Department of Neurobiology, Duke University Medical Center, Durham, NC, USA; Department of Psychology and Neuroscience, Duke University, Durham, NC, USA; Center for Cognitive Neuroscience, Duke University, Durham, NC, USA; Duke Institute for Brain Sciences, Duke University, Durham, NC, USA.
Department of Neurobiology, Duke University Medical Center, Durham, NC, USA; Department of Psychology and Neuroscience, Duke University, Durham, NC, USA; Center for Cognitive Neuroscience, Duke University, Durham, NC, USA; Duke Institute for Brain Sciences, Duke University, Durham, NC, USA.
Hear Res. 2023 Dec;440:108899. doi: 10.1016/j.heares.2023.108899. Epub 2023 Oct 30.
We recently discovered a unique type of otoacoustic emission (OAE) time-locked to the onset (and offset) of saccadic eye movements and occurring in the absence of external sound (Gruters et al., 2018). How and why these eye-movement-related eardrum oscillations (EMREOs) are generated is unknown, with a role in visual-auditory integration being the likeliest candidate. Clues to both the drivers of EMREOs and their purpose can be gleaned by examining responses in normal hearing human subjects. Do EMREOs occur in all individuals with normal hearing? If so, what components of the response occur most consistently? Understanding which attributes of EMREOs are similar across participants and which show more variability will provide the groundwork for future comparisons with individuals with hearing abnormalities affecting the ear's various motor components. Here we report that in subjects with normal hearing thresholds and normal middle ear function, all ears show (a) measurable EMREOs (mean: 58.7 dB SPL; range 45-67 dB SPL for large contralateral saccades), (b) a phase reversal for contra- versus ipsilaterally-directed saccades, (c) a large peak in the signal occurring soon after saccade onset, (d) an additional large peak time-locked to saccade offset and (e) evidence that saccade duration is encoded in the signal. We interpret the attributes of EMREOs that are most consistent across subjects as the ones that are most likely to play an essential role in their function. The individual differences likely reflect normal variation in individuals' auditory system anatomy and physiology, much like traditional measures of auditory function such as auditory-evoked OAEs, tympanometry and auditory-evoked potentials. Future work will compare subjects with different types of auditory dysfunction to population data from normal hearing subjects. Overall, these findings provide important context for the widespread observations of visual- and eye-movement related signals found in cortical and subcortical auditory areas of the brain.
我们最近发现了一种独特的耳声发射（OAE）类型，它与扫视眼动的起始（和结束）时间锁定，并且在没有外部声音的情况下发生（Gruters 等人，2018 年）。这些与眼球运动相关的鼓膜振动（EMREOs）是如何产生的，以及为什么会产生，目前尚不清楚，而它们在视觉-听觉整合中的作用是最有可能的候选者。通过检查正常听力人类受试者的反应，可以获得 EMREOs 驱动因素及其作用的线索。正常听力的所有人都会出现 EMREOs 吗？如果是这样，哪种反应成分最一致？了解 EMREOs 的哪些属性在参与者之间相似，哪些属性更具变异性，将为未来与影响耳朵各个运动成分的听力异常个体进行比较奠定基础。在这里，我们报告在具有正常听力阈值和正常中耳功能的受试者中，所有耳朵都显示出（a）可测量的 EMREOs（平均值：58.7dB SPL；范围为 45-67dB SPL，用于大的对侧扫视），（b）对侧与同侧扫视的相位反转，（c）扫视起始后很快出现信号中的一个大峰值，（d）与扫视结束时间锁定的另一个大峰值，以及（e）表明扫视持续时间编码在信号中的证据。我们将在受试者中最一致的 EMREO 属性解释为最有可能在其功能中发挥重要作用的属性。个体差异可能反映了个体听觉系统解剖结构和生理学的正常变化，就像传统的听觉功能测量一样，如听觉诱发 OAE、鼓室图和听觉诱发电位。未来的工作将比较具有不同类型听觉功能障碍的受试者与正常听力受试者的人群数据。总体而言，这些发现为大脑皮质和皮质下听觉区域中广泛观察到的视觉和眼球运动相关信号提供了重要背景。
