BCBL, Basque Center on Cognition, Brain and Language, Donostia/San Sebastian, Spain; Ikerbasque, Basque Foundation for Science, Bilbao, Spain.
BCBL, Basque Center on Cognition, Brain and Language, Donostia/San Sebastian, Spain.
Neuropsychologia. 2021 Jun 18;156:107830. doi: 10.1016/j.neuropsychologia.2021.107830. Epub 2021 Mar 24.
Semantic prediction and cortical entrainment to the acoustic landmarks of the speech envelope are two fundamental yet qualitatively different mechanisms that facilitate speech comprehension. However, it is not clear how and to what extent those mechanisms interact with each other. On the one hand, richer semantic context could enhance the perceptual representation of a predictable stimulus, thus improving speech entrainment. On the other hand, pre-activating an upcoming item could inhibit further bottom-up analyses to minimize processing costs, thus weakening speech entrainment. To test these competing hypotheses, we recorded EEG activity from 27 participants while they listened to a 14-min recording of text reading. The passage contained target words presented twice: once in a highly constraining and once in a minimally constraining context. First, we measured event related potentials on target words in the two conditions. In line with previous research, we showed that semantic predictability modulated the N400 amplitude: words in minimally constraining contexts elicited larger negative amplitudes than words in highly constraining contexts between 250 and 450 ms. Second, we evaluated speech entrainment effects by analyzing phase alignment between neural activity and the envelope of target words. Importantly, we found increased speech entrainment for words in minimally constraining compared to highly constraining contexts between 400 and 450 ms. Both effects were located in central electrodes and were significantly correlated. Our results indicate a trade-off between semantic pre-activation and cortical entrainment to speech and support the cost minimization hypothesis.
语义预测和皮质对语音包络的声学分界的同步是促进语音理解的两个基本但性质不同的机制。然而，目前尚不清楚这些机制是如何相互作用的，以及相互作用的程度如何。一方面，更丰富的语义语境可以增强可预测刺激的感知表现，从而提高语音同步。另一方面，预先激活即将到来的项目可以抑制进一步的自下而上的分析，以最小化处理成本，从而削弱语音同步。为了检验这些相互竞争的假设，我们在 27 名参与者听 14 分钟的文本阅读录音时记录了他们的 EEG 活动。这段文字包含了两次出现的目标词：一次出现在高度约束的语境中，一次出现在最小约束的语境中。首先，我们在两种条件下测量了目标词的事件相关电位。与先前的研究一致，我们表明语义可预测性调制了 N400 幅度：在最小约束语境中出现的词比在高度约束语境中出现的词在 250 到 450 毫秒之间产生更大的负幅度。其次，我们通过分析目标词的神经活动与包络之间的相位对齐来评估语音同步效应。重要的是，我们发现，在最小约束语境中，与在高度约束语境中相比，目标词的语音同步效应在 400 到 450 毫秒之间有所增加。这两种效应都位于中央电极上，且显著相关。我们的研究结果表明，语义预激活和皮质对语音的同步之间存在权衡关系，并支持成本最小化假说。
