In our three-year study, 40 men with SCI will be recruited each year, 40 age-matched men as control. In the first year study, FDG-PET will be used to assess the cerebral metabolism, then the glucose metabolic rate of cerebrum and spinal cord will be analyzed. The mechanism of cerebral adaptation after SCI may be clarified. 13N-NH3 will be used in the second year to evaluate the cerebral blood flow in the period of attempted and true action, then their difference will be analyzed by statistical parametric mapping. The picture of activated brain area will be compared between study and control group to investigate the reorganization of cerebral cortex after SCI. In the third year, we will use 18F-FDOPA to evaluate the brain presynaptic dopaminergic function among SCI and control group. Thus, we will delineate the effect of SCI on cerebral function by PET.