本研究藉由多通道的腦磁波儀記錄穩態聽性誘發之腦磁波，來探討耳鳴患者在接受規律聲音刺激時大腦神經活化的能量變化與正常人之差異。本研究在台北榮民總醫院收取共10位受測者(5名耳鳴患者、單耳耳鳴)，年齡介於22到50歲（平均年齡33歲），皆為右撇子。MEG實驗在具有磁場遮蔽效應(magnetically shielded) 與噪音屏蔽的檢查室中進行，取樣頻率為1000Hz。實驗分別對左耳及右耳做刺激，受試者先做純音刺激實驗，確保受測者聽力在可接受範圍之內，再做穩態聲音刺激實驗，刺激聲音材料使用帶有37Hz 調變之1000Hz聲頻。我們將MEG收取的資料使用經驗模態分解法拆成數個IMF，並把每個IMF作頻譜轉換，挑選含有誘發資訊(37Hz)的IMF做觀察。我們發現正常人的穩態聽覺誘發有以下幾種情形：1.右半腦能量總是大於左半腦、2.對側耳刺激時能量較強。耳鳴患者與正常人對比則沒有上述兩條規律，我們猜測與耳鳴造成大腦皮質可塑性(plasticity)的不正常放電有關，另外從大腦皮質的誘發之區域比正常人廣泛，則可推測因為耳鳴使得某些大腦神經元壞死，進而引發周圍大腦的過度補償之可能。This dissertation adopted multi-channel MEG to study the steady-state auditory evoked field (SSAEF) responses in tinnitus patients. In this study, 10 right-handed subjects (5 single-side tinnitus patients), aged from 22 to 50 years (mean age at 33 years) were recruited. MEG experiments were performed in a sound-proof magnetic shielding room. MEG data were recorded at 1000 Hz sampling rate. Auditory stimuli were given to subject’s left ear and right ear separately. Preceding the SSAEF study, pure tone stimulations were given to each subject to ensure the sound loudness was within subject’s acceptable range. The stimulation material of SSAEF was 1000Hz sound modulated by 37 Hz modulation frequency. MEG data were segmented into epochs and decomposed by empirical mode decomposition (EMD) into several intrinsic mode functions (IMF). Task-related IMFs with 37Hz information were identified to reconstruct noise-suppressed SSAEFs. In this study, we found the SSAEFs have the following characteristics in normal subjects: 1. right brain energy is always greater than the left hemisphere, and 2. Greater responses induced by contralateral auditory stimulation. Neverthelss, no similar finding was concluded in tinnitus patients. We guess it is caused by cerebral cortex plasticity, it makes the brain not normal discharge. And We also found disinhibition of SSAEF response in affected side (tinntus ear), it might caused by the some reason.
