R + L/200 (%) (R: right side, L: left side). A negative correlation was found between AI in the cerebellum and AI in cerebrum. Especially, AI in cerebellar hemisphere was significantly correlated with AIs in the upper frontal cortex (r = -0.58, p less than 0.01), middle frontal cortex (r = -0.55, p less than 0.02), lower frontal cortex (r = -0.49, p less than 0.05), and mean cerebral hemisphere (r = -0.52, p less than 0.02). These results suggest the existence of a functional relationship between the cerebral hemisphere and the contralateral cerebellar hemisphere in the resting state of normal subjects. We strongly suspect that the frontal cortex exert an influence on the function in the contralateral cerebellum, probably due to a transneuronal mechanism, mainly through the corticopontocerebellar pathway.