Activation levels, EEG, and behavioural responses.

Fifteen male alcoholic patients, who were divided into 3 different groups and treated for 3 weeks with placebo, phenobarbital or diazepam, were examined once a week in 3 different states of activation, varying from relaxation to moderate and high demand attention. Frequency-analyzed EEG recording, pulse rate, drug plasma levels, mood and performance were evaluated. The aim of this paper was to find an explanation in the EEG for responding correctly or in a non-adequate way to stimuli. Based on the activation theory of vigilant behaviour, the EEG recordings of the first examination were analyzed before, during and after the presentation of specific stimuli and related to 4 types of responses (hit, miss, false response, correct rejection) to ascertain whether prestimulus patterns were connected with different types of behavioural poststimulus responses. The EEG patterns were found to be dependent on the type of drug administered as well as on the complexity of the task performed. In all 3 treatment groups, low EEG changes before stimulus onset seemed to be the necessary condition for adequate behavioural responses. A high variability between time-points seemed to indicate a subvigilant state which led to non-adequate responses and possibly to internally induced stimuli in the vigilance test to overcome this state. In the stress phase, however, the missed responses were possibly due to selective attention to the simultaneously appearing non-relevant stimuli. The conclusion must be drawn that, at least in alcoholic patients in the acute withdrawal phase, the EEG prior to and during the stimulus presentation plays a decisive role in determining the type of emerging behavioural response: the differential high variability of the EEG is response-specific, whereas the actual power values depend on the medication given and the task performed.