EEG shows brain can simultaneously encode two speech streams

脑电图显示大脑可同时编码两条语音流

Successful speech communication in multi-talker scenarios requires a skillful combination of sustained attention and rapid attention switching. While the neurophysiology literature offers detailed insights into the neural underpinnings of sustained attention, there remains considerable uncertainty on how attention switching takes place. 在多说话人场景中，成功的语音交流需要持续注意力与快速注意力切换的巧妙结合。尽管神经生理学文献对持续注意力的神经基础提供了详尽的见解，但关于注意力切换是如何发生的，目前仍存在相当大的不确定性。

In this study, using EEG recordings from normal-hearing adults in an immersive multi-talker environment, we measured the neural encoding of two competing speech streams amid background babble. Participants were cued to switch attention between streams every 15–30 s. Neural tracking was assessed via Temporal Response Functions (TRF), confirming reliable decoding of attentional focus. 在本研究中，我们利用沉浸式多说话人环境中听力正常成年人的脑电图（EEG）记录，测量了背景嘈杂声中两条竞争语音流的神经编码。参与者被提示每 15-30 秒在不同语音流之间切换注意力。通过时间响应函数（TRF）评估神经追踪，证实了对注意力焦点的可靠解码。

Our results indicate asymmetric disengagement and engagement processes during attention switches, where the neural tracking of the new target stream emerges before disengaging from the previous target, revealing a transient simultaneous encoding of two speech streams. That transition was closely mirrored by a reduction in EEG alpha power, informing on the cognitive effort during different phases of the attention switch. 我们的研究结果表明，在注意力切换过程中存在不对称的脱离与参与过程：即在脱离前一个目标之前，对新目标语音流的神经追踪就已经出现，这揭示了大脑对两条语音流的瞬时同步编码。这种转换与脑电图 Alpha 波功率的降低密切相关，反映了注意力切换不同阶段的认知努力程度。

We then isolated cortical activity reflecting lexical prediction mechanisms to determine how lexical context is updated after an attention switch, comparing four context-accumulation strategies that were constructed using Large Language Models. Our findings elucidate both the temporal and contextual mechanisms underlying auditory attention shifts, pointing to the possibility that listeners carry out a reset in lexical context after switching attention. 随后，我们分离出反映词汇预测机制的皮层活动，以确定注意力切换后词汇上下文是如何更新的，并比较了使用大语言模型构建的四种上下文积累策略。我们的发现阐明了听觉注意力转移背后的时间与上下文机制，指出听者在切换注意力后可能会对词汇上下文进行重置。

By focusing on dynamic attentional reallocation, this study offers insights into the brain’s capacity for flexible speech processing in complex listening environments. 通过聚焦于动态的注意力重分配，本研究为大脑在复杂听觉环境中进行灵活语音处理的能力提供了见解。

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Citation: Carta S, Aličković E, Zaar J, López Valdés A, Di Liberto GM (2026) Competing speech streams are simultaneously represented in the human cortex during attention switching. PLoS Biol 24(7): e3003876. https://doi.org/10.1371/journal.pbio.3003876

引用信息： Carta S, Aličković E, Zaar J, López Valdés A, Di Liberto GM (2026) Competing speech streams are simultaneously represented in the human cortex during attention switching. PLoS Biol 24(7): e3003876. https://doi.org/10.1371/journal.pbio.3003876