| dc.description.abstract | The relationship between Motor Imagery (MI) and Motor Execution (ME) has been debated for a long time. The functional equivalence hypothesis asserts identical operating principles underlying motor imagery and motor execution. However, diverse motor tasks have been adopted in the extant literature and inconsistent findings reported. The current study aims to examine the modulating factors of functional equivalence as well as to design objective methods that can better quantify motor imagery. In Experiment 1, isometric force production with minimal spatial kinesthetic movements were adopted to explore how spatial (where) or non-spatial (what) visual information modulate the linear function between task loading and imagery/execution duration. While the functional equivalence predicts identical linear functions for MI and ME, the results indicated deeper slope for the ME than the MI condition for both “where” and “what” feedback groups. The estimation of imagery/execution duration in the Experiment 1 heavily relied on self-report, which may be contaminated by the execution state and task demand. In Experiment 2 and 3, an objective experimental paradigm for assessing MI, the repetition effect, which shows the repeated response is faster than non-repeated ones in ME, was adopted to examine functional equivalence. In Experiment 2, participants were instructed to imagine or execute manual speeded-choices indicated by consecutively presented pairs of visual prime and probe, and reaction times (RT) to probes were compared between trial pairs that required repeated or non-repeated responses to the prime and probe, respectively. Significant repetition effect in both Execution and Imagery conditions (though weaker in the latter) were found, but not in the Perception condition where participants simply observed the prime without executing or imagining responses. In Experiment 3, the mental simulation duration of the Imagery was prolonged to allow sufficient time for completing mental simulation and the electromyography (EMG) activation was controlled. There was still stronger repetition effect in the Execution than the Imagery condition, but repetition effect in Imagery and Execution were not correlated. Taken together, through a novel paradigm which measures motor imagery in a more explicit and objective fashion than conventional methods, we argued that motor imagery is not functionally equivalent to execution. On the basis of the new paradigm, future studies with brain dynamic measures may help to further specify the exact neural mechanisms shared by or distinguishing motor imagery and execution. | en_US |