Evidence Consistent with Accelerated Inhibitory Build-up Following Stronger Subliminal Motor Activation: An EEG Trajectory-Fitting Analysis.

Subliminal motor inhibition is a crucial form of unconscious cognitive control that protects the sensorimotor system from interference to some extent. A large body of evidence has shown that this inhibition is strengthened in response to strong subliminal activation. Beyond inhibitory strength, the build-up rate of inhibition is another critical dimension of cognitive control. Nevertheless, it is unclear whether the build-up rate of inhibition varies. This study investigated this by using the mathematically derived slopes of lateralized readiness potential (LRP) waveforms as build-up rates. LRP trajectory-fitting analysis showed that the peak amplitude and slope of the inhibition-related phase in the LRP were significantly higher in the valid- than the invalid-compatible condition, but the latencies of all inflection points or the time interval between them did not differ significantly between the two cue validity conditions. Time-frequency analyses and computational modeling showed correlational patterns consistent with the accelerated inhibitory build-up. Specifically, the midfrontal theta oscillation, a neural marker linked to cognitive effort, significantly correlated with the LRP slope of the inhibition-related phase in the valid-compatible condition, even after statistically controlling for amplitudes of prime activation and inhibition. Computational modeling showed that the result for the drift rate parameter was consistent with the result for response time (RT). Taken together, these results were consistent with the hypothesis that increased subliminal activation is followed by strong inhibition at a high build-up rate, thereby preventing the strong interference signals from escaping or being delayed inhibition. This reflects the high degree of adaptability and flexibility of the unconscious cognitive system when interacting with the environment.