Aperiodic Brain Activity Modulates Corticospinal Excitability

Area of Science:

• Neuroscience
• Computational Neuroscience
• Brain-Computer Interfaces

Background:

• Brain state-dependent transcranial magnetic stimulation (TMS) is a novel neuroregulation technique.
• Estimating cortical excitability using instantaneous power is crucial for time-precise TMS.
• The precise role of instantaneous power, especially aperiodic brain activity, in corticospinal excitability remains unclear.

Purpose of the Study:

• To investigate the influence of instantaneous power, including periodic and aperiodic components, on corticospinal excitability.
• To evaluate the relationship between different power components and motor-evoked potential (MEP) amplitudes.
• To determine how varying TMS intensities affect power-dependent corticospinal excitability.

Main Methods:

• Simultaneous recording of electroencephalography (EEG) and motor-evoked potentials (MEPs) during single-pulse TMS.
• Stimulation of the primary motor cortex at 110% and 120% of resting motor threshold (RMT).
• Analysis of total, periodic, and aperiodic power, including the aperiodic exponent and offset, to assess power dependence.

Main Results:

• Higher alpha and beta power correlated with greater MEP amplitudes.
• The aperiodic component of brain activity demonstrated a more critical role in corticospinal excitability than the periodic component.
• Corticospinal output exhibited less sensitivity to power fluctuations at 120% RMT compared to 110% RMT.

Conclusions:

• Aperiodic brain activity is significantly associated with cortical excitability.
• The aperiodic component may serve as a valuable parameter for refining brain-state-dependent TMS protocols.
• Understanding power dynamics enhances the precision and effectiveness of neurostimulation techniques.