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Parametric Cognitive Load Reveals Hidden Costs in the Neural Processing of Perfectly Intelligible Degraded Speech
Journal of Neuroscience ( IF 5.3 ) Pub Date : 2022-06-08 , DOI: 10.1523/jneurosci.1777-21.2022
Harrison Ritz 1, 2 , Conor J Wild 3 , Ingrid S Johnsrude 3, 4
Affiliation  

Speech is often degraded by environmental noise or hearing impairment. People can compensate for degradation, but this requires cognitive effort. Previous research has identified frontotemporal networks involved in effortful perception, but materials in these works were also less intelligible, and so it is not clear whether activity reflected effort or intelligibility differences. We used functional magnetic resonance imaging to assess the degree to which spoken sentences were processed under distraction and whether this depended on speech quality even when intelligibility of degraded speech was matched to that of clear speech (close to 100%). On each trial, male and female human participants either attended to a sentence or to a concurrent multiple object tracking (MOT) task that imposed parametric cognitive load. Activity in bilateral anterior insula reflected task demands; during the MOT task, activity increased as cognitive load increased, and during speech listening, activity increased as speech became more degraded. In marked contrast, activity in bilateral anterior temporal cortex was speech selective and gated by attention when speech was degraded. In this region, performance of the MOT task with a trivial load blocked processing of degraded speech, whereas processing of clear speech was unaffected. As load increased, responses to clear speech in these areas declined, consistent with reduced capacity to process it. This result dissociates cognitive control from speech processing; substantially less cognitive control is required to process clear speech than is required to understand even very mildly degraded, 100% intelligible speech. Perceptual and control systems clearly interact dynamically during real-world speech comprehension.

SIGNIFICANCE STATEMENT Speech is often perfectly intelligible even when degraded, for example, by background sound, phone transmission, or hearing loss. How does degradation alter cognitive demands? Here, we use fMRI to demonstrate a novel and critical role for cognitive control in the processing of mildly degraded but perfectly intelligible speech. We compare speech that is matched for intelligibility but differs in putative control demands, dissociating cognitive control from speech processing. We also impose a parametric cognitive load during perception, dissociating processes that depend on tasks from those that depend on available capacity. Our findings distinguish between frontal and temporal contributions to speech perception and reveal a hidden cost to processing mildly degraded speech, underscoring the importance of cognitive control for everyday speech comprehension.



中文翻译:

参数认知负荷揭示了完全可理解的退化语音的神经处理中的隐藏成本

言语通常会因环境​​噪音或听力障碍而降低。人们可以补偿退化,但这需要认知努力。先前的研究已经确定了参与努力感知的额颞叶网络,但这些作品中的材料也不太容易理解,因此尚不清楚活动是否反映了努力或可理解性差异。我们使用功能性磁共振成像来评估在分心的情况下口语句子的处理程度,以及这是否取决于语音质量,即使降级语音的清晰度与清晰语音的清晰度相匹配(接近 100%)。在每次试验中,男性和女性人类参与者要么听一个句子,要么听一个并发的多对象跟踪 (MOT) 任务,该任务会施加参数认知负荷。双侧前岛叶的活动反映了任务要求;在 MOT 任务期间,活动随着认知负荷的增加而增加,而在语音聆听期间,活动随着语音变得更加退化而增加。与此形成鲜明对比的是,双侧前颞叶皮层的活动具有语言选择性,并且在语言退化时受到注意力的限制。在该区域中,具有微不足道负载的 MOT 任务的性能阻止了降级语音的处理,而清晰语音的处理不受影响。随着负载的增加,这些区域对清晰语音的响应下降,这与处理它的能力下降一致。这一结果将认知控制与语音处理分离开来;处理清晰语音所需的认知控制比理解即使是非常轻微退化的 100% 可理解语音所需的认知控制要少得多。

重要性声明即使语音质量下降(例如,由于背景音、电话传输或听力损失),语音通常也能完全听懂。退化如何改变认知需求?在这里,我们使用 fMRI 来证明认知控制在处理轻度退化但完全可理解的语音过程中的新颖和关键作用。我们比较可懂度匹配但假定控制要求不同的语音,将认知控制与语音处理分离。我们还在感知过程中施加参数认知负荷,将依赖于任务的过程与依赖于可用能力的过程分离。我们的研究结果区分了正面和时间对语音感知的贡献,并揭示了处理轻度降级语音的隐藏成本,

更新日期:2022-06-09
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