The biomechanical state of the effector affects motor control and provides measures of single trial inhibition in a stop signal task

Abstract

AbstractThe Stop Signal Task (SST) has been the benchmark for studying the behavioral and physiological basis of movement generation and inhibition. In our study, we extended the scope beyond physiological findings related to muscle activity, focusing our analysis on the initial biomechanical state of the effector. By incorporating a force sensitive resistor (FSR), we continuously monitored the force applied by the effector (here the index finger) during a button release version of the SST. This modified task design allowed us to examine both the baseline force before the relevant Go signal was presented and during the covert state of movement preparation. Notably, variations in force over time in response to the Go signal revealed differences across trials where movement was either generated or successfully inhibited, depending on the amount of force during the baseline period. Specifically, higher baseline force was associated with a delayed movement generation, which, simultaneously slowed down the force release, facilitating successful inhibition when requested. Our results highlight the influence of biomechanical variables in movement control, which should be accounted by the models developed for investigating the physiology of this ability.Significant statementMovement involves changing the position of anatomical effectors, such as a finger, and the initial condition of an effector, including its resting biomechanical state, can impact both movement generation and inhibition. The Stop-Signal task, widely employed to study motor control variables, has focused on neural conditions preceding movement initiation but has often overlooked biomechanical factors. We studied these variables by measuring the force applied to a mouse button before movement onset during a button release task. The results indicate that higher initial force on the button delays movement generation and slows force release, thereby aiding successful movement inhibition. This research bridges behavioral models of action stopping with the biomechanics of movement, emphasizing the importance of the effector’s initial state.