Abstract
AimThe objective of this work was to demonstrate the usefulness of a novel statistical method to study the impact of transcranial magnetic stimulation (TMS) on brain connectivity in patients with depression using different stimulation protocols, i.e., 1 Hz repetitive TMS over the right dorsolateral prefrontal cortex (DLPFC) (protocol G1), 10 Hz repetitive TMS over the left DLPFC (G2), and intermittent theta burst stimulation (iTBS) consisting of three 50 Hz burst bundle repeated at 5 Hz frequency (G3).MethodsElectroencephalography (EEG) connectivity analysis was performed using Directed Transfer Function (DTF) and a set of 21 indices based on graph theory. The statistical analysis of graph-theoretic indices consisted of a combination of the k-NN rule, the leave-one-out method, and a statistical test using a 2 × 2 contingency table.ResultsOur new statistical approach allowed for selection of the best set of graph-based indices derived from DTF, and for differentiation between conditions (i.e., before and after TMS) and between TMS protocols. The effects of TMS was found to differ based on frequency band.ConclusionA set of four brain asymmetry measures were particularly useful to study protocol- and frequency-dependent effects of TMS on brain connectivity.SignificanceThe new approach would allow for better evaluation of the therapeutic effects of TMS and choice of the most appropriate stimulation protocol.
Highlights
Some psychiatric diseases, like depression, may be characterized as dysconnectivity disorders (Friston, 1996; Schmitt et al, 2011)
The application of directional measures, such as Directed Transfer Function (DTF) (Kaminski and Blinowska, 1991), allows for better understanding of the mechanisms involved in neural network re-organization associated with changes in brain states in different conditions among healthy persons or patients suffering from psychiatric disorders
Only one study has applied DTF and graph-theoretic indices to study the effects of Transcranial magnetic stimulation (TMS) on functional connectivity in depression using a standard stimulation protocol, i.e., 10 Hz repetitive TMS applied over the left dorsolateral prefrontal cortex (DLPFC) (Olejarczyk et al, 2020)
Summary
Like depression, may be characterized as dysconnectivity disorders (Friston, 1996; Schmitt et al, 2011). The combination of TMS and electroencephalography (EEG) allows for the non-invasive study of changes in brain connectivity (Shafi and Pascual-Leone, 2012). Recent studies examining connectivity using EEG data recorded in patients with depression have predominantly used non-directional measures (i.e., coherence; Leuchter et al, 2012), various measures of phase synchronization (e.g., Phase-Locking Value; Zuchowicz et al, 2019), Phase Lag Index (Olbrich et al, 2014), Katz’s and Higuchi’s fractal dimensions, and other nonlinear methods or their combinations (Acharya et al, 2015). The application of directional measures, such as Directed Transfer Function (DTF) (Kaminski and Blinowska, 1991), allows for better understanding of the mechanisms involved in neural network re-organization associated with changes in brain states in different conditions among healthy persons or patients suffering from psychiatric disorders. Previous research has shown that the application of 1 Hz rTMS over the right DLPFC causes a shift in frontal alpha power asymmetry toward the right hemisphere (Valiulis et al, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
