Muscle Fatigue Affects Mental Simulation of Action

Abstract

Several studies suggest that when subjects mentally rehearse or execute a familiar action, they engage similar neural and cognitive operations. Here, we examined whether muscle fatigue could influence mental movements. Participants mentally and actually performed a sequence of vertical arm movements (rotation around the shoulder joint) before and after a fatiguing exercise involving the right arm. We found similar durations for actual and mental movements before fatigue, but significant temporal discrepancies after fatigue. Specifically, mental simulation was accelerated immediately after fatigue, while the opposite was observed for actual execution. Furthermore, actual movements showed faster adaptation (i.e., return to prefatigue values) than mental movements. The EMG analysis showed that postfatigue participants programmed larger, compared to prefatigue, neural drives. Therefore, immediately after fatigue, the forward model received dramatically greater efferent copies and predicted faster, compared to prefatigue, arm movements. During actual movements, the discrepancy between estimated (forward model output) and actual state (sensory feedback) of the arm guided motor adaptation; i.e., durations returned rapidly to prefatigue values. Since during mental movements there is no sensory information and state estimation derives from the forward model alone, mental durations remained faster after fatigue and their adaptation was longer than those of actual movements. This effect was specific to the fatigued arm because actual and mental movements of the left nonfatigued arm were unaffected. The current results underline the interdependence of motor and cognitive states and suggest that mental actions integrate the current state of the motor system.

Extreme short-term environmental constraints do not update internal models of action as assessed from motor imagery in adults

“…This sensory feedback cannot be applied to IM, therefore they remained unchanged in 0G. This is consistent with a recent study showing that imagined arm movement durations are increased immediately after muscular fatigue and that the durations return to normal prefatigue values after a longer delay than the actual arm movement durations (Demougeot and Papaxanthis, 2011). These authors stated that the delay in adaptation of imagined arm movement durations is the result of the absence of sensory feedback and that state estimation derives from forward model alone, the brain continues to simulate faster mental movements after fatigue based on inappropriate neural drives.…”

Selective Effect of Physical Fatigue on Motor Imagery Accuracy

“…Looking at the selective effect of physical fatigue on IVI and EVI however revealed that both MI duration and vividness were substantially affected when athletes used IVI, whereas there was no actual influence of fatigue when performing EVI. These data suggest that the effect of physical fatigue on MI ability is dependent on imagery content, and might therefore not be due to a general perception of muscular fatigue, as earlier postulated by Demougeot and Papaxanthis [36]. These results further promote the importance of taking the MI perspective into account when studying this mental process.…”

Mental Representation of Arm Motion Dynamics in Children and Adolescents

“…Action representation is generated by an internal forward model, which is a neural network that simulates the dynamic behavior of the body and its interaction with the environment [16], [27], [50], [56]. Theoretically, when participants imagine arm movements, the forward model relates the actual state of the arm (e.g.…”

“…The participants, using their right arm, were requested to actually move or mentally simulate moving (imagined movement) at a natural self-selected speed between the CT and RT or between the CT and LT. Actual and mental trials were performed with eyes open. It is known that relatively long trial durations are necessary to obtain reliable measurements in motor imagery protocols because movement durations have a coarse resolution [16], [50]. Therefore, in our protocol one trial corresponded to three successive and fluid arm movements between the CT and the other targets: CT-RT-CT-RT-CT-RT-CT and CT-LT-CT-LT-CT-LT-CT. For the actual trials, participants were asked to move their arm over the table without touching it.…”