Examining and Modulating Neural Circuits in Psychiatric Disorders With Transcranial Magnetic Stimulation and Electroencephalography: Present Practices and Future Developments

Abstract

Transcranial magnetic stimulation (TMS) is a noninvasive brain stimulation technique uniquely equipped to both examine and modulate neural systems and related cognitive and behavioral functions in humans. As an examination tool, TMS can be used in combination with EEG (TMS-EEG) to elucidate directly, objectively, and noninvasively the intrinsic properties of a specific cortical region, including excitation, inhibition, reactivity, and oscillatory activity, irrespective of the individual's conscious effort. Additionally, when applied in repetitive patterns, TMS has been shown to modulate brain networks in healthy individuals, as well as ameliorate symptoms in individuals with psychiatric disorders. The key role of TMS in assessing and modulating neural dysfunctions and associated clinical and cognitive deficits in psychiatric populations is therefore becoming increasingly evident. In this article, the authors review TMS-EEG studies in schizophrenia and mood disorders, as most TMS-EEG studies to date have focused on individuals with these disorders. The authors present the evidence on the efficacy of repetitive TMS (rTMS) and theta burst stimulation (TBS), when targeting specific cortical areas, in modulating neural circuits and ameliorating symptoms and abnormal behaviors in individuals with psychiatric disorders, especially when informed by resting-state and task-related neuroimaging measures. Examples of how the combination of TMS-EEG assessments and rTMS and TBS paradigms can be utilized to both characterize and modulate neural circuit alterations in individuals with psychiatric disorders are also provided. This approach, along with the evaluation of the behavioral effects of TMS-related neuromodulation, has the potential to lead to the development of more effective and personalized interventions for individuals with psychiatric disorders.

Keywords: Bipolar Disorder; Depressive Disorders; EEG; Neurophysiology; Neurostimulation; Psychotic Disorders; Schizophrenia; Transcranial Magnetic Stimulation.

Figure 1.. Transcranial Magnetic Stimulation (TMS) as a tool to examine and modulate human brain circuits.

TMS paradigms (single pulse, paired pulse, repetitive TMS) and procedures (number of stimuli, interstimulus interval), goals (probing or modulating) and method (collecting TMS-evoked EEG potentials, or TEPs), brain mechanisms (local and global activity, excitation, inhibition, oscillatory activity, and connectivity), and measurable TEPs output (GMFP, LMFP, TEPs amplitude, ERSP, ITC, NF, SCD, and SCS) are presented.