基于低温超导量子干涉器件的脑听觉激励磁场探测

Detection of brain auditory evoked magnetic field based on low-T_c superconducting quantum interface device

本文利用磁屏蔽室和二阶轴向梯度计抑制环境磁场噪声,建立了单通道脑磁探测系统,并对不用声音频率下脑听觉激励磁场N100m响应进行了初步探测.结果显示,1000Hz音频和100ms持续声音激励下,N100m峰值的典型强度约为0.4 pT.在低的声音频率激励下,N100m峰出现延时,100 Hz和1000 Hz之间的延时差别达到25 ms.相比于1 kHz特定频率的声音激励,1—4 kHz随机变频下的N100m峰幅度增强,出现了数毫秒的延时.本研究为下一步利用软件梯度计进行多通道脑磁系统和听觉机理研究奠定了一定的基础.

Superconducting quantum interface devices（SQUID） is widely used in human brain signal detection.As one of the applications of magnetoencephalography（MEG） system,the detection of the auditory evoked response is useful for the development of MEG system and the research into auditory mechanism of human brain.Generally,the auditory evoked response includes three peaks which are P50m,N100m and P200m.We develop a single-channel MEG system in a magnetically shielded room based on the superconducting quantum interface device（SQUID） and second-order axial gradiometer.The responses of the main peak N100m under different tone frequencies are preliminarily studied by using our system.The typical evoked response of N100m to 1 kHz pure tone and 100 ms duration is measured to be 0.4 pT.Under the tone stimulus at low frequency,the delay of the peak N100m to the tone onset is 125 ms at 100 Hz,which is longer than the typical value of 100 ms.In comparison with the response to 1 kHz pure tone stimulus,the amplitude of the evoked response in a random frequency range from 1 kHz to 4 kHz is stronger and the delay is several milliseconds.This work lays the foundation of the studies of the auditory mechanism and multichannel MEG system by using software gradiometers.