Figure 7. Influence of morphology and passive parameters on firing rates in young and aged Traub model neurons.

a) Voltage traces recorded empirically in an aged neuron (black) in response to +230 pA and +330 pA somatic current injections, compared with the corresponding voltage responses of a model neuron tuned to fit these data (red, called ‘Baseline parameters’). Model neuron has the same morphology as the one shown in Fig. 6a₅ and labeled ‘5’ in Fig. 2b. b) f–I curves of the mean firing rates of young and aged model neurons with the Baseline parameters except scaled R_m (in red), versus the mean firing rates measured empirically (in black). Young models and data are shown as open circles, and aged models/data as closed circles. c) After adjusting passive parameters to restore firing in young neurons, R_m was higher in aged versus young models but C_m did not differ. d) Analogous f–I curves as in (b), for young and aged model neurons with the Baseline parameters except R_m and C_m customized as in (c). *: p < 0.05.