Figure 3.

Figure 3.

EPSC events within the same amplitude bin predominantly reflect multiple neuronal inputs. A, An example cell with four stable and discrete amplitude bins (colored by bin). B, Example EPSC traces demonstrate events that co-occur within 1 ms. Event pairs are either within-bin (left) or across-bin (right). C, To estimate an upper limit on the expected refractory period violations because of bin overlap, EPSC amplitude distributions were modeled as a sum of individual Gaussians (dashed colored lines). D, Average waveforms from each EPSC bin (±SD; n = 6497, 2581, 2000, and 1011 events/bin). E, Autocorrelograms show structure of interevent intervals within an EPSC bin; note peaks near zero in bins 1 and 3, a nonzero valley for bin 2, and a true valley for the high-amplitude bin 4. F, Waveforms from EPSC pairs within bin 3 with latencies <1 ms (n = 29 event pairs). The large jitter between peaks is inconsistent with the expected profile of an electrochemical synapse. G, Observed within-bin refractory period violations as a function of bin amplitude for bins assigned as having nonunitary (blue) or unitary (brown) origin. The probability distribution of bin amplitudes is shown above. H, I, EPSC event timing from two example nonunitary (H) or unitary (I) bins aligned to one oscillation of lateral translation. EPSCs within a single bin can exhibit simple tuning with a single peak in EPSC rate (top) or can have complex tuning with multiple peaks in EPSC rate during oscillation (bottom). Asterisks indicate EPSC tuning peaks. J, Histogram of the number of EPSC rate peaks per amplitude bin during translation (maximum per bin across lateral and fore–aft stimuli) for nonunitary and unitary EPSC bins.