Cochlear implantation constitutes a successful therapy of inner ear deafness, with the majority of patients showing good outcomes. There is, however, still some unexplained variability in outcomes with a number of cochlear-implant (CI) users, showing major limitations in speech comprehension. The current study used a multimodal diagnostic approach combining single-photon emission computed tomography (SPECT) and electroencephalography (EEG) to examine the mechanisms underlying speech processing in postlingually deafened CI users (N = 21). In one session, the participants performed a speech discrimination task, during which a 96-channel EEG was recorded and the perfusions marker 99mTc-HMPAO was injected intravenously. The SPECT scan was acquired 1.5 h after injection to measure the cortical activity during the speech task. The second session included a SPECT scan after injection without stimulation at rest. Analysis of EEG and SPECT data showed N400 and P600 event-related potentials (ERPs) particularly evoked by semantic violations in the sentences, and enhanced perfusion in a temporo-frontal network during task compared to rest, involving the auditory cortex bilaterally and Broca’s area. Moreover, higher performance in testing for word recognition and verbal intelligence strongly correlated to the activation in this network during the speech task. However, comparing CI users with lower and higher speech intelligibility [median split with cutoff + 7.6 dB signal-to-noise ratio (SNR) in the Göttinger sentence test] revealed for CI users with higher performance additional activations of parietal and occipital regions and for those with lower performance stronger activation of superior frontal areas. Furthermore, SPECT activity was tightly coupled with EEG and cognitive abilities, as indicated by correlations between (1) cortical activation and the amplitudes in EEG, N400 (temporal and occipital areas)/P600 (parietal and occipital areas) and (2) between cortical activation in left-sided temporal and bilateral occipital/parietal areas and working memory capacity. These results suggest the recruitment of a temporo-frontal network in CI users during speech processing and a close connection between ERP effects and cortical activation in CI users. The observed differences in speech-evoked cortical activation patterns for CI users with higher and lower speech intelligibility suggest distinct processing strategies during speech rehabilitation with CI.

中文翻译：

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脑灌注 SPECT 和 EEG 测量相结合，为具有较高和较低性能的 CI 用户提供不同的语音理解策略

人工耳蜗植入是治疗内耳聋的一种成功方法，大多数患者都取得了良好的效果。然而，许多人工耳蜗 (CI) 用户的结果仍然存在一些无法解释的变异性，显示出言语理解方面的重大局限性。当前的研究使用结合单光子发射计算机断层扫描 (SPECT) 和脑电图 (EEG) 的多模式诊断方法来检查语后耳聋 CI 用户 (N = 21) 的语音处理机制。在一次会议中，参与者执行了一项言语辨别任务，在此期间记录了 96 通道脑电图，并静脉注射了灌注标记物 99mTc-HMPAO。注射后 1.5 小时采集 SPECT 扫描，以测量言语任务期间的皮质活动。第二次治疗包括注射后静息时无刺激的 SPECT 扫描。EEG 和 SPECT 数据分析显示，N400 和 P600 事件相关电位 (ERP) 特别是由句子中的语义违规引起的，并且与休息时相比，任务期间颞额叶网络的灌注增强，涉及双侧听觉皮层和布罗卡区。此外，单词识别和言语智力测试中的较高表现与语音任务期间该网络的激活密切相关。然而，比较具有较低和较高语音清晰度的 CI 用户 [Göttinger 句子测试中截止的中值分割 + 7.6 dB 信噪比 (SNR)] 揭示了具有较高性能的 CI 用户的顶叶和枕叶区域的额外激活，以及那些表现较低的人对上额叶区域的激活更强。此外，SPECT 活动与脑电图和认知能力紧密相关，如 (1) 皮质激活与脑电图、N400（颞叶和枕叶区域）/P600（顶叶和枕叶区域）振幅之间的相关性以及 (2) 皮质之间的相关性所表明。左侧颞叶和双侧枕叶/顶叶区域的激活以及工作记忆能力。这些结果表明 CI 用户在语音处理过程中募集了颞额叶网络，并且 ERP 效应与 CI 用户的皮质激活之间存在密切联系。观察到的具有较高和较低言语清晰度的 CI 用户的言语诱发皮层激活模式差异表明，在 CI 言语康复过程中存在不同的处理策略。