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Linguistic Complexity, Speech Production, and Comprehension in Parkinson’s Disease: Behavioral and Physiological Indices

Conclusions: These findings provide a novel window into the speech deficits associated with PD by examining performance on longer, sentence-level utterances in contrast to earlier investigations of single-word or nonword productions. Speech motor control processes and language comprehension were adversely affected in the majority of our participants with mild to moderate PD compared to the control group. Finally, increased syntactic complexity and sentence length affected both the healthy aging and PD groups’ speech production performance at the behavioral and kinematic levels.

from the Journal of Speech, Language, and Hearing Research

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Brain activation for language dual-tasking: Listening to two people speak at the same time and a change in network timing

The study used fMRI to investigate brain activation in participants who were able to listen to and successfully comprehend two people speaking at the same time (dual-tasking). The study identified brain mechanisms associated with high-level, concurrent dual-tasking, as compared with comprehending a single message. Results showed an increase in the functional connectivity among areas of the language network in the dual task. The increase in synchronization of brain activation for dual-tasking was brought about primarily by a change in the timing of left inferior frontal gyrus (LIFG) activation relative to posterior temporal activation, bringing the LIFG activation into closer correspondence with temporal activation. The results show that the change in LIFG timing was greater in participants with lower working memory capacity, and that recruitment of additional activation in the dual-task occurred only in the areas adjacent to the language network that was activated in the single task. The shift in LIFG activation may be a brain marker of how the brain adapts to high-level dual-tasking. Hum Brain Mapp, 2011. © 2011 Wiley-Liss, Inc.

from Human Brain Mapping

BOLD response to motion verbs in left posterior middle temporal gyrus during story comprehension

A primary focus within neuroimaging research on language comprehension is on the distribution of semantic knowledge in the brain. Studies have shown that the left posterior middle temporal gyrus (LPMT), a region just anterior to area MT/V5, is important for the processing of complex action knowledge. It has also been found that motion verbs cause activation in LPMT. In this experiment we investigated whether this effect could be replicated in a setting resembling real life language comprehension, i.e. without any overt behavioral task during passive listening to a story. During fMRI participants listened to a recording of the story “The Ugly Duckling”. We incorporated a nuisance elimination regression approach for factoring out known nuisance variables both in terms of physiological noise, sound intensity, linguistic variables and emotional content. Compared to the remaining text, clauses containing motion verbs were accompanied by a robust activation of LPMT with no other significant effects, consistent with the hypothesis that this brain region is important for processing motion knowledge, even during naturalistic language comprehension conditions.

from Brain and Language

Pitch Accents in Context: How Listeners Process Accentuation in Referential Communication

We investigated whether listeners are sensitive to (mis)matching accentuation patterns with respect to contrasts in the linguistic and visual context, using Event-Related Potentials. We presented participants with displays of two pictures followed by a spoken reference to one of these pictures (e.g., “the red ball”). The referent was contrastive with respect to the linguistic context (utterance in the previous trial: e.g., “the blue ball”) or with respect to the visual context (other picture in the display; e.g., a display with a red ball and a blue ball). The spoken reference carried a pitch accent on the noun (“the red BALL”) or on the adjective (“the RED ball”), or an intermediate (‘neutral’) accentuation. For the linguistic context, we found evidence for the Missing Accent Hypothesis: Listeners showed processing difficulties, in the form of increased negativities in the ERPs, for missing accents, but not for superfluous accents. ‘Neutral’ or intermediate accents were interpreted as ‘missing’ accents when they occurred late in the referential utterance, but not when they occurred early. For the visual context, we found evidence for the Missing Accent Hypothesis for a missing accent on the adjective (an increase in negativity in the ERPs) and a superfluous accent on the noun (no effect). However, a redundant color adjective (e.g., in the case of a display with a red ball and a red hat) led to less processing problems when the adjective carried a pitch accent.

from Neuropsychologia

Language comprehension vs. language production: Age effects on fMRI activation

Normal language acquisition is a process that unfolds with amazing speed primarily in the first years of life. However, the refinement of linguistic proficiency is an ongoing process, extending well into childhood and adolescence. An increase in lateralization and a more focussed productive language network have been suggested to be the neural correlates of this process. However, the processes underlying the refinement of language comprehension are less clear. Using a language comprehension (Beep Stories) and a language production (Vowel Identification) task in fMRI, we studied language representation and lateralization in 36 children, adolescents, and young adults (age 6–24 years). For the language comprehension network, we found a more focal activation with age in the bilateral superior temporal gyri. No significant increase of lateralization with age could be observed, so the neural basis of language comprehension as assessed with the Beep Stories task seems to be established in a bilateral network by late childhood. For the productive network, however, we could confirm an increase with age both in focus and lateralization. Only in the language comprehension task did verbal IQ correlate with lateralization, with higher verbal IQ being associated with more right-hemispheric involvement. In some subjects (24%), language comprehension and language production were lateralized to opposite hemispheres.

from Brain and Language

Dissociable neural imprints of perception and grammar in auditory functional imaging

In language processing, the relative contribution of early sensory and higher cognitive brain areas is still an open issue. A recent controversial hypothesis proposes that sensory cortices show sensitivity to syntactic processes, whereas other studies suggest a wider neural network outside sensory regions. The goal of the current event-related fMRI study is to clarify the contribution of sensory cortices in auditory syntactic processing in a 2 × 2 design. Two-word utterances were presented auditorily and varied both in perceptual markedness (presence or absence of an overt word category marking “-t”), and in grammaticality (syntactically correct or incorrect). A multivariate pattern classification approach was applied to the data, flanked by conventional cognitive subtraction analyses. The combination of methods and the 2 × 2 design revealed a clear picture: The cognitive subtraction analysis found initial syntactic processing signatures in a neural network including the left IFG, the left aSTG, the left superior temporal sulcus (STS), as well as the right STS/STG. Classification of local multivariate patterns indicated the left-hemispheric regions in IFG, aSTG, and STS to be more syntax-specific than the right-hemispheric regions. Importantly, auditory sensory cortices were only sensitive to the overt perceptual marking, but not to the grammaticality, speaking against syntax-inflicted sensory cortex modulations. Instead, our data provide clear evidence for a distinction between regions involved in pure perceptual processes and regions involved in initial syntactic processes. Hum Brain Mapp, 2011. © 2011 Wiley-Liss, Inc.

from Human Brain Mapping

Severe Traumatic Brain Injury, Frontal Lesions, and Social Aspects of Language Use: A Study of French-Speaking Adults

The purpose of this study was to gain insight into the social (pragmatic) aspects of language use by French-speaking individuals with frontal lesions following a severe traumatic brain injury. Eleven participants with traumatic brain injury performed tasks in three areas of communication: production (interview situation), comprehension (direct requests, conventional indirect requests, and hints), and metapragmatic knowledge. The results of the patients pointed out some strengths (turn-taking in production, and request comprehension, including hints and the speaker’s intention) and some weaknesses (topic maintenance in production and metapragmatic knowledge). The patients’ good comprehension of requests and their difficulty expressing metapragmatic knowledge suggests that they differ from controls in how they “explain the world”: their knowledge of the event sequence was not based on verbally expressible knowledge about the relationship between the structural characteristics of a request utterance and those of its social production context. The pragmatic skills of persons with traumatic brain injury seem to vary across tasks: these individuals have specific strengths and weaknesses in different domains. In addition, marked interindividual differences were noted among the patients: three of them had only one weak point, topic maintenance. These interindividual differences were not systematically linked to performance on executive function tests, but lesion unilaterality (right or left) seems to help preserve patients’ pragmatic and metapragmatic skills. The discussion stresses the need to take each patient’s strengths and weaknesses into account in designing remediation programs.

from the Journal of Communication Disorders

Linguistic difficulties in children and adolescents after acquired brain injury: A retrospective study

This study confirms that word retrieval is an area of deficit in many children with acquired brain injuries one year or more after the injury occurred. The study also indicates that children with TBI may have persistent deficits in comprehension of both vocabulary and grammar.<p><p>from the <a href=”Journal” _mce_href=”http://iospress.metapress.com/content/p01087313126v551/”><em>Journal”>http://iospress.metapress.com/content/p01087313126v551/”><em>Journal of Pediatric Rehabilitation Medicine</em></a></p>

Neural correlates of language comprehension in autism spectrum disorders: When language conflicts with world knowledge

In individuals with ASD, difficulties with language comprehension are most evident when higher-level semantic-pragmatic language processing is required, for instance when context has to be used to interpret the meaning of an utterance. Until now, it is unclear at what level of processing and for what type of context these difficulties in language comprehension occur. Therefore, in the current fMRI study, we investigated the neural correlates of the integration of contextual information during auditory language comprehension in 24 adults with ASD and 24 matched control participants. Different levels of context processing were manipulated by using spoken sentences that were correct or contained either a semantic or world knowledge anomaly. Our findings demonstrated significant differences between the groups in inferior frontal cortex that were only present for sentences with a world knowledge anomaly. Relative to the ASD group, the control group showed significantly increased activation in left inferior frontal gyrus (LIFG) for sentences with a world knowledge anomaly compared to correct sentences. This effect possibly indicates reduced integrative capacities of the ASD group. Furthermore, world knowledge anomalies elicited significantly stronger activation in right inferior frontal gyrus (RIFG) in the control group compared to the ASD group. This additional RIFG activation probably reflects revision of the situation model after new, conflicting information. The lack of recruitment of RIFG is possibly related to difficulties with exception handling in the ASD group.

from Neuropsychologia

How vision is shaped by language comprehension – top-down feedback based on low-spatial frequencies

Effects of language comprehension on visual processing have been extensively studied within the embodied-language framework. However, it is unknown whether these effects are caused by passive repetition suppression in visual processing areas, or depend on active feedback, based on partial input, from prefrontal regions. Based on a model of top-down feedback during visual recognition, we predicted diminished effects when low-spatial frequencies were removed from targets. We compared low-pass and high-pass filtered pictures in a sentence-picture-verification task. Target pictures matched or mismatched the implied shape of an object mentioned in a preceding sentence, or were unrelated to the sentences. As predicted, there was a large match advantage when the targets contained low-spatial frequencies, but no effect of linguistic context when these frequencies were filtered out. The proposed top-down feedback model is superior to repetition suppression in explaining the current results, as well as earlier results as well as about the lateralization of this effect, and peculiar color match effects. We discuss these findings in the context of recent general proposals of prediction and top-down feedback.

from Brain Research

Bilingualism influences inhibitory control in auditory comprehension

Bilinguals have been shown to outperform monolinguals at suppressing task-irrelevant information. The present study aimed to identify how processing linguistic ambiguity during auditory comprehension may be associated with inhibitory control. Monolinguals and bilinguals listened to words in their native language (English) and identified them among four pictures while their eye-movements were tracked. Each target picture (e.g., hamper) appeared together with a similar-sounding within-language competitor picture (e.g., hammer) and two neutral pictures. Following each eye-tracking trial, priming probe trials indexed residual activation of target words, and residual inhibition of competitor words. Eye-tracking showed similar within-language competition across groups; priming showed stronger competitor inhibition in monolinguals than in bilinguals, suggesting differences in how inhibitory control was used to resolve within-language competition. Notably, correlation analyses revealed that inhibition performance on a nonlinguistic Stroop task was related to linguistic competition resolution in bilinguals but not in monolinguals. Together, monolingual-bilingual comparisons suggest that cognitive control mechanisms can be shaped by linguistic experience.

from Cognition

Conflicts in language processing: a new perspective on the N400-P600 distinction

Conflicts in language processing often correlate with late positive event-related brain potentials (ERPs), particularly when they are induced by inconsistencies between different information types (e.g. syntactic and thematic/plausibility information). However, under certain circumstances, similar sentence-level interpretation conflicts (inanimate subjects) engender negativity effects (N400 s) instead. The present ERP study was designed to shed light on this inconsistency. In previous studies showing monophasic positivities (P600 s), the conflict was irresolvable and induced via a verb, whereas N400 s were elicited by resolvable, argument-induced conflicts. Here, we therefore examined irresolvable argument-induced conflicts (pronoun case violations) in simple English sentences. Conflict strength was manipulated via the animacy of the first argument and the agreement status of the verb. Processing conflicts engendered a biphasic N400-late positivity pattern, with only the N400 sensitive to conflict strength (animacy). These results suggest that argument-induced conflicts engender N400 effects, (which we interpret in terms of increased competition for the Actor role) whereas irresolvable conflicts elicit late positivities (which we interpret as reflecting well-formedness categorisation).

from Neuropsychologia

Listening to the sound of silence: Investigating the consequences of disfluent silent pauses in speech for listeners

Silent pauses are a common form of disfluency in speech yet little attention has been paid to them in the psycholinguistic literature. The present paper investigates the consequences of such silences for listeners, using an Event-Related Potential (ERP) paradigm. Participants heard utterances ending in predictable or unpredictable words, some of which included a disfluent silence before the target. In common with previous findings using er disfluencies, the N400 difference between predictable and unpredictable words was attenuated for the utterances that included silent pauses, suggesting a reduction in the relative processing benefit for predictable words. An earlier relative negativity, topographically distinct from the N400 effect and identifiable as a Phonological Mismatch Negativity (PMN), was found for fluent utterances only. This suggests that only in the fluent condition did participants perceive the phonology of unpredictable words to mismatch with their expectations. By contrast, for disfluent utterances only, unpredictable words gave rise to a late left frontal positivity, an effect previously observed following er s and disfluent repetitions. We suggest that this effect reflects the engagement of working memory processes that occurs when fluent speech is resumed. Using a surprise recognition memory test, we also show that listeners were more likely to recognise words which had been encountered after silent pauses, demonstrating that silence affects not only the process of language comprehension but also its eventual outcome. We argue that, from a listener’s perspective, one critical feature of disfluency is the temporal delay which it adds to the speech signal.

from Neuropsychologia

Effects of event knowledge in processing verbal arguments

This research tests whether comprehenders use their knowledge of typical events in real time to process verbal arguments. In self-paced reading and event-related brain potential (ERP) experiments, we used materials in which the likelihood of a specific patient noun (brakes or spelling) depended on the combination of an agent and verb (mechanic checked vs. journalist checked). Reading times were shorter at the word directly following the patient for the congruent than the incongruent items. Differential N400s were found earlier, immediately at the patient. Norming studies ruled out any account of these results based on direct relations between the agent and patient. Thus, comprehenders dynamically combine information about real-world events based on intrasentential agents and verbs, and this combination then rapidly influences online sentence interpretation.

from the Journal of Memory and Language

Age-related and individual differences in the use of prediction during language comprehension

During sentence comprehension, older adults are less likely than younger adults to predict features of likely upcoming words. A pair of experiments assessed whether such differences would extend to tasks with reduced working memory demands and time pressures. In Experiment 1, event-related brain potentials were measured as younger and older adults read short phrases cuing antonyms or category exemplars, followed three seconds later by targets that were either congruent or incongruent and, for congruent category exemplars, of higher or lower typicality. When processing the less expected low typicality targets, younger – but not older – adults elicited a prefrontal positivity (500–900 ms) that has been linked to processing consequences of having predictions disconfirmed. Thus, age-related changes in prediction during comprehension generalize across task circumstances. Analyses of individual differences revealed that older adults with higher category fluency were more likely to show the young-like pattern. Experiment 2 showed that these age-related differences were not due to simple slowing of language production mechanisms, as older adults generated overt responses to the cues as quickly as – and more accurately than – younger adults. However, older adults who were relatively faster to produce category exemplars in Experiment 2 were more likely to have shown predictive processing patterns in Experiment 1. Taken together, the results link prediction during language comprehension to language production mechanisms and suggest that although older adults can produce speeded language output on demand, they are less likely to automatically recruit these mechanisms during comprehension unless top-down circuitry is particularly strong.

from Brain and Language