Individual MLI depolarization mimics the optically induced excitation–inhibition sequence. (A1) Sample voltage trace from a tight-seal whole cell recording of an MLI maintained in current-clamp configuration. 18 pA steady current was injected to set the basal firing rate at around 6 Hz. A current pulse (25 pA amplitude, 1 s duration; timing indicated in upper trace) increased the firing rate to 50 Hz. The increase was followed by a silent period upon the end of the stimulation. (A2) Temporal evolution of the peak spike amplitude (upper trace) and of the minimum of the AHP (bottom trace) starting 5 s before the stimulation and ending with the stimulation. The red lines correspond to the mean values for pre-stimulation (peak: −13.8 mV, AHP: −76.1 mV) and during stimulation (peak: −12.2 mV, AHP: −73.6 mV). (A3) PSTH from five repetitions. (B1) Voltage recording from the same MLI, in response to a 1 s long optical stimulation. (B2) Temporal evolution of peak spike amplitude and AHP minimum, as described in A2. Mean maximum and minimum AP values are shown for pre-stimulation (peak: −12 mV, AHP: −75.6 mV) and during stimulation (peak: −12.4 mV, AHP: −73.7 mV). (B3) PSTH from five repetitions. (C) Pooled data on spike rates from five MLIs, before the step of current injection (Pre) during the current step (I step) and during the 1 s following the stimulation (Post; cell injected with the same current as in the Pre period). For each MLI, three to seven repetitions were performed. (D) Ratios for the increase in spike rate during the current step (left) and for the decrease observed after the current step.