Figure 11.
Impact of dendritic membrane properties on optimal AIS length. A, Diagram of a neuron with four dendrites having variable dendritic membrane properties and a variable-length AIS attached to a myelinated axon (AIS Model A). B, Voltage responses in the AIS following somatic current injections under baseline conditions (far left) and after manipulations of dendritic RM and/or CM, as indicated. Responses from three model neurons having AIS lengths of 75 (blue), 85 (green), and 95 (red) µm are superimposed. C, Plots of normalized rheobase current vs AIS length for the four dendrite model having modified dendritic RM (top left; inset shows close-up of indicated area), dendritic CM (top right), parallel changes in both dendritic RM and CM (bottom left), or reciprocal changes in dendritic RM and CM (bottom right). Dendritic CM and/or RM were multiplied by the indicated modification factors. In experiments testing reciprocal changes in dendritic properties (bottom right), the CM/RM ratios represent reciprocal changes to CM and RM around the baseline (CM/RM ratio = 1) values (e.g., a ratio of 0.25 indicates that dendritic CM was multiplied by 0.5 and dendritic RM was multiplied by 2.0). Increasing dendritic CM favored a longer AIS, regardless of whether there were also co-occurring changes in dendritic conductance (i.e., changes in dendritic RM). Shaded bars indicate the AIS lengths for which traces are shown in B.