P300 evoked potential patterns were evaluated for two active and two
passive attentional states in which stimuli were presented in either one or
two sensory modalities. Latency to an infrequent auditory tone was shortest
when counting the frequent stimulus, longer when counting the infrequent
stimulus, longer still under a passive condition, and longest in a non-P300
condition. P300 amplitudes identifiable in the passive attentional state
were enhanced when stimuli were from two, rather than from one, sensory
modality. Implications for understanding the mechanism of attention are
discussed. Preliminary findings in traumatic brain injury patients suggest
that passive P300 responses may be useful in assessing the extent and
severity of brain dysfunction.Abstract Teaser