[Effects of divided attention to visual and auditory stimuli on event-related potentials]

Effects of cross-modal divided attention on event-related potentials (ERPs) were examined. Tone pips through either left or right headphones, and colored words, either red or blue on a CRT display were presented in random order with equal probabilities (.25). Each class of stimuli included rare target tones or words. Eight subjects were instructed to attend 1, 2, 3 or all of four classes of stimuli in various combinations and to press a button quickly when targets occurred in the attending classes. ERPs to non-target stimuli in each class were recorded. Attention-related negative components of ERPs were largest when attention was focused upon only 1 class of stimuli, and their amplitudes decreased when attention was divided. A greater attenuation of ERPs was caused by the intra- rather than inter-modally divided attentions. The results suggest that the attention-related negative components may reflect the limitation of capacity or interference among sub-mechanisms in each of visual and auditory modalities.