Event-related brain potentials and attention during simultaneous performance of two tasks.

Subjects were required to perform simultaneously a compensatory manual tracking task and an auditory discrimination task. Four behavioral measures, root-mean-square-tracking error, reaction-time, Sensitivity and Response Bias, and two physiological measures, peak amplitudes and peak latencies of the "negative difference" even-related brain potential, were used to assess the distribution of attention during task performance. Approximately 200 msec. after stimulus onset (peak latency M = 206.6 msec.), the negative difference potential's peak amplitude was more positive for tones irrelevant to the discrimination task and less positive for tones relevant to the discrimination task. This pattern of change suggests that irrelevant tones receive less attention during simultaneous performance of the tasks than during performance of the discrimination task alone. Moreover, the data suggest that the redistribution of attention while simultaneously performing the tasks directly affects processing in the sensory areas of the auditory cortex.