Parsing the late positive complex: mental chronometry and the ERP components that inhabit the neighborhood of the P300.

Falkenstein, Hohnsbein, and Hoorman (1994) suggested that common measures of P300 latency confound a "P-SR" component whose latency corresponds to stimulus evaluation time and a "P-CR" component whose latency varies with response-selection time, thus casting doubt on work in mental chronometry that relies on P300 latency. We report here a replication and extension of Falkenstein et al. (1994) using a high-density 129-electrode montage with 11 subjects. Spatiotemporal PCA was used to extract the components of the ERP. A centroid measure is also introduced for detecting waveform-timing changes beyond just peak latency. In terms of componentry, we argue that the P-SR and the P-CR, correspond to the P3a/Novelty P3 and the P300, respectively. Conceptually, we dispute the proposed distinction between stimulus evaluation and response selection. We suggest a four-stage ERP model of information processing and place the P3a and the P300 in this framework.