Physiological variability of peak latency in evoked potentials: use of a property of asynchronous averaging

A method for estimating the physiological variability of peak latency in an evoked potential, of whom the peak latency and amplitude varied, by using the property of asynchronous averaging was proposed. A point estimate of the physiological variability was obtained by minimizing the mean square error between a standard waveform and the asynchronously averaged waveform. An interval estimate was obtained by using the relationship between the signal-to-noise ratio and the standard deviation of the point estimate for the variability of peak latency. The proposed method was evaluated by using simulation data, and was successfully applied to actual P300 data of six normal subjects. The method gave accurate estimates for the physiological variability of peak latency of P300, and would also be effectively applicable to any other evoked potential records for estimating the physiological variability.