Rimmele Johanna M, Zion Golumbic Elana, Schröger Erich, Poeppel David
Department of Psychology and Center for Neural Science, New York University, New York, NY, USA; Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Gonda Center for Brain Research, Bar Ilan University, Israel; Department of Psychiatry, Columbia University, New York, NY, USA.
Cortex. 2015 Jul;68:144-54. doi: 10.1016/j.cortex.2014.12.014. Epub 2015 Jan 7.
Attending to one speaker in multi-speaker situations is challenging. One neural mechanism proposed to underlie the ability to attend to a particular speaker is phase-locking of low-frequency activity in auditory cortex to speech's temporal envelope ("speech-tracking"), which is more precise for attended speech. However, it is not known what brings about this attentional effect, and specifically if it reflects enhanced processing of the fine structure of attended speech. To investigate this question we compared attentional effects on speech-tracking of natural versus vocoded speech which preserves the temporal envelope but removes the fine structure of speech. Pairs of natural and vocoded speech stimuli were presented concurrently and participants attended to one stimulus and performed a detection task while ignoring the other stimulus. We recorded magnetoencephalography (MEG) and compared attentional effects on the speech-tracking response in auditory cortex. Speech-tracking of natural, but not vocoded, speech was enhanced by attention, whereas neural tracking of ignored speech was similar for natural and vocoded speech. These findings suggest that the more precise speech-tracking of attended natural speech is related to processing its fine structure, possibly reflecting the application of higher-order linguistic processes. In contrast, when speech is unattended its fine structure is not processed to the same degree and thus elicits less precise speech-tracking more similar to vocoded speech.
在多说话者的情境中专注于一个说话者具有挑战性。一种被认为是支持专注于特定说话者能力的神经机制是听觉皮层中低频活动与语音的时间包络（“语音跟踪”）的锁相，对于被关注的语音来说这种锁相更为精确。然而，尚不清楚是什么导致了这种注意力效应，特别是它是否反映了对被关注语音精细结构的增强处理。为了研究这个问题，我们比较了注意力对自然语音和语码转换语音（保留时间包络但去除语音精细结构）语音跟踪的影响。同时呈现自然语音和语码转换语音刺激对，参与者专注于一个刺激并执行检测任务，同时忽略另一个刺激。我们记录了脑磁图（MEG）并比较了注意力对听觉皮层中语音跟踪反应的影响。注意力增强了自然语音而非语码转换语音的语音跟踪，而对于被忽略的语音，自然语音和语码转换语音的神经跟踪相似。这些发现表明，对被关注自然语音更精确的语音跟踪与处理其精细结构有关，可能反映了高阶语言过程的应用。相比之下，当语音未被关注时，其精细结构没有得到同等程度的处理，因此引发的语音跟踪不如语码转换语音精确。
