A CNV-like negative shift in deep coma

Abstract

In order to elucidate the unsolved problem of the genesis and “contingency” of the CNV, which is largely related to attention, expectancy and other attentive activities, two patients in deep coma were stimulated by means of repeated sets of paired stimuli (click, S 1, and flash, S 2, 900 msec later). The recorded responses were analysed according to the method generally applied for the detection of CNV in normal subjects. The standard EEG, eye movements and steady potential shift from the vertex, using the left mastoid as reference, were recorded. Relevant negative shifts between S 1 and S 2 were recorded from the vertex only after a great number of paired stimuli (120 and 150, respectively). Control experiments proved that artifacts and extracerebral potentials were not involved in eliciting this phenomenon. The slow negative potentials recorded did not differ morphologically from CNV in normal subjects but only in the number of paired stimuli required for their appearance.