Auditory equiprobable NoGo P3: A single-trial latency-adjusted ERP analysis.

The NoGo P3 event-related potential (ERP) component is often related to response inhibition, although its function in equiprobable Go/NoGo tasks is debated. Previous findings concerning the auditory equiprobable NoGo P3 (or P3a) could be distorted by averaging latency-variable ERP components. This study aimed to control NoGo P3 latency jitter to investigate the component's relationship with inhibitory demands and its neuronal sources across trials. P3 latency jitter was controlled using a novel procedure to enable single-trial P3 quantification across 126 healthy young adults (Mage = 20.3, SD = 2.8 years) using principal components analysis. NoGo inhibitory demands and performance were measured using the Lateralised Readiness Potential and error rates, respectively. The stimulus-locked P3 (SL-P3) was also analysed to assess the 'blurring effect' (i.e., smearing) associated with averaging latency-variable ERP trial data. A Spearman's rank correlation across 4700 NoGo trials demonstrated that the relationship between latency-adjusted P3 (LA-P3) and inhibitory demands was inconsequential. The cortical sources associated with LA-P3, using eLORETA, were in the premotor and prefrontal cortices, cingulate, and precuneus. SL-P3 was smaller than LA-P3, and that difference was positively related to P3 latency jitter; its source solution was also limited to lower activation in the prefrontal cortex. SL-P3 was not related to inhibitory demands or performance. This study indicates that NoGo P3 should not index response inhibition in auditory equiprobable tasks. Instead, the findings support a neuroinhibition account relating NoGo P3 to attention. Blurring effects were also shown to impact a standard ERP measure and its source solution, encouraging ERP latency-adjustment in future research.