Sequential processing in the equiprobable auditory Go/NoGo task: a temporal PCA study.

The unwarned auditory equiprobable Go/NoGo task provides a convenient means to assess differential processing, although our interpretations remain limited by the lack of research regarding the range of elicited components and their functional significance. We examined sequential processing in this paradigm, presenting 24 participants with a total of 300 trials in two blocks. EEG was recorded from 19 channels, and the Go and NoGo event-related potentials were decomposed using temporal Principal Components Analysis. Of the 218 unrestricted Varimax-rotated factors, seven were identifiable as components based on their latency, polarity, and topography: early N1, Processing Negativity (PN), and P2 components were followed by N2, P3, the classic Slow Wave (SW), and a diffuse Late Positivity (LP). N1 was enhanced to Go, as was the defining temporal topography of PN. NoGo produced increased centroparietal P2, frontocentral N2, and P3a, in comparison to Go, which produced a more parietal N2 and P3b, and an enhanced SW. The LP was larger in NoGo. These results suggest that N1 marks the beginning of Go and NoGo differentiation. Complete Go/NoGo categorisation is marked by N2; this is followed by different processing chains leading to the NoGo non-response (marked by P3a) and Go response (marked by P3b and SW). The larger LP in NoGo marks the cortical inactivation following the earlier cessation of processing in this condition.