Abstract
A recent theoretical account of motor control proposes that modulation of afferent information plays a role in affecting how readily we can move. Increasing the estimate of uncertainty surrounding the afferent input is a necessary step in being able to move. It has been proposed that an inability to modulate the gain of this sensory information underlies the cardinal symptoms of Parkinson's disease (PD). We aimed to test this theory by modulating the uncertainty of the proprioceptive signal using high‐frequency peripheral vibration, to determine the subsequent effect on motor performance. We investigated if this peripheral stimulus might modulate oscillatory activity over the sensorimotor cortex in order to understand the mechanism by which peripheral vibration can change motor performance. We found that 80 Hz peripheral vibration applied to the right wrist of a total of 54 healthy human participants reproducibly improved performance across four separate randomised experiments on a number of motor control tasks (nine‐hole peg task, box and block test, reaction time task and finger tapping). Improved performance on all motor tasks (except the amplitude of finger tapping) was also seen for a sample of 18PD patients ON medication. EEG data investigating the effect of vibration on oscillatory activity revealed a significant decrease in beta power (15–30 Hz) over the contralateral sensorimotor cortex at the onset and offset of 80 Hz vibration. This finding is consistent with a novel theoretical account of motor initiation, namely that modulating uncertainty of the proprioceptive afferent signal improves motor performance potentially by gating the incoming sensory signal and allowing for top‐down proprioceptive predictions.
Highlights
Every movement we make stimulates peripheral sensory receptors that provide sensory feedback of the motor act
The current study aimed to provide evidence consistent with the hypothesis that increasing proprioceptive uncertainty would lead to improvements on a number of motor control tasks
30 s of 80 Hz peripheral vibration applied to the right wrist of a total of 54 healthy controls reproducibly improved performance related to movement speed across four separate experiments
Summary
Every movement we make stimulates peripheral sensory receptors that provide sensory feedback of the motor act. In order to determine the relevance of any prediction errors, the model requires estimates of both the uncertainty in the motor prediction and the uncertainty of the actual sensory input (Körding & Wolpert, 2004). The importance of the estimate of uncertainty at both of these levels is highlighted in a recent theoretical account of motor control and movement initiation: active inference (Friston, Mattout, & Kilner, 2011). Within this framework increasing the estimate of the uncertainty surrounding the afferent input leads to an attenuation of the sensory signal, which is a necessary step in order to move. We aimed to test one prediction of this theory by modulating the uncertainty of the proprioceptive signal, using high-f requency peripheral vibration, to determine the subsequent effect on motor control
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