Journal of Neurolinguistics最新文献

Background

Speech in persons with Parkinson's disease (PD) is characterized by impaired prosody (e.g., monotone, abnormal rate, reduced loudness). Most studies on prosodic abnormalities in PD have been obtained from individuals who speak non-tone languages, where prosodic contrasts do not systematically contribute to lexical meanings. In a tone language such as Mandarin, pitch not only carries affective information but also serves to distinguish lexical meanings. It is not known how well persons with PD, who speak a tone language, convey contrastive stress (specific intonational cues signaling topic and theme) for discourse purposes in production, or how well they perceive these contrasts.

Method

Experiment 1 investigated production of contrastive stress by persons with PD who speak Mandarin using two different speech tasks, Elicitation and Repetition. PD participants and healthy controls (HC) produced short sentences with focus in different positions during the two task conditions. As an indirect measurement of the quality of the participants’ production of contrastive stress, healthy listeners served as raters to identify focus positions in the sentences and provide goodness ratings to each produced contrastive stress. Experiment 2 examined perceptual ability, measuring PD participants' identification through listening of contrastive stress on utterances produced by a healthy speaker.

Results

For the Production Study (Experiment 1), the results revealed significantly poorer performance in the PD than the HC group in Elicitation and Repetition. Consistent with previous studies, a task effect was found; study participants demonstrated better performance in Repetition than in Elicitation. Results for the examination of perceptual ability in Experiment 2 revealed that PD and HC participants were equally successful in perceiving contrastive stress in Mandarin utterances produced by a healthy speaker.

Discussion

This study extended previous literature by measuring production and perception of contrastive stress in persons with PD who speak a tone language. Contrastive stress was detected with decreased accuracy in speech produced by persons with PD compared to healthy controls. However, performance was relatively preserved in a repetition condition compared to an elicitation condition. In contrast to the production results, speakers with PD were as successful as HC in perceiving sentential focus, consistent with previous research reporting a discrepancy between production and perception in persons with PD.

The semantic neural routes in contemporary models of visual word recognition are mainly constructed based on lexical-semantic processing. However, the neural bases of processing semantic cues embodied in sub-lexical units are less clear. The current fMRI study takes the ideographic property of Chinese characters (The semantic radical can provide a semantic cue for the character's meaning) to explore the brain mechanisms of sub-lexical semantic processing and its interaction with lexical-semantic processing in a lexical decision task. The GLM results and further ROI analysis revealed that the lexical-semantic processing relied on the left posterior Middle Temporal Gyrus (pMTG) and Angular Gyrus (AG); the sub-lexical semantic processing relied on the left middle MTG (mMTG) and AG; their integration relied on the left Anterior Temporal Lobe (ATL). It sheds light on investigating the neural circuit of the semantic processing in visual word reading.

For people to understand metaphors that require the creation of associations between remote concepts, both the diffuse spread of activation in semantic networks in the right hemisphere (coarse semantic coding) and the tight and focused spread of activation in the left hemisphere (fine semantic coding) are required. During adolescence, the dynamic between the left and right hemispheres that enables the processing of metaphors is not yet established. Thus, the present study aimed to (1) test whether left-hand muscle contractions that activate the right hemisphere's sensory-motor regions can boost metaphor comprehension in adolescents; (2) compare conventional and novel metaphor processing (with no muscle contractions) in adolescents and adults. For the first goal, 83 adolescents between the ages of 14–16 squeezed a rubber ball with either their right hands, left hands, or not at all (control group) while presented with two-word expressions of four types: literal expressions, conventional metaphors, novel metaphors, and unrelated expressions. Results showed that left-hand muscle contractions led to more accurate processing of literal expressions and conventional and novel metaphors. However, the over-activation of the right hemisphere led to a decreased ability to process unrelated expressions. For the second goal, the adolescent control group was compared with an adult group of participants. Results revealed that despite a general disadvantage in language processing (including conventional metaphors), adolescents were more accurate in processing novel metaphors. Our findings suggest that adolescents' left lateralization for language is not yet established, resulting in over-reliance on coarse semantic coding. In addition, our results demonstrate the effectiveness of a simple, non-invasive technique for enhancing metaphor comprehension in adolescents. This technique may especially benefit adolescents who struggle with metaphor comprehension, such as adolescents with autistic spectrum disorders or with poor social skills.

The way the brain does process language is an issue that has vexed the cognitive neuroscience of language for decades. Concurring with the Hickok and Poeppel's dual-stream network, we aimed to undertake a systematic review of the language-related functions of white matter tracts, comprising the dorsal and ventral language streams. Recent findings conform to an account in which ILF, IFOF, UF, ECF, a branch of the MLF, and a short segment of the SLF constitutes the ventral stream. The bulk of the SLF together with the AF form the dorsal language stream. The most anterior part of the dorsal pathway is also home to the FAT. We propose a fine-grained profile of each white matter fiber and the role in language processing. A better grasp of the architecture of language networks provides neuroclinicians and neurosurgeons precise pre/intraoperative instructions and a valuable avenue to better diagnose language impairments, and plan treatments.

The present study used a masked implicit priming paradigm to test if L1 to L2 translation occurs automatically and rapidly. Korean-English bilinguals performed a lexical decision task when English L2 targets (e.g., FACE) were translation equivalent to the L1 prime (얼굴 elkwul meaning ‘face’) or had phonological overlap with its translation to varying degrees: moderate (FAKE), minimal (FOOL), or unrelated. The translation equivalent targets resulted in N250 and N400 attenuation, reflecting facilitation in sublexical and lexical mapping of the target words, respectively. Crucially, target words which were phonologically related to the implicitly activated translation equivalent (face–FAKE/FOOL) also demonstrated N250/N400 modulation in the absence of semantic overlap. Additionally, the pattern of effects obtained against the unrelated condition differed between the implicitly related primes, with greater phonological overlap resulting in increased negativity, while minimal overlap led to attenuation. These findings suggest translation via direct lexical association occurring automatically at earlier stages of visual word recognition prior to lexical selection in bilinguals.

Speech perception skills have been implicated in the development of phoneme-graphene correspondence, yet the exact nature of speech perception and word reading ability remains unknown. We investigate phonological sensitivity to native (English) and nonnative (Spanish) speech syllables within an auditory oddball paradigm using event related potentials (ERPs) collected from lateral temporal electrode sites in 33 monolingual English-speaking children aged 6–8 years (N = 33). We further explore the relationship between ERPs to English word reading abilities for this group. Results revealed that language stimuli (English, Spanish), ERP condition (standard, deviant), and hemisphere (left, right) all influenced the lateral N1 component. ERPs recorded from deviant English stimuli were significantly more negative within the left hemisphere compared to all other recorded ERPs. Mean amplitude differences within the N1 in left lateral electrode sites recorded in response to English phoneme contrasts significantly predicted English word reading abilities within this sample. Results indicate that speech perception of native contrasts recorded in left temporal electrode sites for the N1 component are linked to English word reading abilities in early school-aged children.

Previous research has documented the impact of bilingualism on the functional connectivity (FC) of brain networks responsible for processing of two languages during a resting-state brain activity. However, the BOLD signal modulation during task-evoked neural activity remains unclear. To address this question we focused on language-related differences of fMRI-based FC of bilingual brains during morphosyntactic processing in L1 and L2 among balanced L1-Turkish-L2-Persian bilinguals who had learnt L2 at age 7. The task required grammaticality judgements to alternating L1-L2 sentences. In our previous study on the present dataset, we had demonstrated changes in BOLD activation in the Pars opercularis (PO), posterior Superior Temporal Gyrus (pSTG), Planum Temporale (PT), and Supplementary Motor Area (SMA), associated with auditory morphosyntactic processing. In the present reanalysis of these data we focused on FC within and between the language network and the control network. Regions of interest were based on the syntax- and control-specific regions activated by the task. Our findings confirm the FC between the syntax-specific regions PO and pSTG within the language network. The FC between these areas in the processing of morphosyntax turned to be quite similar for L1 and L2, reflecting the high competences of our balanced bilinguals in both languages. In the control network, direct FCs were found in two key areas of the PT and SMA (i.e. left PT to right PT and left PT to left SMA), supporting the view that these areas subserve control operations when bilinguals perceive and process spoken language. Remarkably, inter- and intra-hemispheric connectivities in the control network were indistinguishable for L1 and L2. Regarding intra-network results, although increased FCs were observed in L1 for the left PO-PT neurocircuit and in L2 for the pSTG-PT neurocircuit, none of them significantly interacted with grammaticality. Overall, these results suggest that being balanced bilingual with age of acquisition at 7 years appears to be associated with similarities of FC between syntax processing-related and input- and output-related brain networks. Considering that previous resting state studies had not found evidence for the above-mentioned connections in bilinguals, the present results indicate the importance of task-driven reconfigurations on functional connections between brain networks.

Although researchers often rely on group-level fMRI results to draw conclusions about the neurobiology of language, doing so without accounting for the complexities of individual brains may reduce the validity of our findings. Furthermore, understanding brain organization in individuals is critically important for both basic science and clinical translation. To assess the state of single-subject language localization in the functional neuroimaging literature, we carried out a systematic review of studies published through April 2020. Out of 977 papers identified through our search, 121 met our inclusion criteria for reporting single-subject fMRI results (fMRI studies of language in adults that report task-based single-subject statistics). Of these, 20 papers reported using a single-subject test-retest analysis to assess reliability. Thus, we found that a relatively modest number of papers reporting single-subject results quantified single-subject reliability. These varied substantially in acquisition parameters, task design, and reliability measures, creating significant challenges for making comparisons across studies. Future endeavors to optimize the localization of language networks in individuals will benefit from the standardization and broader reporting of reliability metrics for different tasks and acquisition parameters.

We examined the auditory sentence processing of neurologically unimpaired listeners and individuals with aphasia on canonical sentence structures in real-time using a visual-world eye-tracking paradigm. The canonical sentence constructions contained multiple noun phrases and an unaccusative verb, the latter of which formed a long-distance dependency link between the unaccusative verb and its single argument (which was base generated in the object position and then displaced to the subject position). To explore the likelihood of similarity-based interference during the real time linking of the verb and the sentence's subject noun, we manipulated the animacy feature of the noun phrases (matched or mismatched). The study's objectives were to examine whether (a) reducing the similarity-based interference by mismatching animacy features would modulate the encoding and retrieval dynamics of noun phrases in real-time; and (b) whether individuals with aphasia would demonstrate on time sensitivity to this lexical-semantic cue. Results revealed a significant effect of this manipulation in individuals both with and without aphasia. In other words, the mismatch in the representational features of the noun phrases increased the distinctiveness of the unaccusative verb's subject target at the time of syntactic retrieval (verb offset) for individuals in both groups. Moreover, individuals with aphasia were shown to be sensitive to the lexical-semantic cue, even though they appeared to process it slower than unimpaired listeners. This study extends to the cue-based retrieval model by providing new insight on the real-time mechanisms underpinning sentence comprehension.

Previous studies on the neuro-cognition of language have provided a strong case for systematic inter-individual variability in event-related potentials (ERPs) evoked during language processing. In the present study, we aimed at extending this evidence to the processing of morphologically complex words. We focused on German plural forms and tested two types of morphological violations: overapplications of regular plural morphemes (‘regularizations’) and of irregular plural morphemes (‘irregularizations’). The group-level results showed a biphasic LAN-P600 response for regularizations, and a P600 for irregularizations. In line with previous reports, our analyses of inter-individual variability suggested that biphasic responses consisting of a negativity followed by a positivity are unlikely to exist at the individual level. Importantly, when analyzing the scalp distribution of ERPs elicited in participants supposed to show negativity-dominant responses, we found this to vary as a function of the type of morphological form: regularizations elicited a left-hemisphere response (LAN), while irregularizations a more widespread negativity (N400). Our results are consistent with dual-route accounts of morphological processing that distinguish between rule-based processing for regular inflection and memory retrieval for irregular inflection. At a more general level, our study shows that complementing group-level results with analyses of inter-individual variability can crucially contribute to a more detailed understanding of brain signatures of language.