(A) Example connected pair showing the stimulation pulses (top) and action potentials (middle) in the presynaptic cell; monosynaptically evoked EPSPs (bottom) in the postsynaptic cell. Traces represent every fifth sweep from the 50 Hz protocol used to measure recovery from STP at a delay of 250 ms. (B) Following repeated stimulation, the response to the first spike in each train of current pulsess was used for EPSP feature analysis. Spikes are shown aligned to the pulse time to illustrate jitter in spike timing. Spike time was defined as the region of maximum dV/dt in the spike trace, as shown in the raster plot corresponding to spike timing of individual spikes. Below, EPSPs are aligned to the spike time prior to fitting the average EPSP (see Equation 1; individual sweeps in grey, average response in blue, fit shown in red). The rise time was calculated as the interval between 20% and 80% of the peak amplitude of the fit. Spike-aligned EPSPs were deconvolved (see Equation 2, shown in figure), and the peak amplitudes of the deconvolved traces were used to measure changes in response amplitude of the course of a spike train. Responses were corrected to the baseline by subtracting the mode of the region between 10 ms and 50 µs prior to stimulus onset (baseline window). Responses were measured as the peak response during a 4 ms window beginning 1 ms after the spike time (response window shown is aligned to mean spike time). (C–G) Subsets of total connectivity data were used in subsequent analysis. Flowchart shows sweep (green) and connection (grey) level inclusion criteria for data included in each figure. See Table 1 for total number of cells in each criterion.