Continuous theta burst stimulation over the dorsolateral prefrontal cortex improves force steadiness during...

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• The central nervous system relies on internal models and proprioception for motor control without visual feedback.
• The dorsolateral prefrontal cortex (DLPFC) is implicated in motor control and sensorimotor monitoring.
• The causal role of the DLPFC in force steadiness and its dependence on corticospinal excitability are not well understood.

Purpose of the Study:

• To investigate if modulating DLPFC activity via theta burst transcranial stimulation (TBS) affects force steadiness during submaximal contractions without visual feedback.
• To determine if any observed effects on force steadiness are dependent on changes in corticospinal excitability.

Main Methods:

• Twenty-eight healthy volunteers received either continuous TBS (cTBS) or intermittent TBS over the left DLPFC.
• Participants performed a 35% submaximal isometric wrist flexion task without visual feedback.
• Force steadiness (coefficient of variation), motor evoked potentials (MEPs), and maximal voluntary contraction force were measured pre- and post-stimulation.

Main Results:

• Inhibitory cTBS over the left DLPFC significantly improved force steadiness at 15 minutes post-stimulation (P=0.013).
• This improvement in force steadiness occurred without significant changes in MEP amplitudes, maximal voluntary contraction force, or mean submaximal force.
• Facilitatory intermittent TBS did not significantly affect force steadiness.

Conclusions:

• Transient inhibition of the left DLPFC can enhance force steadiness in the absence of visual feedback.
• The observed enhancement in force steadiness was not associated with changes in resting corticospinal excitability.
• These findings suggest the DLPFC plays a role in optimizing sensorimotor integration for motor output stability under limited feedback conditions.