EEG coherence pattern during simultaneous and successive processing tasks.

In order to investigate psychophysiological basis of two different types of information processing (simultaneous and successive), we investigated EEG coherence patterns during five tasks of the Das-Naglieri Cognitive Assessment System. The investigation was based on the perspective of the similarities among the tasks of the same processing type and discrepancies between the different processing types. EEG coherence of eighteen volunteers during two simultaneous and three successive tasks varying in task content (verbal-nonverbal) and modality (auditory-visual) was computed. First, we compared the coherence patterns between the tasks of the same processing type, then compared between the tasks of different processing types. Result revealed a specific theta coherence pattern associated with processing type regardless of task contents and modality. Theta coherence during the simultaneous processing showed increased short-range inter-hemispheric connections over central and parietal regions as compared to the successive tasks. Upper beta coherence indicated task-dependent effect regardless of processing types. In addition, our data indicated no hemispheric differences for both processing types. It suggested that confounding of verbal-nonverbal and processing type (simultaneous-successive) dimension could be avoided. Our result presented psychophysiological evidence for the existence of two types of information processing, which has been supported by psychological studies with factor analysis.