Psychophysiological diagnostics in alcohol dependency: Fourier analysis of pupillary oscillations and the receptor test for determination of cholinergic deficiency

Abstract

Mnestic disturbances in alcoholics may be related to cholinergic deficiency as well as to central nervous system inactivation. After instillation of tropicamide, cholinergic receptors are blocked and pupillary dilatation occurs. It is assumed that the more severe the cognitive deterioration, the wider the pupillary dilatation. Pupillary oscillations reflect central activation. Changes of pupillary diameter after topical instillation of tropicamide and pupillary oscillations were measured in 44 alcohol-dependent patients aged 40-55 years, diagnosed according to the DSM-III-R as severe alcoholics (> 7 symptoms), having been abstinent for at least 3 weeks (objectively tested with carbohydrate-deficient transferrin), compared with 18 healthy controls. The pupillary diameter of the left eye was measured eight times within 103 min, as were pupillary oscillations. Using Fourier analysis, the amplitudes of oscillations were measured in five frequency bands and the sum of the frequency bands was calculated. In addition, central activation was measured during a calculation test at 3 and 103 min. The pupillary dilatation of 22% in alcoholics compared to 14% of normal controls after tropicamide raises the question of a cholinergic deficit in alcohol dependence. With regard to basic activation, measured by Fourier analysis of pupillary oscillations, alcoholics demonstrated significantly lower power (sum of the frequency bands) than controls at baseline and at 3, 20, and 40 min (P < 0.01) as well as at 60, 80, 100, and 103 min (P < 0.05). After a cognitive task, a difference between alcoholics and healthy controls was found at 3 min. Alcoholics showed lower basic activation and decreased cognitive activation. By means of cross-validation, a differentiation between alcohol-dependent patients (n = 44 and n = 42 respectively) and normal controls (n = 18) was possible.