Vividness and accuracy: Two independent aspects of motor imagery.

Motor imagery is the mental execution of an action without any actual movement. Although numerous studies have utilized questionnaires to evaluate the vividness of motor imagery, it remains unclear whether it is related to the accuracy of motor imagery. To examine the relationship between vividness and accuracy, we investigated brain activity during kinesthetic and visual motor imagery, by using a novel sequential finger-tapping task. We estimated accuracy by measuring the fidelity of the actual performance and evaluated vividness by using a visual analog scale. We found that accuracy of visual motor imagery was correlated with the activity in the left visual cortex, as well as with bilateral sensorimotor regions. In contrast, vividness of visual motor imagery was associated with the activity in the right orbitofrontal cortex. However, there was no correlation in the brain activity between the right orbitofrontal cortex and visuomotor regions or between vividness and accuracy of motor imagery. In addition, we did not find any correlation in the kinesthetic imagery condition. We conclude that vividness of visual motor imagery is associated with the right orbitofrontal cortex and is independent of processes occurring in sensorimotor regions, which would be responsible for the accuracy of visual motor imagery.