Schoonhoven R, Boden C J R, Verbunt J P A, de Munck J C
Department of ENT/Audiology, Leiden University Medical Centre, Leiden, The Netherlands.
Clin Neurophysiol. 2003 Nov;114(11):2096-106. doi: 10.1016/s1388-2457(03)00200-1.
The amplitude-modulation-following response (AMFR) is the frequency component detectable in the electroencephalogram (EEG) or magnetoencephalography (MEG) corresponding to the modulation frequency of an amplitude modulated tone used as a continuous acoustic stimulus. Various properties of the AMFR depend on modulation frequency, suggesting that different generators along the auditory pathway are involved. The present study addresses these issues on the basis of a whole head MEG experiment.
AM tones with modulators in the 40 Hz and 80 Hz range were presented unilaterally to 10 normal hearing subjects. Biomagnetic responses were recorded with a 151 channel MEG system. The data analysis concentrated on the phase coherence of the responses, group delays and the estimated location of underlying equivalent dipole sources.
MEG AMFR is more reliably detected in the 40 Hz than in the 80 Hz range. Both response amplitude and phase coherence indicate clear bilateral activation over the parietal/temporal region. Dipole source analysis confirms that sources are located in or near the auditory cortex. Group delays at 80 Hz are shorter than at 40 Hz.
In both modulation frequency ranges MEG responses are dominated by activity in the auditory cortex, in apparent contrast with EEG data in the literature, pointing to dominant contributions of thalamic sources to the 80 Hz AMFR.
调幅跟随反应（AMFR）是在脑电图（EEG）或脑磁图（MEG）中可检测到的频率成分，它对应于用作连续听觉刺激的调幅音的调制频率。AMFR的各种特性取决于调制频率，这表明听觉通路上不同的发生器参与其中。本研究基于全脑MEG实验探讨这些问题。
向10名听力正常的受试者单侧呈现调制频率在40Hz和80Hz范围内的调幅音。使用151通道MEG系统记录生物磁反应。数据分析集中在反应的相位相干性、群延迟以及潜在等效偶极子源的估计位置。
在40Hz范围内比在80Hz范围内更可靠地检测到MEG AMFR。反应幅度和相位相干性均表明在顶叶/颞叶区域有明显的双侧激活。偶极子源分析证实源位于听觉皮层内或其附近。80Hz时的群延迟比40Hz时短。
在两个调制频率范围内，MEG反应均以听觉皮层的活动为主，这与文献中的EEG数据明显不同，文献中的EEG数据表明丘脑源对80Hz AMFR有主要贡献。
