Brandt, I. M. | bioRxiv Science

bioRxiv2024

Ability to monitor deviations of own movement without visual feedback

How conscious sensations of movement relates to signals essential for movement control remains under investigation. This question is typically investigated using visuomotor tasks, in which sensation of movement is disturbed by conflicting visual feedback. The present study uses metacognitive judgements to investigate conscious access to movement signals, unchallenged by visual signals, in an index finger force task. We found that some participants can correctly assign metacognitive judgements (MCJs) to their own force, suggesting that participants do indeed have metacognitive access to sensorimotor signals. We found no correlation between metacognitive access to sensorimotor signal and variance in motor performance. Further, we found that in this purely sensorimotor task, internal focus of attention reduces variability in force compared to external focus of attention. Our results indicate that not only is it possible to access sensorimotor information, it is also possible to use focus of attention to reduce variability in force performance.

neuroscience↗

bioRxiv2024

Evidence of optimal control theory over active inference in corticospinal excitability modulations

Two theories, optimal control theory and active inference, dominate the motor control field. We use transcranial magnetic stimulation (TMS) in force and angle tasks to examine whether corticospinal excitability represents a motor command, as proposed by the optimal control theory, or a proprioceptive prediction, as proposed by active inference. Our results strongly support optimal control theory. We encourage comparisons of the theories against each other based on empirically testable predictions.

neuroscience↗

bioRxiv2024

Force, angle, and velocity parameters of finger movements are reflected in corticospinal excitability

Identifying which movement parameters are reflected in the corticospinal excitability (CSE) will improve our understanding human motor control. Change in CSE measured with transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs) can probe the content of the signal from primary motor cortex (M1) through the corticospinal pathway and spinal motoneurons to the muscle. Here we used MEPs to investigate which movement-related parameters are reflected in CSE in 33 healthy adults. In three separate tasks, we evaluated which movement parameter(s), force, angle, and velocity, are reflected in the MEP amplitude during movement preparation and movement execution. Bayesian model comparison in a forward feature selection framework identified force and velocity measures as reflected in the MEP amplitude during movement preparation, and force, angle, and velocity measures as reflected in the MEP amplitude during movement execution. Importantly, we included measures of electromyography (EMG) in the forward feature selection, and the parameter measures are included only if they add explanatory power of MEP amplitude in addition to the EMG. These findings show that when taking EMG measures into account, all three movement parameters force, angle, and velocity are reflected in CSE. These findings propose a flexible and task-dependent form of signaling in the motor system that allows parameter-specific modulation of CSE to accurately control finger movements. Key pointsO_LIPrior research show that the primary motor cortex activity reflects movement parameters. C_LIO_LIMeasures of the response to a magnetic stimulation, the motor evoked potential (MEP), can be used to assess the content of the signal sent to the muscle. C_LIO_LIWe use Bayesian model comparison to test whether movement parameters are reflected in the models best describing the MEP amplitude modulations. C_LIO_LIWe show that the MEP amplitude reflects all tested movement parameters, force, angle, and velocity. C_LIO_LIOur results indicate a task-dependent form of signaling not only in M1, but also in the corticospinal pathway and spinal motor neurons propagating the signal to the muscle. C_LI

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