How Evoked Slow Wave Can Influence the Shape of PST Histogram of Neurons' Spike Activity

Abstract

The neurons' electrical activity recorded by a microelectrode often contains a slow wave on which the spikes are superimposed. To evaluate the PST histogram of spikes in response to stimuli such as acoustic clicks [to be called p(t), o < t < T], one passes the signal through a threshold device. Choosing a high threshold level ensures that only spikes are counted but will cause some occasional omission. Under certain conditions the omission of spikes influences the shape of PST histogram. By using a mathematical formulation, conditions under which the PST histogram resembles the average of evoked slow wave [to be called r(t), o < t < T] are discussed. When the spike activity is not correlated with stimulus and slow wave is very small compared with the height of the spikes, the threshold level p(t) = A + Br(t), where A is proportional to the level of spontaneous activity of neuron and B is inversely proportional to standard deviation of slow wave. Thus, with some distortion, p(t) resembles r(t). Results are illustrated by simulation on a digital computer. [Supported by Aria-Mehr University.]