Analysis of brain connectivity through TMS-EEG: A review of current approaches and future directions

Transcranial magnetic stimulation combined with electroencephalography (TMS-EEG) offers a powerful tool to investigate brain connectivity by probing cortical excitability and network dynamics. Current methodologies for connectivity analysis in TMS-EEG include various methodologies to quantify effective connectivity and functional connectivity through the analysis of TMS-evoked potentials (TEP), each capturing distinct features of interareal communication. While effective connectivity approaches quantify signal propagation, they may miss network dynamics revealed by frequency-specific oscillatory patterns relevant for higher-order sensory, motor, and cognitive processes. Functional connectivity metrics applied in TEP analysis can provide deeper insight into state-dependent neural interactions. This narrative review explores current methodologies and recent applications, highlighting their potential and pitfalls, and emphasizing the need for benchmarking to frame their utility in cognitive and clinical neuroscience research.