使用全息希爾伯特頻譜分析法解訊非線性及非穩態的大腦神經活動-以穩態視覺誘發電位為例;Using Holo-Hilbert Spectral Analysis to decipher nonlinear and nonstationary neural activities: an example from steady state visual evoked potentials

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题名:	使用全息希爾伯特頻譜分析法解訊非線性及非穩態的大腦神經活動-以穩態視覺誘發電位為例;Using Holo-Hilbert Spectral Analysis to decipher nonlinear and nonstationary neural activities: an example from steady state visual evoked potentials
作者:	阮鐘堅;Kien, Nguyen Trong
贡献者:	認知與神經科學研究所
关键词:	穩態視覺誘發電位;Steady-state visually evoked potential
日期:	2020-05-05
上传时间:	2020-06-05 17:40:55 (UTC+8)
出版者:	國立中央大學
摘要:	自然界的感覺訊號存在非線性的結構，由訊號的載波頻率及強度的動態變化組成。目前已有許多神經造影及電生理的研究顯示刺激的訊號包絡（signal envelope）對於生存及知覺的重要性。然而，目前對於人類大腦如何處理包絡訊息仍未有完整的暸解，其中最主要的原因是傳統的分析技術未能精確地量化這些訊息。因此，本論文提出新穎的資料分析法，透過分析穩態視覺誘發電位（steady-state visually evoked potential, SSVEP）的訊號包絡來探討大腦訊息處理的神經機制。SSVEP具有穩定及容易測量的特性，因此相當適合用來研究大腦功能的能量頻譜及反應延遲（response latency）。本論文使用發光二極體產生簡單及複雜的視覺刺激來誘發SSVEP，並使用以經驗模態分解（empirical mode decomposition, EMD）為基礎的全息希爾伯特頻譜分析法（Holo-Hilbert spectral analysis, HHSA）來分析不同刺激誘發電位的線性及非線性頻譜特徵。以EMD擷取的訊號包絡為基礎，我進一步發展了包絡相位延遲法來測量從視覺刺激誘發的反應延遲。HHSA的分析結果顯示，複雜LED刺激誘發的SSVEP能夠反映刺激本身的訊號特徵（2赫茲包絡調控14赫茲載波）。除此之外，我亦從HHSA中發現視覺系統對LED刺激的加工：SSVEP的14赫茲載波被4赫茲包絡所調控，同時2赫茲包絡調控的載波頻率涵蓋了從8赫茲到32赫茲的頻段；本研究是第一個報告此現象的文獻。刺激包絡明顯的調控了對於即將進入之訊號的反應。HHSA更有助於比較跨頻率的交互作用及傳統的相位振幅耦合方法。除了能量頻譜外，利用包絡相位延遲法計算從LED刺激呈現到Oz電極記錄到相關電位的反應延遲約為104.55毫秒；在單眼刺激的情況下，優勢眼的反應延遲約為97.14毫秒，而弱勢眼的反應延遲約為104.75毫秒，但兩者差異未達到統計顯著。整體而言，本論文奠定了將HHSA應用於研究大腦活動訊號之非線性特徵及跨頻率交互作用的具體基礎，同時也提供一套嶄新的方法，可用以測量不同腦區間的資訊傳遞.;Natural sensory signals have nonlinear structures dynamically composed of the carrier frequencies and the variation of the amplitude (i.e., envelope). Neuroimaging and electrophysiological studies have demonstrated the envelope stimulus is vital for survival and perception. However, how the human brain processes the envelope information is still poorly understood. It is largely due to the conventional analysis failing to quantify it directly. Hence, this dissertation proposed the novel methods to investigate the underlying neural mechanism of envelope responses collected by Steady-state visually evoked potentials (SSVEPs), which offer reliable and quantitative data to investigate the function of the human brain based on the power spectrum and response latency. The Holo-Hilbert spectral analysis (HHSA), which is a nonlinear analysis tool based on the Empirical Mode Decomposition (EMD), was used to investigate power spectrum of the fundamental and nonlinear features while the envelope-based phase delay method was developed to measure the visual latency. The results of HHSA demonstrate that in addition to the 2 Hz fundamental envelope, 4 Hz amplitude modulation residing in 14 Hz carrier and a broad range of carrier frequencies covering from 8 to 32 Hz modulated by 2 Hz amplitude modulation are also found in the two-dimensional frequency spectrum, which have not yet been recognized before. The envelope of the stimulus is also found to dominantly modulate the response to the incoming signal. Furthermore, the HHSA was also beneficial to investigate the cross-frequency interaction compared to the traditional Phase-amplitude coupling method. Besides the power spectrum, the envelope-based phase delay method shows that the response latency at the occipital lobe (Oz channel) was approximately 104.55 ms for binocular stimulation, and 97.14 ms for the dominant eye and 104.75 ms for the non-dominant eye with no significant difference of response latency between these stimulations. In sum, these findings offer the novel methods for future studies in quantifying the nonlinear features, cross-frequency interaction, and also potentially shed new light on understanding of how long collective neural activities take to travel in the human brain
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