Wave arts power suite 5.473/31/2023 ![]() ![]() Prior knowledge plays a decisive role in word recognition. “analysis-by-synthesis” Halle and Stevens 1959 Poeppel et al. On this view, resolved speech content constitutes the brain’s “best guess” about the causes of its sensory input, given an internal model of the way sensations are generated (cf. from lexical, speaker, or world-knowledge) and “bottom-up” sensory evidence (see Friston and Kiebel 2009 Heilbron and Chait 2018). Contemporary predictive coding models of speech processing formalize this notion in terms of (hierarchical) Bayesian inference, whereby perceptual experience reflects the integration of “top-down” prior expectations (derived, e.g. ![]() Miller and Isard 1963 Tulving and Gold 1963). Prediction has long been accorded an important role in language comprehension (e.g. However, the neurocomputational mechanisms supporting such processes remain poorly understood. There is growing consensus that the brain meets these demands by predicting sensory input on the basis of prior knowledge ( Kuperberg and Jaeger 2016 Bornkessel-Schlesewsky and Schlesewsky 2019 Brodbeck and Simon 2020). Such processing must occur quickly enough to keep abreast of the unfolding speech stream ( Christiansen and Chater 2016), while remaining robust to signal variation and degradation ( Mattys et al. Fluent speech recognition requires the parsing of a continuously changing acoustic signal into a series of discrete units, and the mapping of these units onto abstract representations spanning multiple scales ( Halle and Stevens 1962 Hickok and Poeppel 2007). The ability to understand spoken language is a remarkable feat of human cognition. Together, these findings reveal distinctive profiles of neurophysiological activity that differentiate the content-specific processes associated with degraded speech comprehension from the context-specific processes invoked under adverse listening conditions. Moreover, delta-band power, alpha-band power, and pupil diameter were all increased following the provision of any written sentence information, irrespective of content. Spectral analysis further revealed that pop-out was accompanied by a reduction in theta-band power, consistent with predictive coding accounts of acoustic filling-in and incremental sentence processing. Pop-out was associated with improved reconstruction of the acoustic stimulus envelope from low-frequency EEG activity, implying that improvements in perceptual clarity were mediated via top-down signals that enhanced the quality of cortical speech representations. Pop-out was reliably elicited following visual presentation of the corresponding written sentence, but not following incongruent or neutral text. We recorded electroencephalography (EEG) and pupillometry from 21 adults while they rated the clarity of noise-vocoded and sine-wave synthesized sentences. the dramatic improvement of speech intelligibility after receiving information about speech content) to investigate the neurophysiological effects of prior expectations on degraded speech comprehension. ![]() Here, we exploit the perceptual “pop-out” phenomenon (i.e. Online speech processing imposes significant computational demands on the listening brain, the underlying mechanisms of which remain poorly understood. ![]()
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