[A new method for measuring central activation: fourier analysis of pupillary oscillations in depressed patients]

Abstract

While the changes in pupillary size during wakefulness and drowsiness are easy to understand, the origin of pupillary oscillations is quite mysterious. Waves of spontaneous pupillary constriction and dilation accompany periods of increasing sleepiness and spontaneous arousal. Lowenstein et al. (1963) demonstrated that in the dark, the pupils of young normal alert subjects show waves of dilatation and contraction lasting from about 4 to 40 s and measuring up to 0.5 mm. Furthermore, superimposed fast and very extensive oscillations were observed. The first described oscillations seemed to reflect central nervous activation. Therefore we analysed pupillary oscillations during the recording period of static pupillometry (described by the authors in 1992) which lasted for 25.6 s. Before calculating the Fourier analysis, blinks have to be identified and eliminated by means of a new technique which is called "smoothing". Using the Fourier analysis, the spectrum was divided into 5 frequency bands (0.0-0.2; 0.21-0.4; 0.41-0.60; 0.61-0.8; 0.81-1 Hz). We were also interested in the total spectrum. In order to demonstrate utilisation of the new technique, 146 male and female depressed patients (ICD-Diagnosis 296.1, 296.3, 296.1, 296.3 + 300, respectively, 300.4, 301.1, 296.1, 296.3 + 290, respectively), aged between 18 and 45 years, were investigated by means of pupillometry, followed by analysis of pupillary oscillations. The whole group of depressive patients who received antidepressive medication was compared with 64 healthy subjects of similar age to demonstrate differences in the frequency bands.(ABSTRACT TRUNCATED AT 250 WORDS)