Movable Array of Magnetoencephalography With Optically Pumped Magnetometers Effectively Captures Primary Auditory-Evoked Response Signals in Healthy Populations at Low Altitudes

YUAN Yuan, CHEN Zhengju, SUN Wei, FU Shiqin, JIN Lin, SHENG Jingwei, MENG Qiujian, WU Jiangfen, CHEN Lei, XING H

Abstract


Objective To investigate the effectiveness of a movable (with the distance between the temporal scalp and the detector being adjustable) array of optically pumped magnetometers for magnetoencephalography (OPM-MEG) in capturing auditory evoked response signals in healthy subjects living at low altitudes, and to provide a useful technical reference for subsequent exploration of the changes in brain functions in populations living at high altitudes on a long-term basis.

Methods Forty healthy subjects living at a low altitude (470 m above sea level) were recruited. The distance between the scalp and the bilateral temporal lobe detector was adjusted, and the subjects' auditory responses in the temporal lobes were recorded at the distances of 0 mm, 5 mm, 10 mm, and 15 mm. For the different distances, the M100 peak signal strength, noise, signal-to-noise ratio (SNR), and latency were analyzed along with the corresponding auditory source localization maps. A single-factor analysis of variance was conducted to compare the differences in response signals at varying distances.

Results As the distance between the scalp and the detector increased, the noise, the signal, and the SNR gradually weakened (P<0.001). The noise and signal showed a tendency of linear decline. On the other hand, the SNR reached its maximum at 5 mm and did not show a tendency of linear decline. Latency was not affected by the distance (P=0.72). The results of the auditory stimulus source reconstruction were generally consistent.

Conclusion When the distance between the detector and the scalp is 5 mm, the SNR value is the highest, resulting in high sensitivity and high signal strength. On the other hand, even when the distance between the detector and the scalp reaches 15 mm, the SNR of the OPM-MEG is still higher than 16 dB, which meets the clinical signal acquisition requirements. Furthermore, the auditory stimulus source reconstruction results were generally consistent. Changing the scalp-to-detector distance does not affect the applicability of the source localization results, validating the device's effectiveness in signal acquisition.

 

Keywords: Optically pumped magnetometers, Magnetoencephalography, Distance, Signals, Signal-to-noise ratio

 

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