Subcortical sources dominate the neuroelectric auditory frequency-following response to speech
Subcortical sources dominate the neuroelectric auditory frequency-following response to speech
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DOI：
10.1016/j.neuroimage.2018.03.060
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发表时间：
2018-07-15
期刊：
影响因子：
5.7
通讯作者：
Bidelman, Gavin M.
中科院分区：
文献类型：
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作者：
Bidelman, Gavin M.
频率跟随响应（FFR）是神经音电位，其提供进入复杂声音编码的窗口（例如，语音/音乐）、听觉障碍和神经可塑性。虽然FFR的神经起源仍存在争议，但在证明通过脑磁图（MEG）记录的FFR由皮质而不是之前假设的脑干结构主导后，重新出现了争议。在这里，我们通过EEG记录了高密度（64 ch）FFR，并将最先进的源成像技术应用于多通道数据（离散偶极子建模、分布式成像、独立分量分析、计算模拟）。我们的数据证实了混合发电机定位于双侧听神经（AN），脑干下丘（BS），和双边初级听觉皮层（PAC）。然而，对源波形的频率特异性检查显示，这些核对总FFR的相对贡献在刺激频率之间变化。而AN和BS源产生高达类似于700 Hz的稳健FFR，PAC显示出弱锁相，其中在语音基频（100 Hz）以上具有很少的FFR能量。值得注意的是，FXR A成像进一步显示，对于FFR> 150 Hz，PAC激活被根除，高于150 Hz，仅皮质下源保持活跃。我们的研究结果表明：（i）血流储备分数产生的部位随刺激频率的变化而变化;（ii）与MEG中观察到的模式相反，皮层下结构对电记录的血流储备分数的贡献最大（AN >= BS > PAC）。我们推断，在之前的神经磁数据中观察到的皮质优势可能是由于MEG对浅表脑组织的偏倚，低估了驱动大部分语音FFR的皮质下结构。通过确保刺激频率> 150-200 Hz，高于皮层神经元的锁相极限，可以实现将皮层下FFR与皮层FFR完全分离。
Frequency-following responses (FFRs) are neurophonic potentials that provide a window into the encoding of complex sounds (e.g., speech/music), auditory disorders, and neuroplasticity. While the neural origins of the FFR remain debated, renewed controversy has reemerged after demonstration that FFRs recorded via magnetoencephalography (MEG) are dominated by cortical rather than brainstem structures as previously assumed. Here, we recorded high-density (64 ch) FFRs via EEG and applied state-of-the art source imaging techniques to multichannel data (discrete dipole modeling, distributed imaging, independent component analysis, computational simulations). Our data confirm a mixture of generators localized to bilateral auditory nerve (AN), brainstem inferior colliculus (BS), and bilateral primary auditory cortex (PAC). However, frequency-specific scrutiny of source waveforms showed the relative contribution of these nuclei to the aggregate FFR varied across stimulus frequencies. Whereas AN and BS sources produced robust FFRs up to similar to 700 Hz, PAC showed weak phase-locking with little FFR energy above the speech fundamental (100 Hz). Notably, CLARA imaging further showed PAC activation was eradicated for FFRs > 150 Hz, above which only subcortical sources remained active. Our results show (i) the site of FFR generation varies critically with stimulus frequency; and (ii) opposite the pattern observed in MEG, subcortical structures make the largest contribution to electrically recorded FFRs (AN >= BS > PAC). We infer that cortical dominance observed in previous neuromagnetic data is likely due to the bias of MEG to superficial brain tissue, underestimating subcortical structures that drive most of the speech-FFR. Cleanly separating subcortical from cortical FFRs can be achieved by ensuring stimulus frequencies are > 150-200 Hz, above the phase-locking limit of cortical neurons.