PT  - JOURNAL ARTICLE
AU  - An T. Nguyen
AU  - Matthew A. Albrecht
AU  - Ottmar V. Lipp
AU  - Welber Marinovic
TI  - Motor Output Matters: Evidence of a Continuous Relationship Between Stop/No-go P300 Amplitude and Response Force on Failed Inhibitions at the Trial-Level
AID  - 10.1101/706978
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 706978
4099  - http://biorxiv.org/content/early/2019/07/29/706978.short
4100  - http://biorxiv.org/content/early/2019/07/29/706978.full
AB  - Motor actions can be suppressed with varying degrees of success, but this variability is not captured in many experiments where responses are represented in binary (response vs. no-response). Although the Stop/No-go P300 (an enhanced frontocentral positivity in the event-related potential (ERP) peaking around 300 ms after a Stop/No-go stimulus, compared to Go trials) has been implicated as a measure of inhibitory-control, it is unclear how the range of motor outputs relates to the P300. We examined the nature of this association in two experiments using an Anticipatory Timing and a Go/No-go Task. Force, response onset time, and the P300 were measured.In both experiments, our results showed that trial-by-trial P300 amplitude on Failed Inhibitions were continuously related to Force, where higher response forces (reflecting a greater degree of error) were associated with smaller P300 amplitudes. Compared to Successful Inhibitions, P300 amplitude was reduced and ERP onset latencies were delayed on Failed Inhibitions. Although the binary categorisation of inhibition-success (Successful vs. Failed) accounted for more variance in the data compared to force, it misses a reliable linear relationship that can be captured by continuous measures of motor output. Overall, the results provide strong evidence that the engagement of inhibitory-control varies on a continuum from trial-to-trial and that this engagement is reflected by the P300. We present an activation-to-threshold model of inhibitory-control to explain our results, which offers a new conceptual framework for describing the implementation of inhibitory-control in highly prepared motor responses. Our results also highlight the importance of studying the spectrum of motor outputs and the need for future models of inhibitory-control to account for motor output.