Fig. 1

Schematic diagram of electrode locations, electrode geometry and waveforms of evoked potentials. a The recording array in the hippocampal CA1 region, and stimulation electrodes for orthodromic activation and antidromic activation in the Schaffer collaterals and alveus fibers, respectively. b The tip structure of the concentric bipolar stimulation electrodes. c Examples of orthodromically evoked population spike (OPS) evoked by a single monophasic and biphasic pulse. d Comparison of mean amplitudes of baseline OPS induced by single pulses of monophase (n = 5) and biphase (n = 6) with a same current intensity