Examining resting state functional connectivity and frequency power analysis in adults who stutter compared to adults who do not stutter.

Introduction: Stuttering is a speech disorder characterized by impaired connections between brain regions involved in speech production. This study aimed to investigate functional connectivity and frequency power during rest in adults who stutter (AWS) compared to fluent adults (AWNS) in the dorsolateral prefrontal cortex (DLPFC), dorsolateral frontal cortex (DLFC), supplementary motor area (SMA), motor speech, angular gyrus (AG), and inferior temporal gyrus (ITG). Materials and methods: Fifteen AWS (3 females, 12 males) and fifteen age- and sex-matched AWNS (3 females, 12 males) participated in this study. All participants were native Persian speakers. Stuttering severity in the AWS group was assessed using the Persian version of the Stuttering Severity Instrument Fourth Edition (SSI-4). Resting-state electroencephalography (EEG) was recorded for 5 min while participants sat comfortably with their eyes open. We analyzed frequency band power across various frequency bands and investigated functional connectivity within the specified speech region. Results: Significant between-group differences were found in band powers including alpha, beta, delta, theta, and gamma, specifically in the premotor, SMA, motor speech, and frontal regions. AWS also showed increased coherence between the right motor speech region compared to controls. We demonstrate that the proposed hierarchical false discovery rate (FDR) method is the most effective for both simulations and experimental data. In the expected regions, this method revealed significant synchrony effects at an acceptable error rate of 5%. Conclusion: The results highlight disrupted functional connectivity in AWS at resting state, particularly in speech-related and associated areas. Given the complex neurological basis of developmental stuttering, robust neural markers are closely linked to this phenomenon. These markers include imbalanced activity within brain regions associated with speech and motor functions, coupled with impaired functional connectivity between these regions. The cortico-basal ganglia-thalamo-cortical system governs the dynamic interplay between cortical regions, with SMA as a key cortical site. It is hypothesized that the aberrant resting state functional connectivity will impact the language planning and motor execution necessary for fluent speech. Examining resting-state metrics as biomarkers could further elucidate the neural underpinnings of stuttering and guide intervention.

Priming Center-Embedded Object and Extraposed Subject Relative Clauses in Persian Language Production: Searching for Persistence of Hierarchical Configuration.

Substantial evidence suggests that priming can co-occur at different syntactic and nonsyntactic levels. In this study, we further explore two loci of priming concerned with hierarchical configuration and thematic information using relative clause (RC) constructions. In a comprehension-to-production task, Persian speakers (42 adults and 42 children) described pictures after hearing extraposed subject or center-embedded object RCs containing the same or different verbs. We ask whether priming the object RC mitigates the computational cost of center-embedding and thus increases the subsequent production of this infrequent structure. We also measured persistence effects associated with the assignment of emphasis to thematic roles, examining whether a particular portrayal of an event is captured and reproduced (e.g., foregrounding the patient). Although this study could not establish any significant priming effects in the production of the center-embedded object RC, we observed that adults used this construction more in the same verbs condition. The overall results instead revealed strong evidence for thematic emphasis persistence, such that patient-emphasis object relatives further elicited functionally equivalent RC constructions. We discuss priming of hierarchical configuration as a candidate locus and explain the activation of functional information from the speaker's perspective.

Overlapping but Language-Specific Mechanisms in Morphosyntactic Processing in Highly Competent L2 Acquired at School Entry: fMRI Evidence From an Alternating Language Switching Task.

Many bilingual individuals acquire their second language when entering primary school; however, very few studies have investigated morphosyntax processing in this population. Combining a whole-brain and region of interest (ROI)-based approach, we studied event-related fMRI during morphosyntactic processing, specifically person-number phi-features, in Turkish (L1) and Persian (L2) by highly proficient bilinguals who learned Persian at school entry. In a design with alternating language switching and pseudorandomized grammaticality conditions, two left-lateralized syntax-specific ROIs and 11 bilateral ROIs involved in executive functions (EF) were analyzed for the intensity of activation relative to a resting baseline. Our findings indicate a strong overlap of neural networks for L1 and L2, suggesting structural similarities of neuroanatomical organization. In all ROIs morphosyntactic processing invoked stronger activation in L1 than in L2. This may be a consequence of symmetrical switch costs in the alternating design used here, where the need for suppressing the non-required language is stronger for the dominant L1 when it is non-required as compared to the non-dominant L2, leading to a stronger rebound for L1 than L2 when the language is required. Both L1 and L2 revealed significant activation in syntax-specific areas in left hemisphere clusters and increased activation in EF-specific areas in right-hemisphere than left-hemisphere clusters, confirming syntax-specific functions of the left hemisphere, whereas the right hemisphere appears to subserve control functions required for switching languages. While previous reports indicate a leftward bias in planum temporale activation during auditory and linguistic processing, the present study shows the activation of the right planum temporale indicating its involvement in auditory attention. More pronounced grammaticality effect in left pars opercularis for L1 and in left pSTG for L2 indicate differences in the processing of morphosyntactic information in these brain regions. Nevertheless, the activation of pars opercularis and pSTG emphasize the centrality of these regions in the processing of person-number phi-features. Taken together, the present results confirm that morphosyntactic processing in bilinguals relates to composite, syntax-sensitive and EF-sensitive mechanisms in which some nodes of the language network are differentially involved.

First Event-Related Potentials Evidence of Auditory Morphosyntactic Processing in a Subject-Object-Verb Nominative-Accusative Language (Farsi).

While most studies on neural signals of online language processing have focused on a few-usually western-subject-verb-object (SVO) languages, corresponding knowledge on subject-object-verb (SOV) languages is scarce. Here we studied Farsi, a language with canonical SOV word order. Because we were interested in the consequences of second-language acquisition, we compared monolingual native Farsi speakers and equally proficient bilinguals who had learned Farsi only after entering primary school. We analyzed event-related potentials (ERPs) to correct and morphosyntactically incorrect sentence-final syllables in a sentence correctness judgment task. Incorrect syllables elicited a late posterior positivity at 500-700 ms after the final syllable, resembling the P600 component, as previously observed for syntactic violations at sentence-middle positions in SVO languages. There was no sign of a left anterior negativity (LAN) preceding the P600. Additionally, we provide evidence for a real-time discrimination of phonological categories associated with morphosyntactic manipulations (between 35 and 135 ms), manifesting the instantaneous neural response to unexpected perturbations. The L2 Farsi speakers were indistinguishable from L1 speakers in terms of performance and neural signals of syntactic violations, indicating that exposure to a second language at school entry may results in native-like performance and neural correlates. In nonnative (but not native) speakers verbal working memory capacity correlated with the late posterior positivity and performance accuracy. Hence, this first ERP study of morphosyntactic violations in a spoken SOV nominative-accusative language demonstrates ERP effects in response to morphosyntactic violations and the involvement of executive functions in non-native speakers in computations of subject-verb agreement.

Processing Conventional Conceptual Metaphors in Persian: A Corpus-Based Psycholinguistic Study.

Research on the psycholinguistic processing of conceptual metaphors has produced contrasting results in recent years. There have also been criticisms that in experimental studies of metaphor processing, linguistic stimuli are mostly intuition-based and not designed objectively based on the original language use data. To address these issues, we studied the processing of conventional metaphoric expressions in Persian language using corpus data. A reading time experiment was designed to test whether conventional metaphoric expressions activated conceptual metaphors. A corpus of 50 million word tokens was used to study the conventional patterns of metaphoric expressions usages and construct experimental items. Fifty five Persian speakers read a set of scenarios containing non-conventional metaphor, conventional metaphor and non-metaphor expressions on computer and the reading times of the following novel target sentence in each condition were recorded by DMDX stimulus presenter program. Comparing mean reading times using one-way ANOVA revealed that reading target sentence after conventional metaphor scenarios had been significantly faster than non-metaphor scenarios, but slower than non-conventional scenarios. The results show that conventionality has a weakening effect on the strength of metaphoric expressions to activate conceptual metaphors.