Temporal Preparation and Executive Functions in the Context of a Variable Foreperiod Stop-Signal Paradigm in Macaque...

The interaction between temporal preparation and response inhibition is poorly understood in primates. Across two experiments, we investigated this relationship in four rhesus monkeys (Macaca mulatta) using a variable foreperiod (FP) stop-signal task, respectively focusing on effects of FP and its repetition/alteration across trials on response inhibition. We estimated ex-Gaussian distribution of reaction time in go trials (Go-RT) and stop-signal reaction time (SSRT) along with a probability of trigger failure (PTF). In the first experiment, increasing temporal preparation reduced the mean and variability of both the Gaussian and exponential components of Go-RT distribution, indicating generally faster and more consistent responding. In contrast, temporal preparation produced divergent effects on SSRT distribution: it numerically increased the Gaussian mean but decreased the exponential tail and overall variability. At the same time, PTF increased from short to long FP, suggesting that temporal preparation hinders the trigger of inhibition while enhancing its efficacy once triggered. In the second experiment, we found that FP effects on Go-RT distribution were largely independent of FP sequence. By contrast, response inhibition in the Gaussian component and entire distribution was modulated by FP switching: alternation between FPs prolonged inhibition latency. Also, FP switching reduced trigger failure, indicating a sequential adjustment that improved cue detection and reliability of stopping. Together, these findings demonstrate that temporal preparation shapes response execution primarily independent of state of preparation in the preceding trial, whereas its influence on response inhibition reflects short-term influences from the preceding trial.