Figure 3.

Conductance estimation. A, Top, Levels of current injection through the pipette that were paired with presentations of visual stimuli and used for conductance estimation. Bottom, average ± 95% confidence interval of 12 trials at each of the four levels of current injection. Stimulus on a time of 128 ms shown as the bar under the traces. The time points indicated correspond with points used for the I–V plot in B and are shown in C. B, Linear I–V relationship at rest (open circles, dashed line is linear fit, error bars show 1 SD) and at the time point indicated in A (filled circles, solid line). The slope of each line gives the R_in, and the inverse yields total conductance gT. During the synaptic response, gSyn is calculated as gT(t) − gT(rest). The intersection of the two lines gives the synaptic reversal potential (V_rev) for that time in the response. C–E, G, V_rev (black), gSyn (gray), excitatory conductance (gE, red), and inhibitory conductance (gI, blue) as a function of time throughout the synaptic response to the visual stimulus. C, Vertical line indicates the filled circle time point shown in A and B. D, Analysis using only trials without action potentials. E, An excitatory bar stimulus in a cell recorded with QX-314 in the recording pipette (dark bar in position 7, OFF subregion, of the cell in Fig. 4). F, Time point-by-time point comparison of recorded and reconstructed V_m shows excellent agreement across many levels of current injection, with a root mean square (RMS) error of 1.95 mV. G, Left, A stimulus of dark pixels (outlined in dashed line) was hand plotted on-line to remain well inside the OFF subregion of the cell in A–D. Right, V_rev, gSyn, gE, and gI in response to this stimulus.