Section of Biomagnetism, Department of Neurology, Heidelberg University Hospital, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.
Section of Biomagnetism, Department of Neurology, Heidelberg University Hospital, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.
Neuroimage Clin. 2022;36:103188. doi: 10.1016/j.nicl.2022.103188. Epub 2022 Sep 10.
In single-sided deafness patients fitted with a cochlear implant (CI) in the affected ear and preserved normal hearing in the other ear, acoustic and electric hearing can be directly compared without the need for an external control group. Although poor pitch perception is a crucial limitation when listening through CIs, it remains unclear how exactly the cortical processing of pitch information differs between acoustic and electric hearing. Hence, we separately presented both ears of 20 of these patients with vowel sequences in which the pitch contours were either repetitive or variable, while simultaneously recording functional near-infrared spectroscopy (fNIRS) and EEG data. Overall, the results showed smaller and delayed auditory cortex activity in electric hearing, particularly for the P2 event-related potential component, which appears to reflect the processing of voice pitch information. Both the fNIRS data and EEG source reconstructions furthermore showed that vowel sequences with variable pitch contours evoked additional activity in posterior right auditory cortex in electric but not acoustic hearing. This surprising discrepancy demonstrates, firstly, that the acoustic detail transmitted by CIs is sufficient to distinguish between speech sounds that only vary regarding their pitch information. Secondly, the absence of a condition difference when stimulating the normal-hearing ears suggests a saturation of cortical activity levels following unilateral deafness. Taken together, these results provide strong evidence in favour of using CIs in this patient group.
在单侧聋患者中，在受影响的耳朵中植入人工耳蜗（CI），而在另一只耳朵中保留正常听力，可以直接比较声学和电听觉，而无需外部对照组。虽然通过人工耳蜗聆听时，较差的音高感知是一个关键的限制，但皮质处理音高信息的方式在声学和电听觉之间究竟有何不同仍不清楚。因此，我们分别向 20 名患者的双耳呈现了具有重复或可变音高轮廓的元音序列，同时记录功能近红外光谱（fNIRS）和脑电图（EEG）数据。总的来说，结果显示电听觉中的听觉皮层活动较小且延迟，特别是对于 P2 事件相关电位成分，这似乎反映了语音音高信息的处理。fNIRS 数据和 EEG 源重建都表明，在电听觉中，具有可变音高轮廓的元音序列会在右后听觉皮层中引起额外的活动，但在声学听觉中则不会。这种令人惊讶的差异首先表明，CI 传输的声学细节足以区分仅在音高信息上有所不同的语音。其次，当刺激正常听力耳朵时没有出现条件差异，这表明单侧耳聋后皮质活动水平达到饱和。总之，这些结果为在该患者群体中使用 CI 提供了有力的证据。
