Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan Medical School, Ann Arbor, Michigan 48109, Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48105.
J Neurosci. 2013 Dec 11;33(50):19647-56. doi: 10.1523/JNEUROSCI.2788-13.2013.
Tinnitus and cochlear damage have been associated with changes in somatosensory-auditory integration and plasticity in the dorsal cochlear nucleus (DCN). Recently, we demonstrated in vivo that DCN bimodal plasticity is stimulus timing-dependent, with Hebbian and anti-Hebbian timing rules that reflect in vitro spike timing-dependent plasticity. In this in vivo study, we assessed the stimulus timing dependence of bimodal plasticity in a tinnitus model. Guinea pigs were exposed to a narrowband noise that produced a temporary elevation of auditory brainstem response thresholds. A total of 60% of the guinea pigs developed tinnitus as indicated by gap-induced prepulse inhibition of the acoustic startle. After noise exposure and tinnitus induction, stimulus timing-dependent plasticity was measured by comparing responses to sound before and after paired somatosensory and auditory stimulation presented with varying intervals and orders. In comparison with Sham and noise-exposed animals that did not develop tinnitus, timing rules in verified tinnitus animals were more likely to be anti-Hebbian and broader for those bimodal intervals in which the neural activity showed enhancement. Furthermore, units from exposed animals with tinnitus were more weakly suppressed than either Sham animals or exposed animals without tinnitus. The broadened timing rules in the enhancement phase in animals with tinnitus, and in the suppressive phase in exposed animals without tinnitus was in contrast to narrow, Hebbian-like timing rules in Sham animals. These findings implicate alterations in DCN bimodal spike timing-dependent plasticity as underlying mechanisms in tinnitus, opening the way for a therapeutic target.
耳鸣和耳蜗损伤与躯体感觉-听觉整合和背侧耳蜗核(DCN)可塑性的变化有关。最近,我们在体内证明了 DCN 双模态可塑性是刺激定时依赖性的,具有赫布和反赫布定时规则,反映了体外尖峰定时依赖性可塑性。在这项体内研究中,我们评估了耳鸣模型中双模态可塑性的刺激定时依赖性。豚鼠暴露于窄带噪声中,会导致听觉脑干反应阈值暂时升高。总共有 60%的豚鼠出现了耳鸣,表现为声刺激引发的前脉冲抑制。在噪声暴露和耳鸣诱导后,通过比较在不同间隔和顺序下进行体感和听觉刺激对声音的反应,测量刺激定时依赖性可塑性。与未出现耳鸣的 Sham 和噪声暴露动物相比,在验证的耳鸣动物中,那些表现出增强的双模态间隔的定时规则更有可能是反赫布的,且更宽。此外,与 Sham 动物或未出现耳鸣的暴露动物相比,暴露于耳鸣动物的神经元的抑制作用较弱。耳鸣动物增强阶段的定时规则变宽,而未出现耳鸣的暴露动物的抑制阶段的定时规则变窄,与 Sham 动物的赫布样窄定时规则相反。这些发现表明 DCN 双模态尖峰定时依赖性可塑性的改变是耳鸣的潜在机制,为治疗靶点开辟了道路。
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