Fig. 4.

Influence of local changes in the membrane conductance, g_pas, on attenograms from the model in Fig. 2. (A, B) Effects of changing the passive conductance of one segment of the dendritic tree (dashed line). Attenograms in A were generated with a current clamp at the IS; those in B with the clamp at the tip of a distal dendrite (as shown in Fig. 2B). The passive parameters for the equivalent cable were the same as in Fig. 2 for all dendrites except for the segment indicated by the dashed line: g_pas (in Ω⁻¹ cm⁻²)=10⁻³ for the left panels, 10⁻⁴ for the middle panels, and 10⁻⁵ for the right panels. Note the difference in scales in A and B. The segment in which electrotonic length was affected by the change in membrane conductance is represented by a thick line. Note that there is little difference between the middle and right panels because as g_pas becomes smaller, the axial resistance (R_a=50 Ω cm) becomes the dominant factor in determining the electrotonic length of the dendrite.