Reorganization of the Neurobiology of Language After Sentence Overlearning

Abstract

It is assumed that there are a static set of “language regions” in the brain. Yet, language comprehension engages regions well beyond these, and patients regularly produce familiar “formulaic” expressions when language regions are severely damaged. These suggest that the neurobiology of language is not fixed but varies with experiences, like the extent of word sequence learning. We hypothesized that perceiving overlearned sentences is supported by speech production and not putative language regions. Participants underwent 2 sessions of behavioral testing and functional magnetic resonance imaging (fMRI). During the intervening 15 days, they repeated 2 sentences 30 times each, twice a day. In both fMRI sessions, they “passively” listened to those sentences, novel sentences, and produced sentences. Behaviorally, evidence for overlearning included a 2.1-s decrease in reaction times to predict the final word in overlearned sentences. This corresponded to the recruitment of sensorimotor regions involved in sentence production, inactivation of temporal and inferior frontal regions involved in novel sentence listening, and a 45% change in global network organization. Thus, there was a profound whole-brain reorganization following sentence overlearning, out of “language” and into sensorimotor regions. The latter are generally preserved in aphasia and Alzheimer’s disease, perhaps explaining residual abilities with formulaic expressions in both.

When Abstract Becomes Concrete: Naturalistic Encoding of Concepts in the Brain

“…First, in line with previous studies, we predicted that across naturalistic contexts, concrete and abstract concepts are processed in a separable set of brain regions. To test this prediction, we used data from 86 participants who watched one of 10 movies during fMRI (35). The preprocessed data was analyzed using amplitude modulated deconvolution regression (36).…”

“…different word-meanings) and contexts are averaged across, differences in conceptual encoding average out, once thresholded (Wang et al, 2022). Averaging both word-meaning and contextual information leaves only brain regions involved in either a subset of aspects of language processing (like auditory and phonological processing), encoding of linguistic associations, or general regions of high connectivity coordinating more distributed processes (Skipper et al, 2022). Future work should carefully define what aspects of language can be studied with different ways of averaging across word- and context-types.…”

Quantitative MRI reveals differences in striatal myelin in children with DLD

“…The dorsal striatum has been implicated in learning through practice, particularly habit formation (Skipper et al, 2020; Yin & Knowlton, 2006). A number of groups, including us, have hypothesised that the striatum is a brain region where we might expect to see neural differences in children with DLD (Krishnan et al, 2016; Ullman et al, 2020; Ullman & Pierpont, 2005).…”

“…In accordance, a series of behavioural studies has suggested that sequential learning in the linguistic and non-linguistic domains is affected in children with DLD (Hsu & Bishop, 2014; Lum et al, 2014; but see West et al, 2018, 2021). In studies that probe complex sequential production in the vocal domain, the dorsal striatum is implicated (Rauschecker et al, 2008; Simmonds et al, 2014; Skipper et al, 2020). The striatum is structurally and functionally connected to regions associated with language production, with the head of the dorsolateral caudate nucleus receiving inputs from inferior frontal cortex, and the putamen receiving inputs from motor, premotor and supplementary motor cortex (Alexander et al, 1986; Jarbo & Verstynen, 2015; Lima et al, 2016).…”

The entire brain, more or less, is at work: ‘Language regions’ are artefacts of averaging

“…A similar conclusion can be drawn from other linguistic representations. For example, overlearned 'formulaic' language like 'you know' seems to not involve classical 'language regions' at all, explaining why they are often preserved after severe damage, as in global aphasia 34,35 . A similar argument can be made not only for linguistic representations but other linguistic processes.…”