The influence of eye movements on the temporal features of executed and imagined arm movements

The very close coordination between eye and hand indicates that eye movements are parts of the neural processes underlying the planning and control of arm movements. Eye movements are fundamental during observed actions and play a functional role in visual mental imagery. However, the role of eye movements during imagined actions is still unknown. Here, we report the timing features of eye and arm pointing movements for nine healthy participants in four conditions: Executed movements with orientation saccades (Eyes Free) or with no saccades (Eyes Motionless), and Imagined movements with Eyes Free or with Eyes Motionless. The first result was a facilitation effect of saccades upon both executed and imagined arm movements as revealed by the shorter arm movement durations in Eyes Free than in Eyes Motionless. Another interesting finding was that executed and imagined movements preserved their temporal similarities in both Eyes Free and Eyes Motionless, suggesting that the accuracy of motor representations is not dependent on the presence or lack of eye movements. This result and the close similarities between the EOG patterns accompanying both executed and imagined arm pointing movements in Eyes Free, argue in favour of a similar neurocognitive network in executed and imagined actions. We propose that internal forward models provide fine estimations of the temporal features of imagined arm movements, whatever they accompanied, or not, by orientation saccades.