Departamento de Neurociencia, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
Programa de Doctorado en Neurociencias, Centro Interdisciplinario de Neurociencia UC, Pontificia Universidad Católica de Chile, Santiago, Chile.
Front Neural Circuits. 2024 Jan 4;17:1301962. doi: 10.3389/fncir.2023.1301962. eCollection 2023.
The mechanisms underlying tinnitus perception are still under research. One of the proposed hypotheses involves an alteration in top-down processing of auditory activity. Low-frequency oscillations in the delta and theta bands have been recently described in brain and cochlear infrasonic signals during selective attention paradigms in normal hearing controls. Here, we propose that the top-down oscillatory activity observed in brain and cochlear signals during auditory and visual selective attention in normal subjects, is altered in tinnitus patients, reflecting an abnormal functioning of the corticofugal pathways that connect brain circuits with the cochlear receptor.
To test this hypothesis, we used a behavioral task that alternates between auditory and visual top-down attention while we simultaneously measured electroencephalogram (EEG) and distortion-product otoacoustic emissions (DPOAE) signals in 14 tinnitus and 14 control subjects.
We found oscillatory activity in the delta and theta bands in cortical and cochlear channels in control and tinnitus patients. There were significant decreases in the DPOAE oscillatory amplitude during the visual attention period as compared to the auditory attention period in tinnitus and control groups. We did not find significant differences when using a between-subjects statistical approach comparing tinnitus and control groups. On the other hand, we found a significant cluster in the delta band in tinnitus when using within-group statistics to compare the difference between auditory and visual DPOAE oscillatory power.
These results confirm the presence of top-down infrasonic low-frequency cochlear oscillatory activity in the delta and theta bands in tinnitus patients, showing that the corticofugal suppression of cochlear oscillations during visual and auditory attention in tinnitus patients is preserved.
耳鸣感知的机制仍在研究中。其中一个假设涉及听觉活动的自上而下处理的改变。在正常听力对照的选择性注意范式中，已经在大脑和耳蜗次声信号中描述了 delta 和 theta 波段的低频振荡。在这里，我们提出，在正常受试者的听觉和视觉选择性注意期间，大脑和耳蜗信号中观察到的自上而下的振荡活动发生改变，反映了连接大脑回路与耳蜗受体的皮质传出途径的异常功能。
为了验证这一假设，我们使用了一种行为任务，在 14 名耳鸣患者和 14 名对照受试者中，该任务在听觉和视觉自上而下的注意力之间交替，同时测量脑电图 (EEG) 和畸变产物耳声发射 (DPOAE) 信号。
我们在控制组和耳鸣组的皮质和耳蜗通道中发现了 delta 和 theta 波段的振荡活动。与听觉注意期相比，在视觉注意期，耳鸣和对照组的 DPOAE 振荡幅度均显著降低。当使用比较耳鸣和对照组的受试者间统计学方法时，我们没有发现显著差异。另一方面，当我们使用组内统计方法比较听觉和视觉 DPOAE 振荡功率之间的差异时，我们发现耳鸣组的 delta 波段存在一个显著的簇。
这些结果证实了耳鸣患者 delta 和 theta 波段存在自上而下的次声低频耳蜗振荡活动，表明耳鸣患者在视觉和听觉注意期间，皮质传出对耳蜗振荡的抑制作用是保留的。
