Hijacking limitations of working memory load to test for composition in language.

Although language depends on storage and composition, just what is stored or (de)composed remains unclear. We leveraged working memory load limitations to test for composition, hypothesizing that decomposed forms should particularly tax working memory. We focused on a well-studied paradigm, English inflectional morphology. We predicted that (compositional) regulars should be harder to maintain in working memory than (non-compositional) irregulars, using a 3-back production task. Frequency, phonology, orthography, and other potentially confounding factors were controlled for. Compared to irregulars, regulars and their accompanying -s/-ing-affixed filler items yielded more errors. Underscoring the decomposition of only regulars, regulars yielded more bare-stem (e.g., walk) and stem affixation errors (walks/walking) than irregulars, whereas irregulars yielded more past-tense-form affixation errors (broughts/tolded). In line with previous evidence that regulars can be stored under certain conditions, the regular-irregular difference held specifically for phonologically consistent (not inconsistent) regulars, in particular for both low and high frequency consistent regulars in males, but only for low frequency consistent regulars in females. Sensitivity analyses suggested the findings were robust. The study further elucidates the computation of inflected forms, and introduces a simple diagnostic for linguistic composition.

Characterization of speech and language phenotype in the 8p23.1 syndrome.

The 8p23.1 duplication syndrome is a rare genetic condition with an estimated prevalence rate of 1 out of 58,000. Although the syndrome was associated with speech and language delays, a comprehensive assessment of speech and language functions has not been undertaken in this population. To address this issue, the present study reports rigorous speech and language, in addition to oral-facial and developmental, assessment of a 50-month-old Turkish-speaking boy who was diagnosed with the 8p23.1 duplication syndrome. Standardized tests of development, articulation and phonology, receptive and expressive language and a language sample analysis were administered to characterize speech and language skills in the patient. The language sample was obtained in an ecologically valid, free play and conversation context. The language sample was then analyzed and compared to a database of age-matched typically-developing children (n = 33) in terms of intelligibility, morphosyntax, semantics/vocabulary, discourse, verbal facility and percentage of errors at word and utterance levels. The results revealed mild to severe problems in articulation and phonology, receptive and expressive language skills, and morphosyntax (mean length of utterance in morphemes). Future research with larger sample sizes and employing detailed speech and language assessment is needed to delineate the speech and language profile in individuals with the 8p23.1 duplication syndrome, which will guide targeted speech and language interventions.

Contributions of the left and right thalami to language: A meta-analytic approach.

BACKGROUND: Despite a pervasive cortico-centric view in cognitive neuroscience, subcortical structures including the thalamus have been shown to be increasingly involved in higher cognitive functions. Previous structural and functional imaging studies demonstrated cortico-thalamo-cortical loops which may support various cognitive functions including language. However, large-scale functional connectivity of the thalamus during language tasks has not been examined before. METHODS: The present study employed meta-analytic connectivity modeling to identify language-related coactivation patterns of the left and right thalami. The left and right thalami were used as regions of interest to search the BrainMap functional database for neuroimaging experiments with healthy participants reporting language-related activations in each region of interest. Activation likelihood estimation analyses were then carried out on the foci extracted from the identified studies to estimate functional convergence for each thalamus. A functional decoding analysis based on the same database was conducted to characterize thalamic contributions to different language functions. RESULTS: The results revealed bilateral frontotemporal and bilateral subcortical (basal ganglia) coactivation patterns for both the left and right thalami, and also right cerebellar coactivations for the left thalamus, during language processing. In light of previous empirical studies and theoretical frameworks, the present connectivity and functional decoding findings suggest that cortico-subcortical-cerebellar-cortical loops modulate and fine-tune information transfer within the bilateral frontotemporal cortices during language processing, especially during production and semantic operations, but also other language (e.g., syntax, phonology) and cognitive operations (e.g., attention, cognitive control). CONCLUSION: The current findings show that the language-relevant network extends beyond the classical left perisylvian cortices and spans bilateral cortical, bilateral subcortical (bilateral thalamus, bilateral basal ganglia) and right cerebellar regions.

Domain-general and domain-specific functional networks of Broca's area underlying language processing.

INTRODUCTION: Despite abundant research on the role of Broca's area in language processing, there is still no consensus on language specificity of this region and its connectivity network. METHODS: The present study employed the meta-analytic connectivity modeling procedure to identify and compare domain-specific (language-specific) and domain-general (shared between language and other domains) functional connectivity patterns of three subdivisions within the broadly defined Broca's area: pars opercularis (IFGop), pars triangularis (IFGtri), and pars orbitalis (IFGorb) of the left inferior frontal gyrus. RESULTS: The findings revealed a left-lateralized frontotemporal network for all regions of interest underlying domain-specific linguistic functions. The domain-general network, however, spanned frontoparietal regions that overlap with the multiple-demand network and subcortical regions spanning the thalamus and the basal ganglia. CONCLUSIONS: The findings suggest that language specificity of Broca's area emerges within a left-lateralized frontotemporal network, and that domain-general resources are garnered from frontoparietal and subcortical networks when required by task demands.

Meta-analytic connectivity modeling of the left and right inferior frontal gyri.

BACKGROUND: Neurocognitive models of language processing highlight the role of the left inferior frontal gyrus (IFG) in the functional network underlying language. Furthermore, neuroscience research has shown that IFG is not a uniform region anatomically, cytoarchitectonically or functionally. However, no previous study explored the language-related functional connectivity patterns of IFG subdivisions using a meta-analytic connectivity modeling (MACM) approach. PURPOSE: The present MACM study aimed to identify language-related coactivation patterns of the left and right IFG subdivisions. METHOD: Six regions of interest (ROIs) were defined using a probabilistic brain atlas corresponding to pars opercularis, pars triangularis and pars orbitalis of IFG in both hemispheres. The ROIs were used to search the BrainMap functional database to identify neuroimaging experiments with healthy, right-handed participants reporting language-related activations in each ROI. Activation likelihood estimation analyses were then performed on the foci extracted from the identified studies to compute functional convergence for each ROI, which was also contrasted with the other ROIs within the same hemisphere. RESULTS: A primarily left-lateralized functional network was revealed for the left and right IFG subdivisions. The left-hemispheric ROIs exhibited more robust coactivation than the right-hemispheric ROIs. Particularly, the left pars opercularis was associated with the most extensive coactivation pattern involving bilateral frontal, bilateral parietal, left temporal, left subcortical, and right cerebellar regions, while the left pars triangularis and orbitalis revealed a predominantly left-lateralized involvement of frontotemporal regions. CONCLUSION: The findings align with the neurocognitive models of language processing that propose a division of labor among the left IFG subdivisions and their respective functional networks. Also, the opercular part of left IFG stands out as a major hub in the language network with connections to diverse cortical, subcortical and cerebellar structures.

Neural correlates of morphological processing: An activation likelihood estimation meta-analysis.

BACKGROUND: Morphemes are the smallest building blocks of language that convey meaning or function. A controversial issue in psycho- and neurolinguistics is whether morphologically complex words consisting of multiple morphemes are processed in a combinatorial manner and, if so, which brain regions underlie this process. Relatively less is known about the neural underpinnings of morphological processing compared to other aspects of grammatical competence such as syntax. PURPOSE: The present study aimed to shed light on the neural correlates of morphological processing by examining functional convergence for inflectional morphology reported in previous neuroimaging studies. METHOD: A systematic literature search was performed on PubMed with search terms related to morphological complexity and neuroimaging. 16 studies (279 subjects) comparing regular inflection with stems or irregular inflection met the inclusion and exclusion criteria and were subjected to a series of activation likelihood estimation meta-analyses. RESULTS: Significant functional convergence was found in several mainly left frontal regions for processing inflectional morphology. Specifically, the left inferior frontal gyrus (LIFG) was found to be consistently involved in morphological complexity. Diagnostic analyses revealed that involvement of posterior LIFG was robust against potential publication bias and over-influence of individual studies. Furthermore, LIFG involvement was maintained in meta-analyses of subsets of experiments that matched phonological complexity between conditions, although diagnostic analyses suggested that this conclusion may be premature. CONCLUSION: The findings provide evidence for combinatorial processing of morphologically complex words and inform psycholinguistic accounts of complex word processing. Furthermore, they highlight the role of LIFG in processing inflectional morphology, in addition to syntactic processing as has been emphasized in previous research. In particular, posterior LIFG seems to underlie grammatical functions encompassing inflectional morphology and syntax.

Is There a Processing Preference for Object Relative Clauses in Chinese? Evidence From ERPs.

A consistent finding across head-initial languages, such as English, is that subject relative clauses (SRCs) are easier to comprehend than object relative clauses (ORCs). However, several studies in Mandarin Chinese, a head-final language, revealed the opposite pattern, which might be modulated by working memory (WM) as suggested by recent results from self-paced reading performance. In the present study, event-related potentials (ERPs) were recorded when participants with high and low WM spans (measured by forward digit span and operation span tests) read Chinese ORCs and SRCs. The results revealed an N400-P600 complex elicited by ORCs on the relativizer, whose magnitude was modulated by the WM span. On the other hand, a P600 effect was elicited by SRCs on the head noun, whose magnitude was not affected by the WM span. These findings paint a complex picture of relative clause processing in Chinese such that opposing factors involving structural ambiguities and integration of filler-gap dependencies influence processing dynamics in Chinese relative clauses.

Neural correlates of processing sentences and compound words in Chinese.

Sentence reading involves multiple linguistic operations including processing of lexical and compositional semantics, and determining structural and grammatical relationships among words. Previous studies on Indo-European languages have associated left anterior temporal lobe (aTL) and left interior frontal gyrus (IFG) with reading sentences compared to reading unstructured word lists. To examine whether these brain regions are also involved in reading a typologically distinct language with limited morphosyntax and lack of agreement between sentential arguments, an FMRI study was conducted to compare passive reading of Chinese sentences, unstructured word lists and disconnected character lists that are created by only changing the order of an identical set of characters. Similar to previous findings from other languages, stronger activation was found in mainly left-lateralized anterior temporal regions (including aTL) for reading sentences compared to unstructured word and character lists. On the other hand, stronger activation was identified in left posterior temporal sulcus for reading unstructured words compared to unstructured characters. Furthermore, reading unstructured word lists compared to sentences evoked stronger activation in left IFG and left inferior parietal lobule. Consistent with the literature on Indo-European languages, the present results suggest that left anterior temporal regions subserve sentence-level integration, while left IFG supports restoration of sentence structure. In addition, left posterior temporal sulcus is associated with morphological compounding. Taken together, reading Chinese sentences engages a common network as reading other languages, with particular reliance on integration of semantic constituents.