Theta-burst stimulation: remote physiological and local behavioral after-effects.

Area of Science:

• Neuroscience
• Motor Control
• Brain Stimulation

Background:

• Theta-burst stimulation (TBS) is a novel repetitive transcranial magnetic stimulation (TMS) protocol.
• TBS can suppress motor-evoked potentials (MEPs) in the contralateral motor cortex.
• The effects of TBS on distant connected brain sites and force control are not well understood.

Purpose of the Study:

• To investigate the effects of TBS on motor cortical excitability when applied to motor cortex and connected brain regions.
• To determine if TBS induces measurable changes in force control.
• To explore the duration of TBS-induced physiological and behavioral changes.

Main Methods:

• Subjects received TBS (TBS-300 or TBS-600) over the left motor cortex (M1(LEFT)) or other brain regions.
• Motor cortical excitability was assessed using MEPs in the abductor pollicis brevis (APB) muscle.
• Force control was evaluated during an isometric thumb abduction task.

Main Results:

• TBS over motor cortices reduced contralateral MEP amplitude and increased ipsilateral MEP amplitude.
• TBS over the dorsal premotor cortex (PMd) or mid-occipital (MO) regions did not alter MEPs.
• Force control was impaired for at least 5 minutes after TBS over the left motor cortex.

Conclusions:

• TBS applied to motor cortices induces changes in corticospinal excitability.
• TBS can impair fine motor control, specifically force level control.
• TBS may have remote physiological effects and reveals local functional properties of stimulated brain regions.