Figure 4.

A model neuron used for simulating changes in τ_in and R_in. (A) Three cell lengths (150, 300, and 1200 μm) are illustrated. For each cell length R_m started at 5 kΩcm² and increased 50% of the last value for each run, up to 57 kΩcm². This range is given as the x-axis in B and C. (B) A steady-state voltage induced by a long-lasting current injection into the soma has lower amplitude at the tip of the dendrite than in the soma. The amplitude at the tip of one dendrite is given as the percent of the somatic amplitude. (C) The increases in τ_in and R_in were compared with a chosen 50% increase in R_m. τ_in increased almost proportional to R_m in the cells that were 150 and 300 μm (open circles). When the cells became very long (more than half the diameter of the cord), τ_in increased considerably less than R_m, reflecting the limitations of our approach to measure the slowest time constant (see Discussion). R_in increased generally less than R_m, marked by filled circles, that gives more deviation from unity than τ_in.