Figure 5C plots the median of the amplitude distributions against the distance from the inversion (n=105 penetrations). In general, the amplitude of the P30 and its decay rate decreased with distance. However, the peak amplitude stayed positive and significantly different from zero (bootstrap two-tailed, p<0.05), all the way to the dorsal brain surface. These results are consistent with the forward solution of Poisson's equation, in which distribution of potential is proportional to the inverse of distance.
