Journal of Neurolinguistics最新文献

Background

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders worldwide and is characterized by problems with cognition and language, especially word-finding difficulties. The present study focuses on lexical-semantic features via five discourse variables reflecting word-finding difficulties, namely indefinite terms, lexical frequency, repetitions, semantic paraphasias, and use of pronouns. Our aim is twofold: testing whether these variables can discriminate healthy aging from AD, but also mild from moderate AD.

Method

105 participants were examined from the existing Pitt corpus (available on DementiaBank), which includes the Cookie Theft Picture Description task. 40 participants were healthy controls, 25 were mild AD participants, and 40 moderate AD participants.

Results

The moderate AD group differed significantly from healthy controls in terms of indefinite terms, repetitions, semantic paraphasias, and pronouns. For the latter variable, mild AD patients also differed significantly from healthy controls. However, none of the variables could differentiate mild from moderate AD.

Conclusion

Four out of five discourse variables could discriminate healthy aging from moderate AD, while only one could discriminate mild AD patients. This is therefore questioning current literature on connected-speech measures in AD and calling for further research on the variables that could better distinguish mild to moderate AD.

In the intense debate about the potential benefits of bilingual experience to executive functioning (EF), little research addresses the possibility that the benefits may manifest in the process of adapting to an EF task. In this study, we hypothesize that interpreters, confronted frequently with more intense interference from different languages, may adapt to the interference task more efficiently. With the event-related potential (ERP) technique, this study examined whether participants with interpreting experience may adapt to the conflicting environment of a Flanker task more efficiently than non-interpreter bilinguals with the progression of the task (i.e., from the first to the second half trials). Our results showed that the interpreter group showed better conflict resolution (i.e., a lower error rate) despite being less active in early attentional processing (i.e., less negative overall N1 and N2 amplitudes). Second, both groups showed an adaptation effect in the second half trials compared with the first half, as reflected by less negative overall N2 amplitude and more positive overall P3 amplitude. More importantly, only the interpreter group showed an additional benefit in adaptation, as reflected by an earlier overall P3 peak latency in the second half trials. Taken together, the results offered some support for an interpreter advantage in the dynamics of adapting to the Flanker task, which could provide new insight into the effect of bilingual experience on non-verbal interference control.

A comprehensive neural model of language must accommodate four components: representations, operations, structures and encoding. Recent intracranial research has begun to map out the feature space associated with syntactic processes, but the field lacks a unified framework that can direct invasive neural analyses. This article proposes a neurocomputational architecture for syntax, termed ROSE (Representation, Operation, Structure, Encoding). Under ROSE, the basic data structures of syntax are atomic features, types of mental representations (R), and are coded at the single-unit and ensemble level. Operations (O) transforming these units into manipulable objects accessible to subsequent structure-building levels are coded via high frequency broadband γ activity. Low frequency synchronization and cross-frequency coupling code for recursive structural inferences (S). Distinct forms of low frequency coupling encode these structures onto distinct workspaces (E). Causally connecting R to O is spike-phase/LFP coupling; connecting O to S is phase-amplitude coupling; connecting S to E are frontotemporal traveling oscillations. ROSE is reliant on neurophysiologically plausible mechanisms and provides an anatomically precise and falsifiable grounding for natural language syntax.

A puzzling finding in the speech production literature is the facilitation of categorically related distractors in a superordinate level naming task. The context is in this case response congruent, because application of the task instruction to the context would lead to the correct response. This study investigates the time-course of response congruence effects in speech production using event-related potentials (ERPs). Participants overtly named target words that were overlaid on context pictures with either their superordinate category level name or their associated function, while their response times and ERPs were recorded. Behavioural results replicate the facilitating effect of response congruence. The ERP results showed that the N2 was larger for a response incongruent than congruent context, and this effect correlated with the behavioural pattern of results. This key finding suggests that response incongruence is associated with a conflict-monitoring response which drives the behavioural effect. Further, N400 amplitude was not modulated by response congruence, showing that its effect appears confined to the conceptualisation phase. Finally, P3 modulations mirrored those in RTs, but unlike the N2 effect, they did not correlate with RTs. This suggests that, although the facilitating effect of response congruence is confined to the conceptualisation phase of speech production, response incongruent representations may remain active during later processing stages, or that this late effect of response congruence reflects conflict resolve. Implications for models of speech production are discussed.

Adjectives (e.g., hungry) are an important part of language, but have been little studied in individuals with impaired language. Adjectives are used in two different ways in English: attributively, to modify a noun (the hungry dog); or predicatively, after a verb (the dog is hungry). Attributive adjectives have a more complex grammatical structure than predicative adjectives, and may therefore be particularly prone to disruption in individuals with grammatical impairments. We investigated adjective production in three subtypes of primary progressive aphasia (PPA: agrammatic, semantic, logopenic), as well as in agrammatic stroke aphasia and a group of healthy control participants. Participants produced narratives based on picture books, and we coded every adjective they produced for its syntactic structure. Compared to healthy controls, the two agrammatic groups, but not the other two patient groups, produced significantly fewer attributive adjectives per sentence. All four patient groups were similar to controls for their rate of predicative adjective production. In addition, we found a significant correlation in the agrammatic PPA participants between their rate of producing attributive adjectives and impaired production of sentences with complex syntactic structure (subject cleft sentences like It was the boy that chased the girl); no such correlation was found for predicative adjectives. Irrespective of structure, we examined the lexical characteristics of the adjectives that were produced, including length, frequency, semantic diversity and neighborhood density. Overall, the lexical characteristics of the produced adjectives were largely consistent with the language profile of each group. In sum, the results suggest that attributive adjectives present a particular challenge for individuals with agrammatic language production, and add a new dimension to the description of agrammatism. Our results further suggest that attributive adjectives may be a fruitful target for improved treatment and recovery of agrammatic language.

Over the past decades, focus has been on developing methods that allow tapping into aspects of cognition that are not directly observable. This includes linguistic knowledge and skills which develop largely without awareness and may therefore be difficult or impossible to articulate. Building on the relation between language cognition and the nervous system, we examine whether Heart Rate Variability (HRV), a cardiovascular measure that indexes Autonomic Nervous System activity, can be used to assess implicit language knowledge. We test the potential of HRV to detect whether individuals possess grammatical knowledge and explore how sensitive the cardiovascular response is.

41 healthy, British English-speaking adults listened to 40 English speech samples, half of which contained grammatical errors. Thought Technology's 5-channel ProComp 5 encoder tracked heart rate via a BVP-Flex/Pro sensor attached to the middle finger of the non-dominant hand, at a rate of 2048 samples per second. A Generalised Additive Mixed Effects Model confirmed a cardiovascular response to grammatical violations: there is a statistically significant reduction in HRV as indexed by NN50 in response to stimuli that contain errors. The cardiovascular response reflects the extent of the linguistic violations, and NN50 decreases linearly with an increase in the number of errors, up to a certain level, after which HRV remains constant.

This observation brings into focus a new dimension of the intricate relationship between physiology and cognition. Being able to use a highly portable and non-intrusive technique with language stimuli also creates exciting possibilities for assessing the language knowledge of individuals from a range of populations in their natural environment and in authentic communicative situations.

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.