Quantal analysis based on spectral methods.

A method for calculating quantal size based on spectral analysis of postsynaptic potential (PSP) amplitude distributions was developed and tested by Monte-Carlo techniques. It was combined with a test to reveal the bias of the estimate of quantal size and to determine whether the peaks in amplitude distributions reflect quantal release or a sampling artifact. Spectral density was computed using fast Fourier transformation after subtraction of a fitted polynomial from the probability density function.

Modeling of the quantal release at interneuronal synapses: analysis of permissible values of model moments.

A theoretical study of effects of the different factors on fluctuation of post-synaptic potential (PSP) amplitudes was undertaken, using computation of regions of permissible values (RPV) of the ratio between the variance and the mean number of the quanta released (R1) and the ratio between the third moment and the variance (R2). The RPVs of these indexes for the binomial model were compared with regions determined for a number of models incorporating several factors. It has been shown that the involvement of temporal non-uniformity of transmitter release probability, decremental spreading of potentials along dendrites, and failure of spike propagation give the values of skewness index R2 less, compared to the binomial model.