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Analysis of Brain Signals in Response to Transcranial Magnetic Stimulation of Normal Subjects and Subjects with Tinnitus Disorder and Evaluation of its Therapeutic Effect

Sheibani Asl, Nasrin | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52501 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Jahed, Mehran; Mahmoudian, Saeed
  7. Abstract:
  8. According to clinical surveys, it is estimated that chronic tinnitus is experienced by 10 to 15% of the adult population. Tinnitus is defined as the conscious and involuntary perception of noise or ringing without involvement of either mechanical or external audio source. In recent years, a limited number of studies have investigated the effects of applying transcranial magnetic stimulation (TMS) to ameliorate this condition. TMS is a noninvasive intervention in which magnetic pulses are applied by a coil adjacent to the individual's head. In this study, electroencephalogram (EEG) signals are recorded concurrent and as a follow-up to TMS. This makes it possible to study changes caused by magnetic pulses with appropriate temporal resolution.In this regard, based on the previous works on TMS, this study introduces a novel experimental protocol. Furthermore, as the auditory cortex is known to be more active in subjects with tinnitus disorder, very low frequencies are used to modulate the activity of neurons in this region. Therefore, this study considers TMS with a frequency of 0.5 Hz and magnetic field intensity of 110% of motor threshold, applied to the left primary auditory cortex at rest. By recording the evoked potentials induced by the aforementioned stimulation, it is possible to compare temporal responses between healthy and tinnitus individuals in terms of morphology and amplitude range of evoked potentials.In this preliminary and purposeful exploration, the healing effect of TMS on subjects with tinnitus disorder is taken into consideration. In these experiments, 5 patients with tinnitus disorder and 2 healthy individuals were examined in the National Brain Mapping Laboratory, according to the protocol approved by the Ethics Committee of Iran University of Medical Sciences. In this regard, the patients participated in 5 consecutive sessions and healthy individuals participated in one session of EEG recording and TMS. For data evaluation, correlation-based analyses were conducted between the evoked potentials of healthy individuals and the evoked potentials of patients for the first and last sessions. Results indicate a low or even negative correlation between the normal and tinnitus subjects at the first session and a significantly more and positive correlation at the last session after implementation of the proposed protocol. These results are consistent with the reports gathered form the patients, regarding the improvement of their tinnitus symptoms
  9. Keywords:
  10. Transcranial Magnetic Stimulation (TMS) ; Tinnitus ; Electroencephalogram Signals Classification ; Evoked Potential ; Brain Waves

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