A NEW TECHNIQUE FOR MEASUREMENT OF CENTRA L NERVOUS ACTIVATION - FOURIER-ANALYSIS OF PUPILLARY OSCILLATIONS IN DEPRESSED-PATIENTS

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 a ccompany periods of increasing sleepiness and spontaneous arousal. Low enstein et al. (1963) demonstrated that in the dark, the pupils of you ng normal alert subjects show waves of dilatation and contraction last ing from about 4 to 40 s and measuring up to 0.5 mm. Furthermore. supe rimposed fast and very extensive oscillations were observed The first described oscillations seemed to reflect central nervous activation. T herefore we analysed pupillary oscillations during the recording perio d of static pupillometry (described by the authors in 1992) which last ed for 25.6 s. Before calculating the Fourier analysis. blinks have to be identified and eliminated by means of a new technique which is cal led ,,smoothing''. Using the Fourier analysis, the spectrum was divide d 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 dem onstrate utilisation of the new technique. 146 male and female depress ed patients (ICD-Diagnosis 296.1. 296.3, 296.1, 296.3 + 300, respectiv ely, 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 pati ents who received antidepressive medication was compared with 64 healt hy subjects of similar age to demonstrate differences in the frequency bands. Concerning the amplitudes in the frequency bands of 0.0-0.2 Hz , 0.2-0.4 Hz as well as 0.0-1.0 Hz (total spectrum), significant diffe rences between depressed patients and normals were observed. reflectin g reduced central activation in depressed patients. Furthermore, the d ifferent depressive groups showed deactivation as compared with neurot ics.