Kate Godfrey: Resting State fMRI and EEG Functional Connectivity Before and After a Course of rTMS for Major Depressive Disorder
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Thank you for the interesting poster.
Your study describes that rTMS increases theta connectivity, rTMS responders show largest reduction in depression scores and that low theta baseline associated with greater antidepressant response. At the same time baseline theta correlates negatively to depression changes.
Is this study observing a ceiling effect of theta increases on depression scores? And do you think theta baseline could therefore be used to predict responders to both rTMS and Medication? Or do the effects of rTMS and medication differ?
Thanks for your great questions. Firstly, yes the theta results could indicate a ceiling effect of rTMS induced increased connectivity, where those participants with greater capacity for increases demonstrate better outcomes. To answer you second question, baseline theta connectivity may indeed be a good predictor of response to rTMS however this does not mean it will also predict response to medications. While baseline connectivity as a predictor of response to medications was beyond the scope of this work, previous studies have found that EEG predictors of response to medications do not predict response to rTMS, and in fact those predicted to be non-responders to medications have been found to respond better to rTMS. I have included references to these studies below.
Widge, A. S., Avery, D. H., & Zarkowski, P. (2013). Baseline and Treatment-Emergent EEG Biomarkers of Antidepressant Medication Response Do Not Predict Response to Repetitive Transcranial Magnetic Stimulation. Brain Stimulation, 6(6), 929-931. doi: https://doi.org/10.1016/j.brs.2013.05.001
Wu, W., Zhang, Y., Jiang, J., Lucas, M. V., Fonzo, G. A., Rolle, C. E., Etkin, A. (2020). An electroencephalographic signature predicts antidepressant response in major depression. Nature Biotechnology, 38(4), 439-447. doi:10.1038/s41587-019-0397-3