Spatial patterns in EEG activity during monotonous sound perception test

We present a study of quantitative characteristics of a test subject attention associated with analysis of EEG-records in test subjects. Twelve overall healthy subjects 20–35 years old (5/7 male/female) with complaints about daytime sleepiness were included. Multichannel electroencephalography was conducted during the monotonous sound perception test. The processing of the EEG signals was based on the adapted method for assessing spatial patterns using the Karhunen–Loeve transformation. We used descriptive statistics to summarize our findings. All experimental time was classified into active stages with reaction to sound stimuli and passive stages, in which subjects demonstrated drowsiness without reaction to presented stimuli. An analysis of EEG activity in conjunction with assessment of the patient response enabled us to identify a characteristic scenario of adaptation to the task of maintaining attention to sound stimuli in this group. Active stages with a minimum reaction time of response to the signal and maximum duration were preceded by an increase in the spatial activity complexity on the EEG of the left hemisphere during the passive stage without responses. The passive stage of drowsiness without response to stimuli was actively involved in the process of adaptation to prolonged monotonic activity in patients with increased daytime sleepiness.