Intensity Ratio, Coherence and Phase of EEG during Sensory Focused Attention

摘要

Intensity ratios, coherence and phase relationships of 10 c/sec EEG among six scalp locations were obtained from 20 subjects during focused attention on visual and auditory decision tasks. The analysis was based on 2 sec epochs immediately preceding subjects' decisions, in which gradually changing stimulus parameters led to a decision, as opposed to the usual sudden onset stimulus presentation. It was assumed that the subjects' attention was maximally focused on the information content of the stimulus during this period. The distributions of intensity ratio, coherence and phase were ensemble-averaged across trials to reduce their variances. The results suggest that during focused attention, the intensity ratios and phase angles do not differentiate sensory mode, but that right fronto-occipital coherence may be less during visual attention than auditory attention. Furthermore, the left hemisphere shows a negative phase angle during the auditory task but not the visual, although the distribution of phase angles is highly variable across subjects. The phase angles obtained in this study are contrasted with those obtained in a previous study in which passive, as opposed to focused, attention was maintained. (Author)