Sensory Entrained TMS (seTMS) Enhances Motor Cortex Excitability

Area of Science:

• Neuroscience
• Human Motor Physiology
• Brain Stimulation

Background:

• Transcranial magnetic stimulation (TMS) is vital for studying motor physiology but suffers from response variability.
• This variability stems from mistimed TMS pulses relative to ongoing brain oscillations.
• Optimizing TMS timing is crucial for enhanced mechanistic insights and clinical applications.

Purpose of the Study:

• To introduce and evaluate Sensory Entrained TMS (seTMS), a novel method synchronizing TMS pulses with brain oscillations using musical rhythms.
• To investigate if rhythm-evoked sensorimotor alpha phase alignment enhances primary motor cortex (M1) excitability.
• To assess the impact of seTMS on motor-evoked potentials (MEPs).

Main Methods:

• Electroencephalography (EEG) confirmed that listening to musical rhythms desynchronizes inhibitory sensorimotor rhythms (mu oscillations) approximately 200 ms before auditory events.
• Single TMS pulses were delivered over M1 200 ms before rhythmic auditory stimuli.
• Motor-evoked potentials (MEPs) were recorded to measure M1 excitability.

Main Results:

• Passive listening to rhythms induced predictable desynchronization of sensorimotor alpha oscillations.
• seTMS delivered 200 ms before auditory events resulted in significantly larger MEPs compared to standard TMS and a control condition.
• MEP enhancement via seTMS was independent of musical experience.

Conclusions:

• seTMS effectively enhances corticomotor excitability by precisely timing TMS pulses to brain oscillations.
• This method offers a practical and cost-effective strategy for optimizing non-invasive brain stimulation outcomes.
• seTMS represents a significant advancement in synchronizing brain activity for improved stimulation efficacy.