Neurobiology of Language

A common practice in the cognitive neurosciences is to investigate population-typical phenomena, treating individuals as equal except for a few outliers that are usually discarded from analyses or that disappear on group-level patterns. Only a few studies to date have captured the heterogeneity of language processing across individuals as so-called “individual differences;” fewer have explicitly researched language aptitude, which designates an individual’s ability for acquiring foreign languages. Existing studies show that, relative to average learners, very gifted language learners display different task-related patterns of functional activation and connectivity during linguistic tasks, and structural differences in white and grey matter morphology, and in white matter connectivity. Despite growing interest in language aptitude, there is no recent comprehensive review, nor a theoretical model to date that includes the neural level. To fill this gap, we review neuroscientific resea...

This paper explores the content of the somniloquies of Dion McGregor, the most extensive sleep talker ever recorded, and compares these with dream content from normative male dreams on the Hall and van de Castle Content Scales (1966) and Hobson (et al., 1987) Bizarreness Scales. On the Hall and van de Castle Scales, the somniloquies contained significantly more female characters relative to males than for the norms, more familiar characters and friends, but fewer family members. The dreamer-as-character was much likelier to be either a befriender or an aggressor than in the normative dreams but much less likely to engage in physical aggression specifically.  There was less aggression, friendliness, or sex per character in McGregor’s narratives, as well as less of all three of these types of interaction total than for the norms, but much more self negativity.  There was a lower percentage of negative emotions, good fortune, and success, but the somniloquies were similar to the norms in their levels of misfortune and failure.    On the Hobson Bizarreness Scales, the McGregor somniloquies were not differentiated from dreams on 3 of 6 scales—having similar levels of discontinuity of plot, characters, object, or actions but had slightly fewer incongruities of plot, and many fewer instances of incongruity or  uncertainly of thought. These findings are discussed in terms of presumed brain activation differences—more frontal activation--and also in terms of McGregor’s (1964) personal idiosyncrasies.

Activity in frontocentral motor regions is routinely reported when individuals process action words and is often interpreted as the implicit simulation of the word content. We hypothesized that these neural responses are not invariant components of action word processing but are modulated by the context in which they are evoked. Using fMRI, we assessed the relative weight of stimulus features (i.e., the intrinsic semantics of words) and contextual factors, in eliciting word-related sensorimotor activity. Participants silently read action-related and state verbs after performing a mental rotation task engaging either a motor strategy (i.e., referring visual stimuli to their own bodily movements) or a visuospatial strategy. The mental rotation tasks were used to induce, respectively, a motor and a nonmotor "cognitive context" into the following silent reading. Irrespective of the verb category, reading in the motor context, compared with reading in the nonmotor context, increased the activity in the left primary motor cortex, the bilateral premotor cortex, and the right somatosensory cortex. Thus, the cognitive context induced by the preceding motor strategy-based mental rotation modulated word-related sensorimotor responses, possibly reflecting the strategy of referring a word meaning to one's own bodily activity. This pattern, common to action and state verbs, suggests that the context in which words are encountered prevails over the intrinsic semantics of the stimuli in mediating the recruitment of sensorimotor regions.

This study present a collection of examples of verbatim language in dreams, with analyses of how this is altered relative to waking language. Grammar is well-preserved in these dreams while meaningfulness is distorted relative to waking criteria. Novel nouns receive special emphasis as do extra-vocal cues such as voice tone. Dreams with verbatim language tend to be unusually long, vivid, and emotionally salient, though this may be a byproduct differential dream recall affecting both.  The present findings will be compared to past research data on language in dreams, and discussed in relation to what's known about brain areas involved in dreaming and areas involved in different linguistic processes.

Developmental stuttering is a childhood onset neurodevelopmental disorder with an unclear etiology. Subtle changes in brain structure and function are present in both children and adults who stutter. It is a highly heritable disorder, and up to 12-20% of stuttering cases may carry a mutation in one of four genes involved in mannose-6-phosphate mediated protein intracellular trafficking. To better understand the relationship between genetic factors and brain structural changes, we used gene expression data from the Allen Institute for Brain Science (AIBS) and voxel-based morphometry (VBM) to investigate the spatial correspondence between gene expression patterns and differences in gray matter volume (GMV) between children with persistent stuttering (n=26, 87 scans) and their fluent peers (n=44, 139 scans). We found that expression patterns of two stuttering-related genes (GNPTG and NAGPA) in the brain exhibit a strong positive spatial correlation with the magnitude of GMV differences...

Speech comprehension requires rapid online processing of a continuous acoustic signal to extract structure and meaning. Previous studies on sentence comprehension have found neural correlates of the predictability of a word given its context, as well as of the precision of such a prediction. However, they have focused on single sentences and on particular words in those sentences. Moreover, they compared neural responses to words with low and high predictability, as well as with low and high precision. However, in speech comprehension, a listener hears many successive words whose predictability and precision vary over a large range. Here, we show that cortical activity in different frequency bands tracks word surprisal in continuous natural speech and that this tracking is modulated by precision. We obtain these results through quantifying surprisal and precision from naturalistic speech using a deep neural network and through relating these speech features to EEG responses of human volunteers acquired during auditory story comprehension. We find significant cortical tracking of surprisal at low frequencies, including the delta band as well as in the higher frequency beta and gamma bands, and observe that the tracking is modulated by the precision. Our results pave the way to further investigate the neurobiology of natural speech comprehension.

Language comprehension involves the simultaneous processing of information at the pho-nological, syntactic, and lexical level. We track these three distinct streams of information in the brain by using stochastic measures derived from computational language models to detect neural correlates of phoneme, part-of-speech, and word processing in an fMRI experiment. Probabilistic language models have proven to be useful tools for studying how language is processed as a sequence of symbols unfolding in time. Conditional probabilities between sequences of words are at the basis of probabilistic measures such as surprisal and perplexity which have been successfully used as predictors of several behavioural and neural correlates of sentence processing. Here we computed perplexity from sequences of words and their parts of speech, and their phonemic transcriptions. Brain activity time-locked to each word is regressed on the three model-derived measures. We observe that the brain keeps track of the statistical structure of lexical, syntactic and phonological information in distinct areas.

During discourse comprehension, information from prior processing is integrated and appears to be immediately accessible. This was remarkably demonstrated by an N400 for “salted” and not “in love” in response to “The peanut was salted/in love.” Discourse overrule was induced by prior discourse featuring the peanut as an animate agent. Immediate discourse overrule requires a model that integrates information at two timescales. One is over the lifetime and includes event knowledge and word semantics. The second is over the discourse in an event context. We propose a model where both are accounted for by temporal-to-spatial integration of experience into distributed spatial representations, providing immediate access to experience accumulated over different timescales. For lexical semantics, this is modeled by a word embedding system trained by sequential exposure to the entire Wikipedia corpus. For discourse, this is modeled by a recurrent reservoir network trained to generate a disco...

Autism spectrum disorder (ASD) is associated with marked heterogeneity with respect to the development of executive function abilities. The ‘bilingual advantage’ refers to the observation that individuals who speak two languages perform better on executive function tasks than monolinguals under some circumstances. There is not yet consensus, however, as to whether this advantage can be reliably demonstrated, nor is there consensus regarding under which conditions it emerges. Bilingual and monolingual children with ASD have comparable developmental outcomes, particularly in the areas of core ASD symptoms, cognitive function, and language. Still, despite the potential advantages that bilingualism may confer, clinicians commonly advise against providing a bilingual environment for children with ASD. The purpose of the present review is to provide an up-to-date assessment of the limited literature on bilingualism in children with ASD in order to inform evidence-based practice. Studies s...

Stuttering is a neurodevelopmental disorder characterized by impaired execution of articulatory movements needed for fluent speech production. Existing theoretical models propose that these deficits reflect a malfunction in the cortico-basal-ganglia-thalamocortical (cortico-BG) loop that is responsible for selecting and initiating speech motor programs. However, the cortico-BG loop has also been hypothesized to play a role in speech motor learning. To distinguish motor execution impairments from motor learning impairments in stuttering, the authors examined the behavioral and neural correlates of learning to produce novel phoneme sequences in adults who stutter (AWS) and neurotypical controls. Participants intensively practiced producing pseudowords containing non-native consonant clusters over two days. Results showed that, behaviorally, both AWS and controls produced the words with increased speed and accuracy following motor practice, and the rate of improvement was comparable fo...

The topological organization of the brain, governed by the capacity of brain regions to synchronize their activity, allows for cost-effective performance during everyday cognitive activity. Functional connectivity is an fMRI method deemed task-specific and demanddependent. While the brain undergoes significant changes during healthy aging, conceptual knowledge and word production accuracy are generally preserved. The exploration of taskinduced functional connectivity (FC) patterns during active picture naming may thus provide additional information about healthy functional cerebral mechanisms that are specifically adapted to the cognitive activity at hand. The goal of this study is to assess and describe age-related differences in functional connectivity during an overt picture-naming task, as well as to compare age-related differences under complex task demand, defined by lexical frequency. Results suggest both age- and task-specific mechanisms. In the context of preserved behavior...

Developmental stuttering is a childhood onset neurodevelopmental disorder with an unclear etiology. Subtle changes in brain structure and function are present in both children and adults who stutter. It is a highly heritable disorder, and up to 12-20% of stuttering cases may carry a mutation in one of four genes involved in mannose-6-phosphate mediated protein intracellular trafficking. To better understand the relationship between genetic factors and brain structural changes, we used gene expression data from the Allen Institute for Brain Science (AIBS) and voxel-based morphometry (VBM) to investigate the spatial correspondence between gene expression patterns and differences in gray matter volume (GMV) between children with persistent stuttering (n=26, 87 scans) and their fluent peers (n=44, 139 scans). We found that expression patterns of two stuttering-related genes (GNPTG and NAGPA) in the brain exhibit a strong positive spatial correlation with the magnitude of GMV differences...