Cumulative sum technique and its application to the analysis of peristimulus time histograms.

The cumulative sum procedure introduced by Hurst (1950) involves subtraction of a control reference level from a series of datum points and adding the differences consecutively. The resultant curve shows trends indicating changed levels of points. The technique has been applied to peristimulus time histograms in order to reveal small changes in the probability of spike occurrences normally obscured by random fluctuations. The combined process of cumulative sum and PSTH cuts the overall number of trials needed in real time and reduces the uncertainty of decision making during the experiment.