Moreover , significant differences in the change values of map size ( 7.0 [ 7.9 ] for the experimental group vs. -1.7 [ 2.9 ] for the control group , P = 0.03 ) and mean ( SD ) motor evoked potentials ( 0.4 [ 8.9 ] mV for the experimental group vs. -0.1 [ 0.1 ] mV for the control group , P = 0.03 ) were found .