Abstract: Objective To explore the activation of the primary somatosensory cortex (S_Ⅰ) and secondary somatosensory cortex (S_Ⅱ) undermild and moderate pain. Methods 7 healthy right-handed volunteers accepted electrostimulation of 1 and 2 times pain threshold respectively.The severity of pain was determined with the Visual Analogue Score (VAS), and they received functional magnetic resonance imaging(fMRI) simultaneously. Results 1 and 2 times pain threshold electrical stimulation caused mild and moderate pain respectively. Bothmild and moderate pain activated contralateral S_Ⅰ similarly, and bilateral S_Ⅱ with pain intensity. Conclusion S_Ⅰ and S_Ⅱ respond to the mildand moderate pain in different ways.

Key words: pain, electrostimulation, somatosensory cortex, functional magnetic resonance imaging