Time-frequency analysis in EEG for the Treatment of Major Depressive Disorder Using rTMS

Mehran Nikravan1Elias Ebrahimzadeh2

۱ Brain and Cognition Clinic Cognitive science inistute, Tehran, Iran

۲CIPCE, School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran

Transcranial Magnetic Stimulation (TMS) is defined as a non-invasive technique of brain stimulation conducted for both diagnostic and therapeutic purposes. TMS can effectively excite the brain neurons and increase the brain plasticity which comes particularly useful in psychiatric and neurological fields. This research has looked into different electroencephalograph (EEG) frequency bands: alpha (8–۱۳ Hz), beta (15–۳۰ Hz), gamma (30–۱۰۰ Hz), theta (4–۷ Hz) and delta (0.5-4 Hz) before and after using a novel TMS device, which is designed to create a high current pulse generator on the transducer. We have demonstrated the overall design process of our TMS device as well as the effects of the new Major Depression Disorder (MDD) protocol in 5 days in each week and a total of 3 weeks on 31 cases including normal people and patients with different levels of depression severity differentiated based on the Beck depression inventory and by processing the EEG signals and time-frequency analysis. We then go on to compare the participants’ depression severity before, after and 2 months after finishing the last treatment session using the proposed TMS. Absolute Power (AP), Band Powers (BP), Theta and Beta Bands Entropies (BA), which were extracted from the EEG, as well as nonlinear methods are used as features for the classification of changes in patient and normal cases after applying the new TMS. Finally, to evaluate the outcome of the treatment procedures, in which the proposed TMS has been implemented, we used different classifiers such as Support Vector Machine (SVM) and Artificial Neural Network (ANN). Accordingly, we can go beyond the Beck score and clinically classify the EEG signal into two classes of depression and normal. The results showed significant changes in left prefrontal cortex of brain activities in medication-resistance patients after 3 weeks of applying the proposed TMS. Also, the electrophysiological changes are shown to be evident in patients with major depression