This is the readme for the model associated with the paper: Fernandez FR, Mehaffey WH, Turner RW (2005) Dendritic na+ current inactivation can increase cell excitability by delaying a somatic depolarizing afterpotential. J Neurophysiol 94:3836-48 Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Dr. N.W., Calgary, Alberta T2N 4N1, Canada. rwturner@ucalgary.ca. Many central neurons support active dendritic spike backpropagation mediated by voltage-gated currents. Active spikes in dendrites have been shown capable of providing feedback to the soma to influence somatic excitability and firing dynamics through a depolarizing afterpotential (DAP). In pyramidal cells of the electrosensory lobe of weakly electric fish, Na(+) spikes in dendrites undergo a frequency-dependent broadening that enhances the DAP to increase somatic firing frequency. We use a combination of dynamical analysis and electrophysiological recordings to demonstrate that spike broadening in dendrites is primarily caused by a cumulative inactivation of dendritic Na(+) current. We further show that a reduction in dendritic Na(+) current increases excitability by decreasing the interspike interval and promoting burst firing. This process arises when inactivation of dendritic Na(+) current shifts the latency of the dendritic spike to delay the arrival of the DAP sufficiently to increase its impact on somatic membrane potential despite a reduction in dendritic excitability. Furthermore, the relationship between dendritic Na(+) current density and somatic excitability is nonmonotonic, as intermediate levels of dendritic Na(+) current exert the greatest excitatory influence. These results reveal that temporal shifts in dendritic spike firing provide a novel means for backpropagating spikes to influence the final output of a cell. These files were supplied by Dr Fernandez ffernand@ucalgary.ca If you have the sigmal processing toolbox you can run the matlab program ELLburstpyramidal.m, otherwise run the matlab program ELLburstpyramidal_noSigProcToolbox.m