Fig. 8.

Effect of DCS on CA1 population spike evoked by antidromic stimulation of CA1 neurons depends on the relative orientation of the DC current vector and the vector of the (AP) propagation. The diagram shows amplitudes of normalized amplitudes from Figs. 6D and 7D before DCS in gray (100%) and during 100- and 200-μA DCS as red circles and blue squares, respectively. The direction of the AP vector is shown as the red arrow in the origin (corresponding to 60%), and the directions of the DC current correspond to the back arrows at the ends of the axes (with ticks spaced at 10%). Filled circles and squares correspond to statistically significant effects on the amplitude. Open symbols correspond to nonsignificant variations. *P < 0.05 between the effects of 100-μA DC parallel and antiparallel to the AP propagation vector. Note that DCS always inhibits fEPSP when the vector projection of the AP propagation in the direction of the DC current is positive.