M20 amplitudes in left and right hemisphere in males are 23.6+ 11.2nAm , 25.4+ 11.2nAm in males and 25.8 + 10.5nAm , 27.6+7.8nAm in females. M20 source strength was not different in the isolateral hemisphere between males and females(P>0.05).

• M20左、右半球波幅男性23.；6±11