Distinguishing theoretical synaptic potentials computed for different soma-dendritic distributions of synaptic input.

Abstract

Computations with a mathematical neuron model predict numerous consequences of different synaptic input distributions. The shapes of computed synaptic potentials are characterized by quantitative shape indices, whose dependence upon synaptic input location, time course, and upon dendritic electrotonic length is demonstrated and discussed in terms of electrotonic spread over the soma-dendritic membrane surface. A computational dissection of several electric current transients and membrane potential transients illustrates how a dendritically located synatic conductance transient produces a synaptic potential at the soma. Departures from linearity for various intensities of synaptic excitation, and for combinations of synaptic excitation and inhibition, are illustrated and explained in terms of the effective driving potential at each site where a synaptic conductance transient occurs; the effects of applied hyperpolarizing current upon computed synaptic potentials are also explained in these terms. The relative detectability at the soma of transient conductance at different dendritic locations is illustrated quantitatively.