Spiking Neurons: Is coincidence-factor enough for comparing responses with fluctuating membrane voltage?

摘要

Similarity between two spike trains is generally estimated using a 'coincidence factor'. This factor relies on counting coincidences of firing-times for spikes in a given time window. However, in cases where there are significant fluctuations in membrane voltages, this uni-dimensional view is not sufficient. Results in this paper show that a two-dimensional approach taking both firing-time and the magnitude of spikes is necessary to determine similarity between spike trains. It is observed that the difference between the lower-bound limit of faithful behaviour and the reference inter-spike interval (ISI) reduces with the increase in the ISI of the input spike train. This indicates that spike trains generated by two highly-varying currents have a high coincidence factor thus indicating higher similarity - a limitation imposed due to a one-dimensional comparison approach. These results are analysed based on the responses of a Hodgkin-Huxley neuron, where the synaptic input induces fluctuations in the output membrane voltage. The requirement for a two-dimensional analysis is further supported by a clustering algorithm which differentiates between two visually-distinct responses as opposed to coincidence-factor.