Does Semantic Context Benefit Speech Understanding through "Top-Down" Processes? Evidence from Time-resolved Sparse fMRI
Does Semantic Context Benefit Speech Understanding through "Top-Down" Processes? Evidence from Time-resolved Sparse fMRI
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DOI：
10.1162/jocn_a_00084
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发表时间：
2011-12-01
影响因子：
3.2
通讯作者：
Johnsrude, Ingrid S.
中科院分区：
文献类型：
--
作者：
Davis, Matthew H.;Ford, Michael A.;Johnsrude, Ingrid S.
当语音降级时，对于语义连贯的句子（例如，她的新裙子是牛仔布做的）而不是异常的句子（例如，她那漂亮斜坡是用胡萝卜做的）。这种增加的可理解性通常被描述为“自上而下”的过程，反映了一个假设，即更高级别（语义）的神经过程支持较低级别（感知）的机制。我们使用时间分辨稀疏功能磁共振成像测试自上而下的神经机制，测量活动，而参与者听到连贯和异常的句子在语音包络/频谱噪声在不同的信噪比（SNR）。BOLD反应的时间更清晰的语音提供了层次组织的证据，与更远的颞叶和额叶区域相比，在后上级颞回的听觉周围区域的反应更早。尽管句子内容x SNR在上级颞回中相互作用，但前额叶区域在听觉/感知区域之后响应。虽然我们不能排除自上而下的影响，但这种模式更适合于纯粹的前馈或自下而上的解释，在这种解释中，较低水平的知觉处理结果被传递到下额叶区域。行为和神经的证据表明，句子内容的影响，降低语音的看法并不一定意味着“自上而下”的神经过程。
When speech is degraded, word report is higher for semantically coherent sentences (e.g., her new skirt was made of denim) than for anomalous sentences (e.g., her good slope was done in carrot). Such increased intelligibility is often described as resulting from "top-down" processes, reflecting an assumption that higher-level (semantic) neural processes support lower-level (perceptual) mechanisms. We used time-resolved sparse fMRI to test for top-down neural mechanisms, measuring activity while participants heard coherent and anomalous sentences presented in speech envelope/spectrum noise at varying signal-to-noise ratios (SNR). The timing of BOLD responses to more intelligible speech provides evidence of hierarchical organization, with earlier responses in peri-auditory regions of the posterior superior temporal gyrus than in more distant temporal and frontal regions. Despite Sentence content x SNR interactions in the superior temporal gyrus, prefrontal regions respond after auditory/perceptual regions. Although we cannot rule out top-down effects, this pattern is more compatible with a purely feedforward or bottom-up account, in which the results of lower-level perceptual processing are passed to inferior frontal regions. Behavioral and neural evidence that sentence content influences perception of degraded speech does not necessarily imply "top-down" neural processes.