Comparison of QEEG and response accuracy in good vs poorer performers during a vigilance task.

Subjects performed an auditory continuous performance test requiring them to detect targets in a series of letters presented at a rate of 2/s. 2-min samples of EEG were obtained from eight bipolar sites during a resting condition and during early and late (7-10 min) test performance. EEG power spectra from 27 subjects whose performance accuracy decreased between these latter periods (LoVig group) were compared with those from 27 subjects who maintained a constant level of performance (HiVig group). In both groups EEG power changed significantly between resting and test conditions for all frequency bands: beta power increased, especially in fronto-temporal and temporal left-hemisphere sites; alpha and posterior theta decreased; anterior theta and delta increased. Significant changes also were found between early and late test performance: anterior theta and delta power decreased in both groups; temporal beta power decreased in the LoVig group only, and is thus considered the best indicator of performance changes. Other differences found between groups were across conditions. The HiVig group had more anterior beta and less posterior alpha and theta than the LoVig group. EEG results are discussed in relation to an explanation of vigilance errors based on signal detection theory.