Central nervous activation in opoid dependent patients evaluated by means of Fourier analysis of pupillary oscillations

The aim of the present investigation was to determine whether Fourier analy sis of pupillary oscillations permits detection of differences in the activ ation of the central nervous system of opioid-addicted patients. We analyse d pupillary oscillations during the recording period of static pupillometry , which lasted 25.6 s. Using Fourier analysis, the spectrum was divided int o five frequency bands (0.0-0.20, 0.21-0.40, 0.41-0.60, 0.61-0.80, 0.81-1.0 Hz); the total spectrum (0-1 Hz) was also assessed. Three groups of patien ts were selected: the group addicted to heroin (consuming exclusively heroi n) consisted of 26 patients with a mean age of 25.0 +/- 6.3 years, the meth adone substitution group of 20 patients with a mean age of 30.9 +/- 8.2 yea rs, and the morphine substitution group of 20 patients with a mean age of 3 3.2 +/- 4.6 years. The 3 patient groups were compared with normal controls of similar age (25.1 +/- 4.6 years). In the frequency band of 0.0-0.20 Hz t he morphine group showed significantly lower amplitudes than the heroin gro up. Also in the frequency band of 0.41-0.60 Hz the morphine group differed significantly from the other groups concerning lower amplitudes, reflecting deactivation. In the total spectrum of 0 to 1 Hz the differences between t hese two groups were significant. Comparison with normal controls also show ed significant differences. The groups were further divided according to do se (high/low): Patients of the heroin group as well as those of the methado ne and morphine groups who had consumed higher doses showed greater activat ion of the central nervous system. In conclusion the morphine group was more deactivated than the methadone an d heroin group and patients who received higher doses of the substances sho wed greater central nervous activation. Thus, the measurement of central ne rvous activation by means of Fourier analysis of pupillary oscillations mig ht be useful in monitoring substitution therapy.