Dimitrijevic Andrew, Smith Michael L, Kadis Darren S, Moore David R
Otolaryngology-Head and Neck Surgery, Sunnybrook Health Sciences CentreToronto, ON, Canada; Hurvitz Brain Sciences, Evaluative Clinical Sciences, Sunnybrook Research InstituteToronto, ON, Canada; Faculty of Medicine, Otolaryngology-Head and Neck SurgeryUniversity of Toronto, Toronto, ON, Canada.
Communication Sciences Research Center, Cincinnati Children's Hospital Medical CenterCincinnati, OH, USA; Speech and Hearing Sciences, University of WashingtonSeattle, WA, USA.
Front Hum Neurosci. 2017 Feb 24;11:88. doi: 10.3389/fnhum.2017.00088. eCollection 2017.
Understanding speech in noise (SiN) is a complex task involving sensory encoding and cognitive resources including working memory and attention. Previous work has shown that brain oscillations, particularly alpha rhythms (8-12 Hz) play important roles in sensory processes involving working memory and attention. However, no previous study has examined brain oscillations during performance of a continuous speech perception test. The aim of this study was to measure cortical alpha during attentive listening in a commonly used SiN task (digits-in-noise, DiN) to better understand the neural processes associated with "top-down" cognitive processing in adverse listening environments. We recruited 14 normal hearing (NH) young adults. DiN speech reception threshold (SRT) was measured in an initial behavioral experiment. EEG activity was then collected: (i) while performing the DiN near SRT; and (ii) while attending to a silent, close-caption video during presentation of identical digit stimuli that the participant was instructed to ignore. Three main results were obtained: (1) during attentive ("active") listening to the DiN, a number of distinct neural oscillations were observed (mainly alpha with some beta; 15-30 Hz). No oscillations were observed during attention to the video ("passive" listening); (2) overall, alpha event-related synchronization (ERS) of central/parietal sources were observed during active listening when data were grand averaged across all participants. In some participants, a smaller magnitude alpha event-related desynchronization (ERD), originating in temporal regions, was observed; and (3) when individual EEG trials were sorted according to correct and incorrect digit identification, the temporal alpha ERD was consistently greater on correctly identified trials. No such consistency was observed with the central/parietal alpha ERS. These data demonstrate that changes in alpha activity are specific to listening conditions. To our knowledge, this is the first report that shows almost no brain oscillatory changes during a passive task compared to an active task in any sensory modality. Temporal alpha ERD was related to correct digit identification.
理解噪声中的语音（SiN）是一项复杂的任务，涉及感觉编码以及包括工作记忆和注意力在内的认知资源。先前的研究表明，脑振荡，尤其是阿尔法节律（8 - 12赫兹）在涉及工作记忆和注意力的感觉过程中起着重要作用。然而，以前没有研究在连续语音感知测试过程中检查脑振荡情况。本研究的目的是在常用的SiN任务（噪声中的数字，DiN）中，测量专注聆听时的皮层阿尔法节律，以更好地理解在不利聆听环境中与“自上而下”认知处理相关的神经过程。我们招募了14名听力正常（NH）的年轻成年人。在最初的行为实验中测量了DiN语音接收阈值（SRT）。然后收集脑电图（EEG）活动：（i）在接近SRT执行DiN任务时；以及（ii）在呈现参与者被指示忽略的相同数字刺激时，让其观看无声的带字幕视频。获得了三个主要结果：（1）在专注（“主动”）聆听DiN时，观察到一些不同的神经振荡（主要是阿尔法节律，伴有一些贝塔节律；15 - 30赫兹）。在观看视频时（“被动”聆听）未观察到振荡；（2）总体而言，当对所有参与者的数据进行总体平均时，在主动聆听期间观察到中央/顶叶源的阿尔法事件相关同步（ERS）。在一些参与者中，观察到起源于颞叶区域的较小幅度的阿尔法事件相关去同步化（ERD）；以及（3）当根据正确和错误的数字识别对个体EEG试验进行分类时，在正确识别的试验中，颞叶阿尔法ERD始终更大。中央/顶叶阿尔法ERS未观察到这种一致性。这些数据表明阿尔法活动的变化特定于聆听条件。据我们所知，这是第一份报告显示在任何感觉模态中，与主动任务相比，被动任务期间几乎没有脑振荡变化。颞叶阿尔法ERD与正确的数字识别有关。
