Brain Research Unit, Low Temperature Laboratory, Aalto University, FI-00076 Aalto, Finland.
Cereb Cortex. 2012 Oct;22(10):2305-12. doi: 10.1093/cercor/bhr307. Epub 2011 Nov 3.
Word processing is often probed with experiments where a target word is primed by preceding semantically or phonologically related words. Behaviorally, priming results in faster reaction times, interpreted as increased efficiency of cognitive processing. At the neural level, priming reduces the level of neural activation, but the actual neural mechanisms that could account for the increased efficiency have remained unclear. We examined whether enhanced information transfer among functionally relevant brain areas could provide such a mechanism. Neural activity was tracked with magnetoencephalography while subjects read lists of semantically or phonologically related words. Increased priming resulted in reduced cortical activation. In contrast, coherence between brain regions was simultaneously enhanced. Furthermore, while the reduced level of activation was detected in the same area and time window (superior temporal cortex [STC] at 250-650 ms) for both phonological and semantic priming, the spatiospectral connectivity patterns appeared distinct for the 2 processes. Causal interactions further indicated a driving role for the left STC in phonological processing. Our results highlight coherence as a neural mechanism of priming and dissociate semantic and phonological processing via their distinct connectivity profiles.
文字处理通常通过实验进行探测，其中目标词由语义或语音上相关的词先行刺激。从行为上看，启动会导致反应时间加快，这被解释为认知加工效率的提高。在神经水平上，启动会降低神经激活水平，但仍不清楚是什么样的神经机制可以解释这种效率的提高。我们研究了功能相关的脑区之间增强的信息传递是否可以提供这样的机制。在被试阅读语义或语音相关词的列表时，我们利用脑磁图追踪神经活动。增强的启动导致皮质激活减少。相比之下，大脑区域之间的相干性同时增强。此外，虽然在相同的区域和时间窗口（语音和语义启动时的颞上回[STC]在 250-650ms）检测到了相同的激活水平降低，但这 2 个过程的频谱连通模式明显不同。因果相互作用进一步表明，左 STC 在语音处理中起驱动作用。我们的研究结果强调了相干性作为启动的神经机制，并通过其独特的连通性模式区分了语义和语音处理。
