Figure 5.

Confirmation of Optically Identified Connections

(A–E) Confirmations of connections from 5 different mapping experiments. Left panels: 5 repeats of whole-cell current recordings of the postsynaptic neuron (N1) during optical stimulation (red area) at the z position of the targeted soma during a mapping experiment. Middle panels: simultaneous voltage recordings of the cell identified online as putatively synaptically connected (N2) and current recording of the postsynaptic cell (N1). APs were triggered by the current injection of either single pulses (1 nA, 2 ms, 1 s interstimulation time, except for E where we injected 500 pA for 10 ms) or trains of 4 APs (1 nA, 2 ms, 15 ms interstimulation time and 5 s between trains). Averaged number of trials: 50, 24, 18, 8, 17 in A, B, C, D, and E respectively. Right panels: overlays of sum z projections from stacked images of each mapping experiment, displaying in white EYFP fluorescence and in red fluorescence of Alexa 594 from internal solution, filling the patched neurons. White arrowheads indicate N1 and red arrows indicate N2. Scale bar, 50 μm; pia is located at the top. Note that A corresponds to target #97 from Figure 3.