Figure 2. Dendrites of the DSGC are electrotonically isolated.

(a, b, c) In a passive model without voltage-gated channels, a weak synaptic input (50pS, 100ms) excited a point in the dendritic tree, and the amplitude of the PSP spreading across the dendritic tree is shown in color, 50 ms after the onset of the stimulus. (d) Plot of input resistance (R_in) vs. distance from soma for the morphologies shown above (green triangle = a, black square = b, blue circle = c). (e) Estimated local average space constant (see Methods) lambda_est versus distance from soma for the three morphologies. Symbols and colors same as in (d). The black line is unity (soma distance = lambda _est). (f) Amplitude of subthreshold PSPs from single synapses across an active dendritic tree for the morphology shown in (c) at the soma (black circles) and in the dendrites (gray circles). Dendritic membrane and axial resistivities were uniform, with Rm = 40,000Ω·cm² and Ri = 200Ω·cm (see Methods). For reference, these values produce lambda = 500 µm in a passive infinite cable of diameter 0.5µm. Lamba _est was smaller than this reference value because many dendrites in our model had a diameter less than 0.5um, and impedance mismatches and branch points between cables further contributed to substantial attenuation of voltage spread.