Department of Clinical and Cognitive Neuroscience, Central Institute of Mental Health, University of Heidelberg, Square J5, D-68159 Mannheim, Germany.
Neuroimage. 2010 May 1;50(4):1545-59. doi: 10.1016/j.neuroimage.2010.01.067. Epub 2010 Jan 28.
The steady-state auditory evoked magnetic field was recorded in tinnitus patients and controls, both either musicians or non-musicians, all of them with high-frequency hearing loss. Stimuli were AM-tones with two modulation frequencies and three carrier frequencies matching the "audiometric edge", i.e. the frequency above which hearing loss increases more rapidly, the tinnitus frequency or the frequency 1 1/2 octaves above the audiometric edge in controls, and a frequency 1 1/2 octaves below the audiometric edge. Stimuli equated in carrier frequency, but differing in modulation frequency, were simultaneously presented to the two ears. The modulation frequency-specific components of the dual steady-state response were recovered by bandpass filtering. In both hemispheres, the source amplitude of the response was larger for contralateral than ipsilateral input. In non-musicians with tinnitus, this laterality effect was enhanced in the hemisphere contralateral and reduced in the hemisphere ipsilateral to the tinnitus ear, especially for the tinnitus frequency. The hemisphere-by-input laterality dominance effect was smaller in musicians than in non-musicians. In both patient groups, source amplitude change over time, i.e. amplitude slope, was increasing with tonal frequency for contralateral input and decreasing for ipsilateral input. However, slope was smaller for musicians than non-musicians. In patients, source amplitude was negatively correlated with the MRI-determined volume of the medial partition of Heschl's gyrus. Tinnitus patients show an altered excitatory-inhibitory balance reflecting the downregulation of inhibition and resulting in a steeper dominance hierarchy among simultaneous processes in auditory cortex. Direction and extent of this alteration are modulated by musicality and auditory cortex volume.
稳态听觉诱发磁场被记录在耳鸣患者和对照组中，他们都是高频听力损失患者，包括音乐家和非音乐家。刺激为 AM 音，具有两个调制频率和三个载波频率，与“听阈边缘”匹配，即听力损失增加更快的频率、耳鸣频率或听阈边缘上方 1 个半倍频程的频率，以及听阈边缘下方 1 个半倍频程的频率。在控制组中，载波频率相等但调制频率不同的刺激同时呈现给双耳。通过带通滤波恢复双稳态响应的调制频率特异性分量。在两个半球中，对侧输入的响应源幅度大于同侧输入。在有耳鸣的非音乐家中，这种侧化效应在与耳鸣耳相对侧的半球中增强，在同侧的半球中减弱，特别是对于耳鸣频率。音乐家的半球-输入侧化优势效应小于非音乐家。在两组患者中，源幅度随时间的变化，即幅度斜率，对于对侧输入呈增加趋势，对于同侧输入呈减小趋势。然而，音乐家的斜率小于非音乐家。在患者中，源幅度与内侧 Heschl 回隔板的 MRI 确定体积呈负相关。耳鸣患者表现出兴奋抑制平衡的改变，反映出抑制的下调，导致听觉皮层中同时发生的过程的主导层次更加陡峭。这种改变的方向和程度受音乐性和听觉皮层体积的调节。
