The thalamic medial geniculate body (MGB) is uniquely positioned within the neural tinnitus networks. Deep brain stimulation (DBS) of the MGB has been proposed as a possible novel treatment for tinnitus, yet mechanisms remain elusive. The aim of this study was to characterize neurophysiologic hallmarks in the MGB after noise-exposure and to assess the neurophysiological effects of electrical stimulation of the MGB. Fourteen male Sprague Dawley rats were included. Nine subjects were unilaterally exposed to a 16 kHz octave-band noise at 115 dB for 90 minutes, five received sham exposure. Single units were recorded from the contralateral MGB where spontaneous firing, coefficient of variation, response type, rate-level functions and thresholds were determined. Local field potentials and electroencephalographical (EEG) recordings were performed before and after high frequency DBS of the MGB. Thalamocortical synchronization and power were analyzed. In total, 214 single units were identified (n = 145 in noise-exposed group, n = 69 in control group). After noise-exposure, fast-responding neurons become less- or non-responsive without change to their spontaneous rate, while sustained and suppressed type neurons exhibit enhanced spontaneous activity without change to their stimulus driven activity. MGB DBS suppressed thalamocortical synchronization in the beta and gamma bands, supporting suppression of thalamocortical synchronization as an underlying mechanism of tinnitus suppression by high frequency DBS. These findings contribute to our understanding of the neurophysiologic consequences of noise-exposure and the mechanism of potential DBS therapy for tinnitus.

中文翻译：

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噪声引起的大鼠内侧膝状体的神经生理学改变和深部脑刺激引起的丘脑皮质不同步

丘脑内侧膝状体 (MGB) 位于神经耳鸣网络中的独特位置。MGB 的深部脑刺激 (DBS) 已被提议作为耳鸣的一种可能的新型治疗方法，但机制仍然难以捉摸。本研究的目的是表征暴露于噪声后 MGB 的神经生理学特征，并评估 MGB 电刺激的神经生理学效应。包括十四只雄性 Sprague Dawley 大鼠。九名受试者单方面暴露于 115 dB 的 16 kHz 倍频程噪声中 90 分钟，五名受试者接受假暴露。从对侧 MGB 记录单个单元，其中确定了自发放电、变异系数、反应类型、速率水平函数和阈值。在 MGB 的高频 DBS 之前和之后进行局部场电位和脑电图 (EEG) 记录。分析了丘脑皮质同步和功率。总共确定了 214 个单个单元（噪声暴露组 n = 145，对照组 n = 69）。在噪声暴露后，快速反应神经元变得反应减弱或无反应，其自发率没有变化，而持续和抑制型神经元表现出增强的自发活动，而不会改变其刺激驱动的活动。MGB DBS 抑制了 β 和 γ 波段的丘脑皮质同步，支持抑制丘脑皮质同步作为高频 DBS 抑制耳鸣的潜在机制。