An Adaptive Method for Testing for Change in Digitized Cardiotachometer Data

An adaptive method for detecting change in digitized cardiotachometer recordings has been developed which takes into account the nonstationary statistical structure of the data. The digitized data are smoothed to reduce the variance at high frequencies caused by discontinuities inherent in cardiotachometer output. Based on a first-order autoregression, which has been shown to be appropriate for heart rate data, the adaptive procedure uses estimates of the parameters which are most influenced by the recent observations. Decreasing weight is given to past prestimulus data, and the estimates are updated with each stimulus. A test for change is then applied to the poststimulus regions at each time point, yielding a t statistic. The t 2 's can then be averaged to give a test for change over an interval.