P300 AND ALLOCATION OF ATTENTION IN DUAL-TASKS

P300 in dual-tasks has been reported to be distributed reciprocally ac ross the tasks, i.e. larger P300 associated with one task implies smal ler P300 associated with the other (Wickens et al., 1983; Sirevaag et al., 1989). In these studies, however, the dual-task stimuli were eith er presented simultaneously, precluding a direct, within-trial assessm ent of relative magnitudes of P300, or they were separated by interval s of 1 s or more, thereby minimizing overlap of the ERP epochs, but at the cost of reduced competition for shared processing resources. The present experiment used an inter-stimulus interval of 400 ms between t he auditory (tones) and visual (colored LEDs) stimuli that defined the dual-task and found that when deviant tones elicited a prominent audi tory P300, they were followed by a greatly reduced P300 for the devian t LED. The findings were interpreted from viewpoints that considered t he effects of neural inhibition versus neural recovery cycles on the a mplitude of P300.