Using recursive parameter estimation for sleep disorder discrimination

The human pupillary light reflex has long been studied as a typical biological nonlinear system. We have used a sinusoidal non-harmonic signal as the input light stimulus and pupil diameter as the output of the system. A recursive least square method is then used to estimate the measured pupil diameter in terms of the input light. With a good estimate, the underlying dynamical behavior of the system would be captured by the estimated parameters. Thus we modeled the estimated parameters as ARIMA processes. Then the residual noise associated with the ARIMA models was examined and revealed that people with narcolepsy had considerably lower sum-square-error than people without this sleep disorder (controls). This method turns out to be a relatively simple and fast test procedure for narcolepsy discrimination