Department of Clinical and Cognitive Neuroscience, Central Institute of Mental Health, University of Heidelberg, Square J5, D-68159 Mannheim, Germany.
Neuroscience. 2010 May 5;167(2):540-53. doi: 10.1016/j.neuroscience.2010.02.003. Epub 2010 Feb 10.
Amplitude and phase of steady-state signals recorded in response to amplitude-modulated (AM) sine tones vary over time, suggesting that the steady-state response (SSR) reflects not only stimulus input but also its interaction with other input streams or internally generated signals. Alterations of the interaction between simultaneous SSRs associated with tinnitus were studied by recording the magnetic field evoked by AM-tones with one of three carrier and one of three modulation frequencies. Single AM-tones were presented in single presentation mode and superpositions of three AM-tones differing in carrier and modulation frequency in multiple presentation mode. Modulation frequency-specific SSR components were recovered by bandpass filtering. Compared with single mode, in multiple mode SSR amplitude was reduced in healthy controls, but increased in tinnitus patients. Thus, while in controls multiple response components seem to reciprocally inhibit one another, in tinnitus reciprocal facilitation seems to predominate. Reciprocal inhibition was unrelated to the phase coherence among SSR components, but was correlated with the frequency of phase slips, indicating that the lateral interaction among SSR components acts in a quasi-paroxysmal manner and manifests itself in terms of a random train of phase reset events. Phase slips were more frequent in patients than controls both in single and multiple mode. Together, these findings indicate that lateral or surround inhibition of single units in auditory cortex is reduced and suggest that in-field inhibition is increased in tinnitus.
稳态信号的幅度和相位在响应调幅（AM）正弦音时随时间变化，这表明稳态响应（SSR）不仅反映了刺激输入，还反映了其与其他输入流或内部产生的信号的相互作用。通过记录具有三种载波和三种调制频率之一的 AM 音调引起的磁场，研究了与耳鸣相关的同时 SSR 之间相互作用的改变。在单呈现模式下呈现单 AM 音，在多呈现模式下呈现具有不同载波和调制频率的三个 AM 音的叠加。通过带通滤波恢复调制频率特异性 SSR 分量。与单模式相比，在多模式下，健康对照组的 SSR 幅度降低，但耳鸣患者的 SSR 幅度增加。因此，在对照组中，多个响应分量似乎相互抑制，而在耳鸣中，相互促进似乎占主导地位。相互抑制与 SSR 分量之间的相位相干性无关，但与相位滑步的频率相关，这表明 SSR 分量之间的侧向相互作用以准爆发方式起作用，并表现为相位重置事件的随机序列。单模式和多模式下，患者的相位滑步频率均高于对照组。这些发现表明，听觉皮层中单单位的侧向或环绕抑制减少，并表明耳鸣时场内抑制增加。
