Temporal lobe perceptual predictions for speech are instantiated in motor cortex and reconciled by inferior frontal cortex

Humans use predictions to improve speech perception, especially in noisy environments. Here we use 7-T functional MRI (fMRI) to decode brain representations of written phonological predictions and degraded speech signals in healthy humans and people with selective frontal neurodegeneration (non-fluent variant pri-mary progressive aphasia [nfvPPA]). Multivariate analyses of item-specific patterns of neural activation indi-cate dissimilar representations of verified and violated predictions in left inferior frontal gyrus, suggestive of processing by distinct neural populations. In contrast, precentral gyrus represents a combination of phono-logical information and weighted prediction error. In the presence of intact temporal cortex, frontal neurode-generation results in inflexible predictions. This manifests neurally as a failure to suppress incorrect predic-tions in anterior superior temporal gyrus and reduced stability of phonological representations in precentral gyrus. We propose a tripartite speech perception network in which inferior frontal gyrus supports prediction reconciliation in echoic memory, and precentral gyrus invokes a motor model to instantiate and refine perceptual predictions for speech.

Automated summary

Humans use predictions to improve speech perception, especially in noisy environments. Brain representations of written phonological predictions and degraded speech signals were decoded using 7-T functional MRI in both healthy humans and people with frontal neurodegeneration. Different neural populations process verified and violated predictions in the inferior frontal gyrus, while the precentral gyrus combines phonological information with prediction error. Frontal neurodegeneration leads to inflexible predictions and neural manifestations include failure to suppress incorrect predictions in the anterior superior temporal gyrus and reduced stability of phonological representations in the precentral gyrus. A tripartite speech perception network is proposed, with the inferior frontal gyrus supporting prediction reconciliation and the precentral gyrus using a motor model to refine perceptual predictions for speech.