腦磁圖儀系統之改進用以進行動物體聽覺刺激之神經活化特性研究

Improvement of Using magnetoencephalography(MEG) as a Sensor Configuration for research of active property in Rats by Auditory Stimulus

黃域思(Yuh-Szu Huang)

指導教授 ： 王立民

國立臺灣大學/理學院/物理學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201800432

摘要

本論文是利用128通道全腦式腦磁圖儀系統進行動物體的聽覺反應。腦磁圖儀是利用超導所製作而成的超導量子干涉元件築構而成，利用其對於磁場量測的高靈敏性，得以量測來自生物體內因為刺激產生神經傳遞的電磁訊號，故對於無論是人文科學以及生物科學相關的研究，都有其助益存在。
由於全腦式腦磁圖儀系統設計上是用於人體腦部訊號的量測，造影後反演算得到的解析度較為受限，訊號源在動物體尚無法精確地表示。因此從前置以及後端運算的部分做改進方可用於較小訊號的量測及演算。
本研究在現有的圖儀系統硬體應用下，進行前置定位校準的修正，試圖較為精確的量測動物體的訊號，將測得的訊號造影成像，利用樣品訊號演算法推得訊號來源的座標。將定位校準改良以及反演算法改善，以用於空間解析度要求較高的動物體。
從觀察聽覺刺激誘發反應的P9波形出現時間以及神經活化的位置，可以知道聽覺刺激從左右耳接收對於活化神經的位置是對稱腦的分佈，但對於誘發反應出現的時間並沒有明顯的影響。
同時利用從等磁場軌跡曲線圖(iso-field contour map)反演算推得ECD(equivalent current dipole)的強度以及位置，比較使用最小範數估計法(minimum-norm estimation, MNE)以及引入參數後並做迭代的最小範數源迭代法(source iteration of minimum norm, SIMN)，可以得到利用SIMN所得的結果較為集中、準確。
最後以線圈陣列測量電流電路之感應磁場模擬未來之磁影像偵測系統，作為發展SQUID陣列磁影像感測系統之前置基礎。

關鍵字

超導 ； 量子穿隧元件 ； 單頻音 ； 腦磁圖儀 ； 等效電流偶極

並列摘要

This study is the use of 128-channel whole brain magnetoencephalography (MEG) for animal auditory response. MEG is built up with superconducting quantum interference devices(SQUIDs) which are made up by superconductors. By using its high sensibility of magnetic measurement, we could use measure the electromagnetic signals generated by biological stimulations of neurotransmission. Therefore, there are merits for both the humanities and bioscience-related researches.
Because the whole brain magnetometer system is designed to measure human brain signals, the resolution obtained after contrast imaging is limited, and the signal source can’t be accurately expressed in the animal body. So the improvement from the front and back-end computing parts is performed for smaller signal measurement and calculation.
In this study, the calibration of the pre-positioning was performed under the existing hardware application of the graph instrument system. In this case, we can measure the signal of the animal body more accurately, image the measured signal and use it to reverse the algorithm coordinates of signal sources. The improvement of the positioning calibration and inversion algorithm is applied for animals which require high spatial resolution.
According to the time of appearance of auditory stimulus-induced P9 waveforms and the location of nerve activation, we can see that the auditory stimulations from the left and right ears reveal symmetrical brain distributions for the activated nerves, and has no obviously different effects on the timing of evoked responses.
Moreover, the intensity and position of the equivalent current dipole(ECD) are deduced from the inversions of the iso-field contour mapping. The minimum-norm estimation (MNE) and the minimum range after introducing the parameters with source iteration of minimum norm (SIMN) are compared. It is found that SIMN can get more concentrated and accurate data than that by using MNE.
On the other hand, the magnetic field induced by a current circuit is measured by the coil arrays to simulate a future magnetic image detection system. This is a preconditioning for the development of a SQUID-array magnetic image sensing system.

並列關鍵字

superconductor ； SQUID ； single tone ； MEG ； equivalent current dipole

參考文獻

1. Lee, Y.H., et al., A whole-head magnetoencephalography system with compact axial gradiometer structure. Superconductor Science & Technology, 2009. 22(4): p. 6.

2. Hamalainen, M., et al., MAGNETOENCEPHALOGRAPHY - THEORY, INSTRUMENTATION, AND APPLICATIONS TO NONINVASIVE STUDIES OF THE WORKING HUMAN BRAIN. Reviews of Modern Physics, 1993. 65(2): p. 413-497.

3. Sally, S.L. and J.B. Kelly, ORGANIZATION OF AUDITORY-CORTEX IN THE ALBINO-RAT - SOUND FREQUENCY. Journal of Neurophysiology, 1988. 59(5): p. 1627-1638.

4. Simpson, G.V. and R.T. Knight, MULTIPLE BRAIN SYSTEMS GENERATING THE RAT AUDITORY EVOKED-POTENTIAL .1. CHARACTERIZATION OF THE AUDITORY-CORTEX RESPONSE. Brain Research, 1993. 602(2): p. 240-250.

5. Lakatos, P., et al., An oscillatory hierarchy controlling neuronal excitability and stimulus processing in the auditory cortex. Journal of neurophysiology, 2005. 94(3): p. 1904-1911.