To go or not to go? Pupillometry elucidates inhibitory mechanisms in motor imagery

ABSTRACT Motor imagery (MI) involves consciously performing an action in our minds without engaging in overt physical movement. Although inhibition is crucial to MI, few studies have explored the nature of inhibitory mechanisms underlying this construct. Therefore, little progress has been made in elucidating how or when inhibition is implemented during MI. The present study addressed this unresolved issue by measuring participants’ pupil dilation (an index of attentional effort) as they performed an inhibitory-control (Go/NoGo) procedure in a modified task-switching paradigm. The results showed that inhibitory mechanisms in MI may be implemented via various routes. When MI was the only movement mode used, minimal attentional effort was invested during the Go/NoGo responses, suggesting an early implemented, proactive inhibitory strategy. Conversely, when imagery was preceded by physical movement responses, inhibition required greater attentional effort and it appears as though more active and attention-demanding inhibitory processes must be employed.