Effects of stimulus intensity of electrical stimulation on functional MRI and MEG

To clarify the relationships between neuronal activity and the hemodynamic response, activations of the primary somatosensory cortex were studied using MEG (magnetoencephalogram) and fMRI (functional magnetic resonance imaging). Effects of the stimulus intensity of the electrical stimulation to the right thumb was investigated. The authors focused on the number of activated pixels, time courses of hemodynamic response obtained by fMRI and dipole moments of neuromagnetic activity. When the stimulus intensity increased to the pain feeling in the fMRI experiments, a number of activated pixels and signal power which was defined as the integration value of NMR signal were increase steeply, however, this inclination did not correspond to the neuronal activity