Interhemispheric Connections Dynamics of Symmetric Cortical Areas According Coherence Analysis of EEG in Therapy-resistant Depressive Patients in Transcranial Magnetic Stimulation

Abstract

The mechanisms of the therapeutic action of TMS, including neurophysiological patterns, remain unclear. The most reasonable tool for identifying neurophysiological changes in depression
can be considered as indicators of coherent analysis (CА) of EEG, reflecting the relationship between certain areas of the cortex in the integrative activity of the brain.
Objectives. The purpose of the study was to determine the dynamics of hemispheric symmetric cortical zones connections in resistant depression patients according to EEG coherent
analysis in TMS course. Methods. The study included 32 patients with treatmentPresistant depression with the severity of symptoms, according to the Hamilton scale (17 items) of at least
20 points (mean 24.7 ± 3.6 points). TMS was performed on a magnetic stimulator “NeuroPMS” on the left dorsolateral prefrontal cortex, 12 sessions of 15 Hz, 100 % of the threshold
intensity. Monopolar EEG was recorded on “NEUROPKM” (Russia) EEG device for topographic mapping of brain electrical activity using the international system of 10–20 %. The control
group consisted of 50 healthy individuals.
Results. To the end of TMS course 20 patients (> 50 % reduction of HAMPD total score) were assigned to the group of responders (R), and the rest (n = 12) consisted of a group of nonP
responders (NR). Comparison of coherent analysis (CA) EEG data values of symmetric cortical zones of the right and left hemispheres of patients with a control group showed that patients
parameter value is lower in all pairs of leads (except occipital), especially between symmetric temporal areas. In relation to the control group of subjects, the average index of coherent analysis
data between the studied pairs of symmetric cortical zones revealed a decrease in the value of CA in P and, even more so, in HP. After TMS course, the magnitude of the average CA value
of P increased, while that of HP decreased even more.
Conclusion. Analysis of the nature of the results obtained in the study can be used not only to clarify data on systemic anomalies of the structure and functions of certain neural networks
and the interaction between them in depressive disorders, but also as predictors of TMS effectiveness.