Slow wave and P300 in signal detection

Abstract

CNV, P300 and slow wave amplitude correlates of auditory detection accuracy were studied for both hits and correct rejections. Baseline-to-peak measures gave no indication of the downturn of P300 at very high detection accuracies reported by Hillyard et al. (1971). Principal Components-Varimax Analyses (PCVA) of the event-related potentials (ERPs) were performed. The PCVA basis wave forms for P300 and slow wave showed that baseline-to-peak measures of P300 represent a composite of the two. The weighting coefficients for P300 and slow wave showed an opposite pattern in relationship to accuracy: P300 weighting coefficients increased monotonically with increased accuracy, whereas slow wave weighting coefficients decreased monotonically with increased accuracy. For both P300 and slow wave, findings were similar for both hits and correct rejections. These and earlier findings (Roth et al., 1978; Ruchkin et al. 1980) suggest that overlap between P300 and slow wave should be examined in future P300 experiments. No differences were found in relation to experimental conditions for the CNV in the baseline-to-peak measures or in the PCVA measures. The PCVA showed that there was significant CNV activity in the post-stimulus epoch and therefore the CNV represents another source of overlap with P300 and slow wave when peak-to-baseline measures are used. P300 and slow wave PCVA components have little activity in the pre-stimulus epoch indicating that they are determined by post-stimulus events. The increase of slow wave amplitude with decreasing accuracy is interpreted as reflecting the need for further processing when intensity is so low as to make a decision difficult. This ‘further processing’ interpretation is consistent with other studies in which slow wave has been shown to vary with task demands