Action monitoring fails when motor execution is too fast: no time for correction

A recent information processing model of two-choice RT situations (Servant et al., 2015), suggests that conditions which reduce the duration of peripheral motor processes, should also reduce the efficiency of the action monitoring system, because letting no time enough for correction of partial errors (i.e. subthreshold transient muscle activity of the agonists of the incorrect response preceding the correct response). A physiological situation, namely sustained physical exercise, has repeatedly been reported to reduce the duration of response execution. Therefore, in order to test the prediction of the model, we compared action monitoring efficiency between a sustained exercise (59.42% of MAP) and a control (15 W) condition in the same subjects while they were performing a Simon task. Electromyographic (EMG) recordings of muscles implicated in the response allowed to measure premotor time (time interval between the stimulus and the onset of the EMG burst) and motor time (MT, time interval between the onset of the EMG burst and the mechanical response, which gives access to response execution processes). Electromyogram further permitted to unmask partial errors. Correction ratio was calculated by dividing the number of partial errors by the number of incorrect activations (partial errors + errors). As expected, exercise decreased MT. In addition, exercise reduced the correction ratio. Furthermore, there was a positive inter-subject correlation between these two dependent variables. In line with Servant et al.'s model (2015), we propose that the drop in the efficiency of cognitive control was due to insufficient MT available for action monitoring to operate when incorrect activations were produced.