Electrotonic Structure and Synaptic Variability in Cortical Neurons

Abstract

Compartmental models of reconstructed cortical neurons were used to assess the relative contributions of electrotonic filtering, synaptic parameters and recording characteristics on the distribution of synaptic responses measured at the soma from synapses located throughout the dendritic tree. In voltage clamp, cable filtering alone can generate significant variability and skewed amplitude and rise time distributions similar to those seen experimentally. Measures which are already significantly low-pass filtered, such as current clamp peak amplitude and area, are much less affected by cable filtering, and in order to match the experimentally observed distributions we must postulate another source of variability. Varying the peak synaptic conductance independent of location is sufficient to match the experimental distributions of all of these parameters, without interfering with the fit of the voltage-clamp distributions. This suggests that the synaptic variability measured experimentally is due to an interplay between cable filtering and intrinsic differences between synapses.