The independent components of auditory P300 and CNV evoked potentials derived from single-trial recordings

Abstract

The back-projected independent components (BICs) of single-trial, auditory

P300 and contingent negative variation (CNV) evoked potentials (EPs) were

derived using independent component analysis (ICA) and cluster analysis.

The method was tested in simulation including a study of the electric dipole

equivalents of the signal sources. P300 data were obtained from healthy and

Alzheimer’s disease (AD) subjects. The BICs were of approximately 100 ms

duration and approximated positive- and negative-going half-sinusoids. Some

positively and negatively peaking BICs constituting the P300 coincided with

known peaks in the averaged P300. However, there were trial-to-trial

differences in their occurrences, particularly where a positive or a negative

BIC could occur with the same latency in different trials, a fact which would be

obscured by averaging them. These variations resulted in marked differences in

the shapes of the reconstructed, artefact-free, single-trial P300s. The latencies

of the BIC associated with the P3b peak differed between healthy and AD

subjects (p < 0.01). More reliable evidence than that obtainable from single- trial or averaged P300s is likely to be found by studying the properties of the

BICs over a number of trials. For the CNV, BICs corresponding to both the

orienting and the expectancy components were found.