Figure 2.
Steady-state electrical properties of TC neuron dendrites. A, Overlay of two-photon fluorescence and infrared scanning gradient contrast images of a dLGN TC neuron showing the location of a somatic (red) and a dendritic (red) recording pipette. Inset, Schematic of the recording configuration illustrating the neuron recorded from (TC) and the placement of recording electrodes. This schematic is used throughout to indicate that the illustrated data are drawn from TC neuron recordings. B, ΔVmSS (blue) and ΔVmDS (red) evoked by 500 ms somatic current injections between −160 and +200 pA. Inset, Mean somatic and dendritic resting membrane potentials. C, ΔVmSD and ΔVmDD evoked by 500 ms dendritic current injections between −100 and +80 pA. D, Schematic illustrating the two-port T-circuit model incorporating the axial impedances ZA and ZB and the common transfer impedance ZC used to describe dendritic electrical conduction. E, Normalized steady-state voltage transfer in the S→D (red) and D→S (blue) directions. Solid colored lines, Decaying exponential fits to the experimental data; gray lines, voltage transfer in each direction from four model dendrites. F, Somatodendritic input resistance (RN) profile. Red circles, Somatic and dendritic RN for individual neurons; blue square, mean somatic RN; gray lines, RN profiles of model dendrites. G, Transfer resistance (RC) versus distance from soma calculated for S→D (red) and D→S (blue) directions. Gray lines, S→D RC for model dendrites. H, ΔVmS and ΔVmD evoked by current injection at the reciprocal recording site. The dashed black line indicates unity. I, Normalized dendrite to soma current transmission versus distance from soma. Solid red line, Decaying exponential fit to the data.