Department of Cognitive Neuroscience, Maastricht University, Maastricht, the Netherlands; The Brain and Mind Institute, University of Western Ontario, 1151 Richmond St. N., London, ON N6A 5B7, Canada.
Cochlear Benelux NV, Mechelen Campus - Industrie Noord, Schaliënhoevedreef 20, Building I, Mechelen B-2800, Belgium.
Neuroimage Clin. 2020;25:102166. doi: 10.1016/j.nicl.2020.102166. Epub 2020 Jan 11.
Tinnitus is a clinical condition defined by hearing a sound in the absence of an objective source. Early experiments in animal models have suggested that tinnitus stems from an alteration of processing in the auditory system. However, translating these results to humans has proven challenging. One limiting factor has been the insufficient spatial resolution of non-invasive measurement techniques to investigate responses in subcortical auditory nuclei, like the inferior colliculus and the medial geniculate body (MGB). Here we employed ultra-high field functional magnetic resonance imaging (UHF-fMRI) at 7 Tesla to investigate the frequency-specific processing in sub-cortical and cortical regions in a cohort of six tinnitus patients and six hearing loss matched controls. We used task-based fMRI to perform tonotopic mapping and compared the magnitude and tuning of frequency-specific responses between the two groups. Additionally, we used resting-state fMRI to investigate the functional connectivity. Our results indicate frequency-unspecific reductions in the selectivity of frequency tuning that start at the level of the MGB and continue in the auditory cortex, as well as reduced thalamocortical and cortico-cortical connectivity with tinnitus. These findings suggest that tinnitus may be associated with reduced inhibition in the auditory pathway, potentially leading to increased neural noise and reduced functional connectivity. Moreover, these results indicate the relevance of high spatial resolution UHF-fMRI for the investigation of the role of sub-cortical auditory regions in tinnitus.
耳鸣是一种临床病症，其定义为在没有客观声源的情况下听到声音。早期的动物模型实验表明，耳鸣源于听觉系统处理方式的改变。然而，将这些结果转化到人类身上一直具有挑战性。其中一个限制因素是，非侵入性测量技术的空间分辨率不足以研究下丘脑中核和内侧膝状体等皮质下听觉核团的反应。在这里，我们采用 7 特斯拉超高场功能磁共振成像 (UHF-fMRI) 技术，对六名耳鸣患者和六名听力损失匹配对照组的皮质下和皮质区域进行了频率特异性处理的研究。我们使用基于任务的 fMRI 进行音调映射，并比较了两组之间频率特异性反应的幅度和调谐。此外，我们还使用静息态 fMRI 来研究功能连接。我们的结果表明，耳鸣患者的频率调谐选择性出现了频率非特异性降低，这种降低始于膝状体核水平，并在听觉皮层中持续存在，同时还伴有丘脑皮质和皮质皮质连接的减少。这些发现表明，耳鸣可能与听觉通路中抑制作用的减弱有关，这可能导致神经噪声增加和功能连接减少。此外，这些结果表明，高空间分辨率 UHF-fMRI 对于研究皮质下听觉区域在耳鸣中的作用具有重要意义。
