Tracking causal pathways in TMS-evoked brain responses

Area of Science:

• Neuroscience
• Systems Neuroscience
• Computational Neuroscience

Background:

• Understanding brain network dynamics is crucial for deciphering causal mechanisms.
• Transcranial magnetic stimulation (TMS) combined with electroencephalography (EEG) allows high-temporal-resolution tracking of brain responses.
• Investigating neurobiological mechanisms of TMS treatment response requires network-level insights.

Purpose of the Study:

• To propose a quantitative framework for inferring causal pathways in TMS-evoked brain responses.
• To explore how local perturbations in cortical activity propagate across the brain network.
• To gain network-level insights into the neurobiological mechanisms underlying TMS treatment response.

Main Methods:

• Utilized a concurrent combination of TMS and EEG.
• Developed a quantitative framework integrating sparse non-negative matrix factorization and stage-dependent effective connectivity.
• Inferred causal pathways from TMS-evoked brain activity.

Main Results:

• Single-pulse TMS initially induced local activity in the stimulated region (left primary motor cortex, M1).
• Activity propagated to the contralateral hemisphere and other brain regions.
• A feedback loop was observed, with activity returning from the contralateral region (right M1) to the stimulation region (left M1).

Conclusions:

• Local perturbations propagate through brain networks, influencing various cortical regions.
• The study offers insights into the neural mechanisms of TMS-evoked brain responses from a network perspective.
• Preliminary evidence demonstrates the utility of the proposed framework for understanding brain network dynamics.