Department of Electronics University of York YORK YO10 5DD

Synaptic integration in single neurones involves spatial temporal interactions between large numbers of inputs to a dendritic tree. We use a computer model to characterise the relationship between the membrane potential fluctuations in different locations of the dendritic arbor during different patterns of synaptic input to a simulated compartmental model of a motoneurone. We look at a single input applied in isolation, and as part of large scale synaptic input, provided by 996 independent synaptic inputs, to a model consisting of a soma plus 12 tapered dendrites of varying electrotonic length. Correlation analysis of membrane potential fluctuations reveals a complex interaction, suggesting the presence of feedback. Traces of the axial membrane current indicate that a feedback mechanism occurs in the dendrite following individual synaptic inputs. This feedback mechanism takes the form of a reversal of the axial membrane current flowing in the distal direction. This feedback, which occurs on the time scale of 1-2 ms, tends to smear out the effects of individual inputs and is likely to contribute to the correlation structure seen between membrane potential fluctuations in the dendritic tree, and has implications for our understanding of synaptic integration.

In: British Neurosci. Assoc. Abstr., vol17, p151, 2003.