Stimulation site and electrophysiological properties of subicular regular-firing cells in hippocampal formation.

a) Schematic illustration of hippocampal formation with stimulating and recording electrodes in SUB. Arrows mark excitatory connections, a flash marks the stimulation site in the alveus, between CA1 and SUB. Hippocampal areas: DG  =  dentate gyrus, CA1, CA3, SUB  =  subiculum, EC  =  entorhinal cortex, sc  =  schaffer collaterals. b) Voltage responses upon depolarizing and hyperpolarizing current pulses. Cells discharged with single spikes, each followed by a fast afterhyperpolarization (▴). Scale bars: 25 mV, 50 ms. c) Expanded time scale. Initial spike frequencies and afterhyperpolarization. Scale bars: 25 mV, 10 ms. d) Sag (▴) and rebound potentials (▾) upon hyperpolarizing current pulses. Scale bars: 25 mV, 50 ms. e) Exemplary voltage response upon hyperpolarizing current pulse, illustrating calculation of sag and rebound potentials (see Methods).