Sedation threshold and Archimedes' spiral after-effect in early psychosis

Abstract

IT IS a commonplace though clinically neglected fact that individuals differ in their tolerance of sedative drugs. The first formal attempt to quantify this variation was made by SHAGASP using changes in the barbiturate-induced fast activity in the frontal leads of the electroencephalogram to define an end-point, the ‘sedation threshold’. Using a behavioural method for the determination of the threshold, the authors have previously2J investigated its relation, in neurotic and normal subjects, to personality variables and to a number of psychological and physiological measures. Of these, a simple and therefore clinically useful test, the after-image experienced following fixation of an Archimedes’ spiral, was found to correlate significantly with the sedation threshold. Dysthymics(anxiety states) had high sedation thresholds and reported long after-images, hysterics had low values on both measures and the figures for normal subjects were scattered between the two neurotic groups. It seemed of interest to investigate these measures in patients with psychotic illness, particularly since available evidence indicated that the correlation found in neurotics would not hold. CLARIDCE~ found that the mean after-effect in schizophrenics was a little longer than normal, whereas it is known that early psychosis is characterized by low tolerance to depressant drugs.175 Since this study was completed KRISHNAMOORTI and SHAGAS@ in addition to confirming the authors’ findings in neurotic patients, found a negative, though statistically non-significant, relation between threshold and S.A.E. in a group of acute and chronic schizophrenics. In all studies, the range of values was large, and it is likely, as in the neuroses, that the type of illness and premorbid personality account for some of the variation. Therefore, in addition to the objective measures, clinical features of the illness were rated for each individual in the hope of demonstrating such relationships, though no confident predictions were possible on the basis of available knowledge. In order to determine whether recovery from psychosis is reflected in changes of the objective tests, the Archimedes’ spiral and sedation threshold were redetermined in those cases showing good clinical remission.