Figure 4. Effects of an intracellular Cl⁻gradient along the SAC dendrite and a delay in GABA channel closing on the modelled response of a SAC to a moving bar.

The simulation used both glutamate and GABA inputs to the SAC. The following four conditions were investigated. A, Cl⁻ was distributed passively across the membrane (E_Cl=E_GA=E_m). B, E_GA was constant and more positive than the membrane potential (–37 mV) along the entire dendritic length. C, there was a linear gradient of E_GA along the SAC dendrite (ranging from −37 mV in the body to −77 mV in both dendritic tips). D, the Cl⁻ gradient was as in C, and in addition, the GABA channels stayed open for 1.2 s more after the bar moved away from each segment. In A–D, R_i= 4 MΩ, standard capacitance (τ= 50 ms). Voltage traces, vertical lines and numbers are as in Fig. 3.