Quantal behaviour of synaptic transmission can be statistically examined using the Fourier line spectrum of the histogram of synaptic potentials.

A statistical approach to reveal the quantal behaviour of postsynaptic potentials (PSPs) is described. This includes: (1) obtaining the Fourier line spectrum (decomposition into harmonics) of the PSP histogram; and (2) testing the null hypothesis, 'the spectrum is that of white noise', using an ANOVA. The harmonic that rejects the hypothesis will indicate the regular peaks in the histogram, i.e., the quantal size of PSPs. The method was tested using published results of three experimental studies in central synapses and yielded the quantal sizes close to those derived from other methods. However, using three examples of published simulation studies (where the quantal model of synaptic transmission was known a priori), it was shown that the approach can estimate quantal sizes of PSPs more reliably than other methods.