Vascular responses to syntactic processing: event-related fMRI study of relative clauses

Neural correlates of semantic-driven syntactic parsing in sentence comprehension

For sentence comprehension, information carried by semantic relations between constituents must be combined with other information to decode the constituent structure of a sentence, due to atypical and noisy situations of language use. Neural correlates of decoding sentence structure by semantic information have remained largely unexplored. In this functional MRI study, we examine the neural basis of semantic-driven syntactic parsing during sentence reading and compare it with that of other types of syntactic parsing driven by word order and case marking. Chinese transitive sentences of various structures were investigated, differing in word order, case making, and agent-patient semantic relations (i.e., same vs. different in animacy). For the non-canonical unmarked sentences without usable case marking, a semantic-driven effect triggered by agent-patient ambiguity was found in the left inferior frontal gyrus opercularis (IFGoper) and left inferior parietal lobule, with the activity not being modulated by naturalness factors of the sentences. The comparison between each type of non-canonical sentences with canonical sentences revealed that the non-canonicity effect engaged the left posterior frontal and temporal regions, in line with previous studies. No extra neural activity was found responsive to case marking within the non-canonical sentences. A word order effect across all types of sentences was also found in the left IFGoper, suggesting a common neural substrate between different types of parsing. The semantic-driven effect was also observed for the non-canonical marked sentences but not for the canonical sentences, suggesting that semantic information is used in decoding sentence structure in addition to case marking. The current findings illustrate the neural correlates of syntactic parsing with semantics, and provide neural evidence of how semantics facilitates syntax together with other information.

Fractionating difficulty during sentence comprehension using functional neuroimaging

Sentence comprehension is highly practiced and largely automatic, but this belies the complexity of the underlying processes. We used functional neuroimaging to investigate garden-path sentences that cause difficulty during comprehension, in order to unpack the different processes used to support sentence interpretation. By investigating garden-path and other types of sentences within the same individuals, we functionally profiled different regions within the temporal and frontal cortices in the left hemisphere. The results revealed that different aspects of comprehension difficulty are handled by left posterior temporal, left anterior temporal, ventral left frontal, and dorsal left frontal cortices. The functional profiles of these regions likely lie along a spectrum of specificity to generality, including language-specific processing of linguistic representations, more general conflict resolution processes operating over linguistic representations, and processes for handling difficulty in general. These findings suggest that difficulty is not unitary and that there is a role for a variety of linguistic and non-linguistic processes in supporting comprehension.

Functional near-infrared spectroscopy shows that object relative clauses are more difficult to process than subject relative clauses in Turkish

It was suggested that processing subject relative clauses (SRCs) is universally easier than processing object relative clauses (ORCs) based on the studies carried out in head-initial languages such as English and German. However, studies in head-final languages such as Chinese and Basque contradicted this claim. Turkish is also a head-final language. Existing relative clause processing literature in Turkish is based solely on behavioural metrics. Even though an ORC processing disadvantage was suggested for Turkish, the results were not conclusive. Therefore, we aimed to investigate the neural dynamics of relative clause processing in Turkish. We asked 14 native Turkish speakers to answer yes/no questions about 24 sentences each containing either a SRC or ORC while their prefrontal hemodynamic activity was recorded with functional near-infrared spectroscopy. Our findings revealed hemodynamic activity in the lateral portions of the left prefrontal cortex for both conditions. However, hemodynamic activity was more widespread in prefrontal regions in ORC compared to SRC condition. Even though the behavioural metrics failed to produce a significant difference between the conditions, direct ORC > SRC contrast revealed significant activity in the left inferior frontal cortex, a region heavily involved in language processing, as well as in left and right dorsolateral prefrontal cortices, which are also known to be involved in language processing-related and conflict monitoring-related processes, respectively. Our findings indicate that processing ORCs is more difficult and requires further prefrontal resources than processing SRCs in Turkish, thus refuting the head-directionality-based explanations of relative clause processing asymmetries.

Lexico-Semantic Influence on Syntactic Processing: An Eye-Tracking Study with Spanish Relative Clauses

This paper investigates the interaction between lexicosemantic and syntactic information in sentence processing by examining the online comprehension of Spanish relative clauses (RCs) of both restrictive and non-restrictive types. A corpus study shows that, in Spanish, a RC may be introduced by different function words (called relativizers), which differ in lexical frequency, as well as semantic features. Based on these facts, an eye-tracking experiment was conducted with the aim of analyzing whether lexicosemantic information could influence sentence processing at the early stages. The results report an early influence of lexicosemantic information not only when activating a relativizer but also when integrating it within the syntactic structure. Additionally, the semantic role played by each RC type seems to constrain sentence processing at different regions. Our results favor an interactive view of language processing, according to which language comprehension is guided from the early stages by different kinds of linguistic information rather than syntactic information alone.

A subject relative clause preference in a split-ergative language: ERP evidence from Georgian

A fascinating descriptive property of human language processing whose explanation is still debated is that subject-gap relative clauses are easier to process than object-gap relative clauses, across a broad range of languages with different properties. However, recent work suggests that this generalization does not hold in Basque, an ergative language, and has motivated an alternative generalization in which the preference is for gaps in morphologically unmarked positions-subjects in nominative-accusative languages, and objects and intransitive subjects in ergative-absolutive languages. Here we examined whether this generalization extends to another ergative-absolutive language, Georgian. ERP and self-paced reading results show a large anterior negativity and slower reading times when a relative clause is disambiguated to an object relative vs a subject relative. These data thus suggest that in at least some ergative-absolutive languages, the classic descriptive generalization-that object relative clauses are more costly than subject relative clauses-still holds.

Revisiting the relation between syntax, action, and left BA44

Among the many lines of research that have been exploring how embodiment contributes to cognition, one focuses on how the neural substrates of language may be shared, or at least closely coupled, with those of action. This paper revisits a particular proposal that has received considerable attention-namely, that the forms of hierarchical sequencing that characterize both linguistic syntax and goal-directed action are underpinned partly by common mechanisms in left Brodmann area (BA) 44, a cortical region that is not only classically regarded as part of Broca's area, but is also a core component of the human Mirror Neuron System. First, a recent multi-participant, multi-round debate about this proposal is summarized together with some other relevant findings. This review reveals that while the proposal is supported by a variety of theoretical arguments and empirical results, it still faces several challenges. Next, a narrower application of the proposal is discussed, specifically involving the basic word order of subject (S), object (O), and verb (V) in simple transitive clauses. Most languages are either SOV or SVO, and, building on prior work, it is argued that these strong syntactic tendencies derive from how left BA44 represents the sequential-hierarchical structure of goal-directed actions. Finally, with the aim of clarifying what it might mean for syntax and action to have "common" neural mechanisms in left BA44, two different versions of the main proposal are distinguished. Hypothesis 1 states that the very same neural mechanisms in left BA44 subserve some aspects of hierarchical sequencing for syntax and action, whereas Hypothesis 2 states that anatomically distinct but functionally parallel neural mechanisms in left BA44 subserve some aspects of hierarchical sequencing for syntax and action. Although these two hypotheses make different predictions, at this point neither one has significantly more explanatory power than the other, and further research is needed to elaborate and test them.

Syntactic and Semantic Influences on the Time Course of Relative Clause Processing: The Role of Language Dominance

We conducted a visual world eye-tracking experiment with highly proficient Spanish-English bilingual adults to investigate the effects of relative language dominance, operationalized as a continuous, multidimensional variable, on the time course of relative clause processing in the first-learned language, Spanish. We found that participants exhibited two distinct processing preferences: a semantically driven preference to assign agency to referents of lexically animate noun phrases and a syntactically driven preference to interpret relative clauses as subject-extracted. Spanish dominance was found to exert a distinct influence on each of these preferences, gradiently attenuating the semantic preference while gradiently exaggerating the syntactic preference. While these results might be attributable to particular properties of Spanish and English, they also suggest a possible generalization that greater dominance in a language increases reliance on language-specific syntactic processing strategies while correspondingly decreasing reliance on more domain-general semantic processing strategies.

The cortical organization of listening effort: New insight from functional near-infrared spectroscopy

Everyday challenges impact our ability to hear and comprehend spoken language with ease, such as accented speech (source factors), spectral degradation (transmission factors), complex or unfamiliar language use (message factors), and predictability (context factors). Auditory degradation and linguistic complexity in the brain and behavior have been well investigated, and several computational models have emerged. The work here provides a novel test of the hypotheses that listening effort is partially reliant on higher cognitive auditory attention and working memory mechanisms in the frontal lobe, and partially reliant on hierarchical linguistic computation in the brain's left hemisphere. We specifically hypothesize that these models are robust and can be applied in ecologically relevant and coarse-grain contexts that rigorously control for acoustic and linguistic listening challenges. Using functional near-infrared spectroscopy during an auditory plausibility judgment task, we show the hierarchical cortical organization for listening effort in the frontal and left temporal-parietal brain regions. In response to increasing levels of cognitive demand, we found (i) poorer comprehension, (ii) slower reaction times, (iii) increasing levels of perceived mental effort, (iv) increasing levels of brain activity in the prefrontal cortex, (v) hierarchical modulation of core language processing regions that reflect increasingly higher-order auditory-linguistic processing, and (vi) a correlation between participants' mental effort ratings and their performance on the task. Our results demonstrate that listening effort is partly reliant on higher cognitive auditory attention and working memory mechanisms in the frontal lobe and partly reliant on hierarchical linguistic computation in the brain's left hemisphere. Further, listening effort is driven by a voluntary, motivation-based attention system for which our results validate the use of a single-item post-task questionnaire for measuring perceived levels of mental effort and predicting listening performance. We anticipate our study to be a starting point for more sophisticated models of listening effort and even cognitive neuroplasticity in hearing aid and cochlear implant users.

Effect of corpus callosum agenesis on the language network in children and adolescents

The present study is interested in the role of the corpus callosum in the development of the language network. We, therefore, investigated language abilities and the language network using task-based fMRI in three cases of complete agenesis of the corpus callosum (ACC), three cases of partial ACC and six controls. Although the children with complete ACC revealed impaired functions in specific language domains, no child with partial ACC showed a test score below average. As a group, ACC children performed significantly worse than healthy controls in verbal fluency and naming. Furthermore, whole-brain ROI-to-ROI connectivity analyses revealed reduced intrahemispheric and right intrahemispheric functional connectivity in ACC patients as compared to controls. In addition, stronger functional connectivity between left and right temporal areas was associated with better language abilities in the ACC group. In healthy controls, no association between language abilities and connectivity was found. Our results show that ACC is associated not only with less interhemispheric, but also with less right intrahemispheric language network connectivity in line with reduced verbal abilities. The present study, thus, supports the excitatory role of the corpus callosum in functional language network connectivity and language abilities.

The role of the corpus callosum in language network connectivity in children

The specific role of the corpus callosum (CC) in language network organization remains unclear, two contrasting models have been proposed: inhibition of homotopic areas allowing for independent functioning of the hemispheres versus integration of information from both hemispheres. This study aimed to add to this discussion with the first investigation of language network connectivity in combination with CC volume measures. In 38 healthy children aged 6–12, we performed task‐based functional magnetic resonance imaging to measure language network connectivity, used structural magnetic resonance imaging to quantify CC subsection volumes, and administered various language tests to examine language abilities. We found an increase in left intrahemispheric and bilateral language network connectivity and a decrease in right intrahemispheric connectivity associated with larger volumes of the posterior, mid‐posterior, and central subsections of the CC. Consistent with that, larger volumes of the posterior parts of the CC were significantly associated with better verbal fluency and vocabulary, the anterior CC volume was positively correlated with verbal span. Thus, children with larger volumes of CC subsections showed increased interhemispheric language network connectivity and were better in different language domains. This study presents the first evidence that the CC is directly linked to language network connectivity and underlines the excitatory role of the CC in the integration of information from both hemispheres.

Neural architecture of human language: Hierarchical structure building is independent from working memory

Using functional magnetic resonance imaging (fMRI), we show that the neural substrate of language does not overlap with that for verbal working memory when we carefully define verbal working memory in sentence processing. Object-Subject-Verb (OSV) sentences in Japanese were contrasted with canonical Subject-Object-Verb (SOV) sentences, which had less hierarchy in linguistic structure. This contrast revealed the posterior part of Broca's area and the left posterior middle temporal gyrus (pMTG) as the neural bases for hierarchical structure building. Furthermore, we changed verbal working memory load in OSV sentences by adding modifiers to the subject or object noun phrases; this resulted in the activation in the op9, which is situated in the frontal operculum and is adjacent to, but not situated in, Broca's area. The neuroanatomical segregation of language processing from verbal working memory suggests independence of the faculty of language from the verbal working memory system, providing evidence for the domain-specificity of language in human cognition.

Neural substrates of word category information as the basis of syntactic processing

The ability to use word category information (WCI) for syntactic structure building has been hypothesized to be the essence of human language faculty. The neural substrate of the ability of using the WCI for the complex syntactic hierarchical structure processing, however, is yet unknown. Therefore, we directly conducted an fMRI experiment by using a pseudo-Chinese artificial language with syntactic structures containing a center-embedded relative clause. Thirty non-Chinese native (Korean) speakers were randomly divided into two groups: one acquired WCI and WCI-based syntactic rules (the WCI group) before the scanning session, and the other did not (the non-WCI group). Both groups were required to judge the grammaticality of the testing sentences, with critical long-distance dependencies between two elements (the main verb and the relativizer). Behaviorally, the WCI group's accuracy was significantly higher and its reaction time was shorter. The scanning results showed that the left superior temporal gyrus (STG) and Broca's area were more strongly activated for the WCI group, and the dynamic causal modeling analyses revealed a distinct effective connectivity pattern for this group. Therefore, the present research, for the first time, reveals that the activation of and the functional connectivity between Broca's area and the left STG play a critical role in the ability of the rule-based use of the WCI which is crucial for complex hierarchical structure building, and might be substantially corresponding to the "labeling competence" within the linguistic framework.

Weaker semantic language lateralization associated with better semantic language performance in healthy right-handed children

INTRODUCTION

The relationship between language abilities and language lateralization in the developing brain is important for our understanding of the neural architecture of language development.

METHODS

We investigated 35 right-handed children and adolescents aged 7-16 years with a functional magnetic resonance imaging language paradigm and a comprehensive language and verbal memory examination.

RESULTS

We found that less lateralized language was significantly correlated with better language performance across areas of the brain and across different language tasks. Less lateralized language in the overall brain was associated with better in-scanner task accuracy on a semantic language decision task and out-of-scanner vocabulary and verbal fluency. Specifically, less lateralized frontal lobe language dominance was associated with better in-scanner task accuracy and out-of-scanner verbal fluency. Furthermore, less lateralized parietal language was associated with better out-of-scanner verbal memory across learning, short- and long-delay trials. In contrast, we did not find any relationship between temporal lobe language laterality and verbal performance.

CONCLUSIONS

This study suggests that semantic language performance is better with some involvement of the nondominant hemisphere.

Effects of Age and Location in Chinese Relative Clauses Processing

Three experiments investigated Chinese relative clause processing with children, youths and elders using sentence-picture matching and self-paced reading methods. In Experiment 1, we found that object-extracted clause were easier to comprehend than subject-extracted clause , and object-modified relative clause (i.e., object-modified subject-extracted clause[Formula: see text]object-modified object-extracted clause) were difficult to comprehend than subject modified relative clause (subject-modified subject-extracted clause[Formula: see text]subject-modified object-extracted clause). Importantly, this paper also found 5-6.5 ages may be critical for children to comprehend RCs in Chinese. Experiment 2 also showed that S-ORCs were easier to comprehend than S-SRCs for youths and elders. Further, elders have more difficulty comprehending RCs than youths. Experiment 3 indicated that there were no significant differences in difficulty between O-SRCs and O-ORCs, and no differences were found between youths and elders. In general, our findings gave support to predictions of working memory-based theory, and also indicated that RCs processing has an intricate course. Many factors such as syntactic, language specificity, experience, personality, must all be considered in sentence processing.

From Mimicry to Language: A Neuroanatomically Based Evolutionary Model of the Emergence of Vocal Language

The auditory cortex communicates with the frontal lobe via the middle temporal gyrus (auditory ventral stream; AVS) or the inferior parietal lobule (auditory dorsal stream; ADS). Whereas the AVS is ascribed only with sound recognition, the ADS is ascribed with sound localization, voice detection, prosodic perception/production, lip-speech integration, phoneme discrimination, articulation, repetition, phonological long-term memory and working memory. Previously, I interpreted the juxtaposition of sound localization, voice detection, audio-visual integration and prosodic analysis, as evidence that the behavioral precursor to human speech is the exchange of contact calls in non-human primates. Herein, I interpret the remaining ADS functions as evidence of additional stages in language evolution. According to this model, the role of the ADS in vocal control enabled early Homo (Hominans) to name objects using monosyllabic calls, and allowed children to learn their parents' calls by imitating their lip movements. Initially, the calls were forgotten quickly but gradually were remembered for longer periods. Once the representations of the calls became permanent, mimicry was limited to infancy, and older individuals encoded in the ADS a lexicon for the names of objects (phonological lexicon). Consequently, sound recognition in the AVS was sufficient for activating the phonological representations in the ADS and mimicry became independent of lip-reading. Later, by developing inhibitory connections between acoustic-syllabic representations in the AVS and phonological representations of subsequent syllables in the ADS, Hominans became capable of concatenating the monosyllabic calls for repeating polysyllabic words (i.e., developed working memory). Finally, due to strengthening of connections between phonological representations in the ADS, Hominans became capable of encoding several syllables as a single representation (chunking). Consequently, Hominans began vocalizing and mimicking/rehearsing lists of words (sentences).

Right is not always wrong: DTI and fMRI evidence for the reliance of reading comprehension on language-comprehension networks in the right hemisphere

The Simple View theory suggests that reading comprehension relies on automatic recognition of words combined with language comprehension. The goal of the current study was to examine the structural and functional connectivity in networks supporting reading comprehension and their relationship with language comprehension within 7-9 year old children using Diffusion Tensor Imaging (DTI) and fMRI during a Sentence Picture Matching task. Fractional Anisotropy (FA) values in the left and right Inferior Longitudinal Fasciculus (ILF) and Superior Longitudinal Fasciculus (SLF), known language-related tracts, were correlated from DTI data with scores from the Woodcock-Johnson III (WJ-III) Passage Comprehension sub-test. Brodmann areas most proximal to white-matter regions with significant correlation to Passage Comprehension scores were chosen as Regions-of-Interest (ROIs) and used as seeds in a functional connectivity analysis using the Sentence Picture Matching task. The correlation between percentile scores for the WJ-III Passage Comprehension subtest and the FA values in the right and left ILF and SLF indicated positive correlation in language-related ROIs, with greater distribution in the right hemisphere, which in turn showed strong connectivity in the fMRI data from the Sentence Picture Matching task. These results support the participation of the right hemisphere in reading comprehension and may provide physiologic support for a distinction between different types of reading comprehension deficits vs difficulties in technical reading.

Priming of Early Closure: Evidence for the Lexical Boost during Sentence Comprehension

Two self-paced reading experiments investigated priming in sentences containing "early" vs. "late closure" ambiguities. Early closure sentences impose relatively large processing costs at the point of syntactic disambiguation (Frazier & Rayner, 1982). The current study investigated a possible way to reduce processing costs. Target sentences were temporarily ambiguous and were disambiguated towards either the preferred "late" closure analysis or the dispreferred "early" closure analysis. Each target sentence was preceded by a prime that was either structurally identical or that required a different syntactic analysis. In Experiment 1, all of the prime sentences shared the same critical verb as the target (Arai et al., 2007; Carminati et al., 2008; Tooley et al., 2009, in press; Traxler et al., in press; Weber & Indefrey, 2009). In Experiment 2, verb repetition was eliminated by reorganizing the stimuli from Experiment 1. In Experiment 1, processing of the disambiguating verb was facilitated when an "early" closure target sentence followed an "early" closure prime. In Experiment 2, there were no significant priming effects, although an overall difference in processing time favored "late closure" targets. Combined analyses verified that the pattern of results in Experiment 1 differed significantly from Experiment 2. These experiments provide the first indication that "early" closure analyses can be primed and that such priming is more robust when a critical verb appears in both the prime and the target sentence. The results add to the body of data indicating a "lexical boost" for syntactic priming effects during comprehension. They have implications for theories of syntactic representation and processing (e.g., Boland & Blodgett, 2006; Vosse & Kempen, 2009; Sag et al., 2003).

Involvement of the right hemisphere in reading comprehension: a DTI study

The Simple View of reading emphasizes the critical role of two factors in normal reading skills: word recognition and reading comprehension. The current study aims to identify the anatomical support for aspects of reading performance that fall within these two components. Fractional anisotropy (FA) values were obtained from diffusion tensor images in twenty-one typical adolescents and young adults using the tract based spatial statistics (TBSS) method. We focused on the arcuate fasciculus (AF) and inferior longitudinal fasciculus (ILF) as fiber tracts that connect regions already implicated in the distributed cortical network for reading. Our results demonstrate dissociation between word-level and narrative-level reading skills: the FA values for both left and right ILF were correlated with measures of word reading, while only the left ILF correlated with reading comprehension scores. FA in the AF, however, correlated only with reading comprehension scores, bilaterally. Correlations with the right AF were particularly robust, emphasizing the contribution of the right hemisphere, especially the frontal lobe, to reading comprehension performance on the particular passage comprehension test used in this study. The anatomical dissociation between these reading skills is supported by the Simple View theory and may shed light on why these two skills dissociate in those with reading disorders.

Understanding mechanisms in transitive inferences: an eye-tracking study in Korean reading

The current experiment examined the mechanism of relational information processing by assessing transitive inferences in different syntactic structures. More specifically, the current experiment focused on whether the demands of conscious inference processing interact with the difficulty of syntactic processing. This research used the eye-tracking method to investigate online processing mechanisms in complex sentences with transitive inference. Overall sentence reading times, accuracy rates of comprehension questions, and the two eye-movement measures of gaze duration and re-reading times were examined in 32 participants. The results showed that inference processing demands affected overall reading times and accuracy rates, while syntactic processing demands did not have an effect on overall reading times or accuracy rates. The results of the eye-tracking measures showed that syntactic processing demands affected gaze duration, while the inference processing demand affected re-reading times. Apparently, the difficulty of inference processing was not affected by the surface form of a sentence. The results of this study suggested that basic processes of sentence interpretation share resources with other cognitive processes such as inference.

Processing Chinese relative clauses: evidence for the subject-relative advantage

A general fact about language is that subject relative clauses are easier to process than object relative clauses. Recently, several self-paced reading studies have presented surprising evidence that object relatives in Chinese are easier to process than subject relatives. We carried out three self-paced reading experiments that attempted to replicate these results. Two of our three studies found a subject-relative preference, and the third study found an object-relative advantage. Using a random effects bayesian meta-analysis of fifteen studies (including our own), we show that the overall current evidence for the subject-relative advantage is quite strong (approximate posterior probability of a subject-relative advantage given the data: 78-80%). We argue that retrieval/integration based accounts would have difficulty explaining all three experimental results. These findings are important because they narrow the theoretical space by limiting the role of an important class of explanation-retrieval/integration cost-at least for relative clause processing in Chinese.

The role of animacy in Chinese relative clause processing

Two experiments investigated Chinese relative clause processing by manipulating the animacy of the head noun phrases in the matrix clause (hereafter called head NPs) and in the embedded clause (hereafter called relative-clause-internal NPs) in a self-paced reading paradigm. Experiment 1 showed that subject-modifying object relative clauses (S-ORCs) were easier to process than subject-modifying subject relative clauses (S-SRCs) under animate-inanimate configuration (animate relative-clause-internal NPs and inanimate head NPs), but S-SRCs were easier to process than S-ORCs under inanimate-animate configuration (inanimate relative-clause-internal NPs and animate head NPs). Experiment 2 showed that object-modifying object relative clauses (O-ORCs) were easier to process than object-modifying subject relative clauses (O-SRCs) under both animacy configurations. These results suggest that animacy configuration of the relative-clause-internal NPs and the head NPs plays an important role in Chinese relative clause processing. These results can be explained by thematic fit accounts.

Subject/object processing asymmetries in Korean relative clauses: Evidence from ERP data

Subject relative (SR) clauses have a reliable processing advantage in VO languages like English in which relative clauses (RCs) follow the head noun. The question is whether this is also routinely true of OV languages like Japanese and Korean, in which RCs precede the head noun. We conducted an event-related brain potential (ERP) study of Korean RCs to test whether the SR advantage manifests in brain responses as well, and to tease apart the typological factors that might contribute to them. Our results suggest that brain responses to RCs are remarkably similar in VO and OV languages, but that ordering of the RC and its head noun localizes the response to different sentence positions. Our results also suggest that marking the right edge of the RC in Chinese (Yang et al. 2010) and Korean and the absence of it in Japanese (Ueno & Garnsey 2008) affect the response to the following head noun. The consistent SR advantage found in ERP studies lends further support to a universal subject preference in the processing of relative clauses.

How age of bilingual exposure can change the neural systems for language in the developing brain: a functional near infrared spectroscopy investigation of syntactic processing in monolingual and bilingual children

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Early life bilingual language experience can change the developing brain.

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Age of first bilingual exposure predicts neural activation for language.

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Bilinguals show greater extent and variability of neural activity in language areas.

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Early-exposed bilinguals show greater activation in IFG and STG vs. monolinguals.

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Later-exposed bilinguals have greater DLPFC activity vs. early bilinguals.

Is the developing bilingual brain fundamentally similar to the monolingual brain (e.g., neural resources supporting language and cognition)? Or, does early-life bilingual language experience change the brain? If so, how does age of first bilingual exposure impact neural activation for language?

We compared how typically-developing bilingual and monolingual children (ages 7–10) and adults recruit brain areas during sentence processing using functional Near Infrared Spectroscopy (fNIRS) brain imaging. Bilingual participants included early-exposed (bilingual exposure from birth) and later-exposed individuals (bilingual exposure between ages 4–6).

Both bilingual children and adults showed greater neural activation in left-hemisphere classic language areas, and additionally, right-hemisphere homologues (Right Superior Temporal Gyrus, Right Inferior Frontal Gyrus). However, important differences were observed between early-exposed and later-exposed bilinguals in their earliest-exposed language. Early bilingual exposure imparts fundamental changes to classic language areas instead of alterations to brain regions governing higher cognitive executive functions. However, age of first bilingual exposure does matter. Later-exposed bilinguals showed greater recruitment of the prefrontal cortex relative to early-exposed bilinguals and monolinguals.

The findings provide fascinating insight into the neural resources that facilitate bilingual language use and are discussed in terms of how early-life language experiences can modify the neural systems underlying human language processing.

Neurobiological bases of reading comprehension: Insights from neuroimaging studies of word level and text level processing in skilled and impaired readers

For accurate reading comprehension, readers must first learn to map letters to their corresponding speech sounds and meaning and then they must string the meanings of many words together to form a representation of the text. Furthermore, readers must master the complexities involved in parsing the relevant syntactic and pragmatic information necessary for accurate interpretation. Failure in this process can occur at multiple levels and cognitive neuroscience has been helpful in identifying the underlying causes of success and failure in reading single words and in reading comprehension. In general, neurobiological studies of skilled reading comprehension indicate a highly overlapping language circuit for single word reading, reading comprehension and listening comprehension with largely quantitative differences in a number of reading and language related areas. This paper reviews relevant research from studies employing neuroimaging techniques to study reading with a focus on the relationship between reading skill, single word reading, and text comprehension.

Mechanism of case processing in the brain: an fMRI study

In sentence comprehension research, the case system, which is one of the subsystems of the language processing system, has been assumed to play a crucial role in signifying relationships in sentences between noun phrases (NPs) and other elements, such as verbs, prepositions, nouns, and tense. However, so far, less attention has been paid to the question of how cases are processed in our brain. To this end, the current study used fMRI and scanned the brain activity of 15 native English speakers during an English-case processing task. The results showed that, while the processing of all cases activates the left inferior frontal gyrus and posterior part of the middle temporal gyrus, genitive case processing activates these two regions more than nominative and accusative case processing. Since the effect of the difference in behavioral performance among these three cases is excluded from brain activation data, the observed different brain activations would be due to the different processing patterns among the cases, indicating that cases are processed differently in our brains. The different brain activations between genitive case processing and nominative/accusative case processing may be due to the difference in structural complexity between them.

Syntactic structure building in the anterior temporal lobe during natural story listening

The neural basis of syntax is a matter of substantial debate. In particular, the inferior frontal gyrus (IFG), or Broca's area, has been prominently linked to syntactic processing, but the anterior temporal lobe has been reported to be activated instead of IFG when manipulating the presence of syntactic structure. These findings are difficult to reconcile because they rely on different laboratory tasks which tap into distinct computations, and may only indirectly relate to natural sentence processing. Here we assessed neural correlates of syntactic structure building in natural language comprehension, free from artificial task demands. Subjects passively listened to Alice in Wonderland during functional magnetic resonance imaging and we correlated brain activity with a word-by-word measure of the amount syntactic structure analyzed. Syntactic structure building correlated with activity in the left anterior temporal lobe, but there was no evidence for a correlation between syntactic structure building and activity in inferior frontal areas. Our results suggest that the anterior temporal lobe computes syntactic structure under natural conditions.

Broca's area and sentence comprehension: a relationship parasitic on dependency, displacement or predictability?

The current rapid event-related fMRI study used optional parasitic-gap constructions, such as [Which paper] did the tired student submit [(gap)--] after reviewing [(p-gap)--/it]?, to test 3 potential roles for Broca's area in sentence processing. These 3 functional options are: I. any intra-sentential Dependency relation activates Broca's area. II. This region specifically processes syntactic Displacement or movement. III. Broca's area handles any dependency relation, as long as it is predictable at an early stage of processing. Broca's area was only activated by the contrast that tested predictability within BA 45, as determined by its overlap with cytoarchitectonic probability maps. These results imply that an alternative or modified functional account of Broca's area, from those presently available, is required. Constraints on either a displacement account to movements that are not parasitic or a Working Memory one to predicted dependencies that cross verbal arguments or noun phrases would achieve the necessary consistency. Further, the results from the minimal contrasts investigating displacement and dependency have implications to potential language regions outside of Broca's area. The minimal contrast investigating displacement activated the left anterior Middle Temporal Gyrus, which has more recently been claimed to play a role in syntactic operations.

The brain basis of language processing: from structure to function

Language processing is a trait of human species. The knowledge about its neurobiological basis has been increased considerably over the past decades. Different brain regions in the left and right hemisphere have been identified to support particular language functions. Networks involving the temporal cortex and the inferior frontal cortex with a clear left lateralization were shown to support syntactic processes, whereas less lateralized temporo-frontal networks subserve semantic processes. These networks have been substantiated both by functional as well as by structural connectivity data. Electrophysiological measures indicate that within these networks syntactic processes of local structure building precede the assignment of grammatical and semantic relations in a sentence. Suprasegmental prosodic information overtly available in the acoustic language input is processed predominantly in a temporo-frontal network in the right hemisphere associated with a clear electrophysiological marker. Studies with patients suffering from lesions in the corpus callosum reveal that the posterior portion of this structure plays a crucial role in the interaction of syntactic and prosodic information during language processing.

The neural basis of reversible sentence comprehension: evidence from voxel-based lesion symptom mapping in aphasia

We explored the neural basis of reversible sentence comprehension in a large group of aphasic patients (n = 79). Voxel-based lesion symptom mapping revealed a significant association between damage in temporo-parietal cortex and impaired sentence comprehension. This association remained after we controlled for phonological working memory. We hypothesize that this region plays an important role in the thematic or what-where processing of sentences. In contrast, we detected weak or no association between reversible sentence comprehension and the ventrolateral pFC, which includes Broca's area, even for syntactically complex sentences. This casts doubt on theories that presuppose a critical role for this region in syntactic computations.

Network modulation during complex syntactic processing

Complex sentence processing is supported by a left-lateralized neural network including inferior frontal cortex and posterior superior temporal cortex. This study investigates the pattern of connectivity and information flow within this network. We used fMRI BOLD data derived from 12 healthy participants reported in an earlier study (Thompson, C. K., Den Ouden, D. B., Bonakdarpour, B., Garibaldi, K., & Parrish, T. B. (2010b). Neural plasticity and treatment-induced recovery of sentence processing in agrammatism. Neuropsychologia, 48(11), 3211-3227) to identify activation peaks associated with object-cleft over syntactically less complex subject-cleft processing. Directed Partial Correlation Analysis was conducted on time series extracted from participant-specific activation peaks and showed evidence of functional connectivity between four regions, linearly between premotor cortex, inferior frontal gyrus, posterior superior temporal sulcus and anterior middle temporal gyrus. This pattern served as the basis for Dynamic Causal Modeling of networks with a driving input to posterior superior temporal cortex, which likely supports thematic role assignment, and networks with a driving input to inferior frontal cortex, a core region associated with syntactic computation. The optimal model was determined through both frequentist and Bayesian Model Selection and turned out to reflect a network with a primary drive from inferior frontal cortex and modulation of the connection between inferior frontal cortex and posterior superior temporal cortex by complex sentence processing. The winning model also showed a substantive role for a feedback mechanism from posterior superior temporal cortex back to inferior frontal cortex. We suggest that complex syntactic processing is driven by word-order analysis, supported by inferior frontal cortex, in an interactive relation with posterior superior temporal cortex, which supports verb argument structure processing.

How the ventral pathway got lost: and what its recovery might mean

Textbooks dealing with the anatomical representation of language in the human brain display two language-related zones, Broca's area and Wernicke's area, connected by a single dorsal fiber tract, the arcuate fascicle. This classical model is incomplete. Modern imaging techniques have identified a second long association tract between the temporal and prefrontal language zones, taking a ventral course along the extreme capsule. This newly identified ventral tract connects brain regions needed for language comprehension, while the well-known arcuate fascicle is used for "sensorimotor mapping" during speech production. More than 130 years ago, Carl Wernicke already described a ventral connection for language, almost identical to the present results, but during scientific debate in the following decades either its function or its existence were rejected. This article tells the story of how this knowledge was lost and how the ventral connection, and in consequence the dual system, fits into current hypotheses and how language relates to other systems.

Proficiency differences in syntactic processing of monolingual native speakers indexed by event-related potentials

Although anecdotally there appear to be differences in the way native speakers use and comprehend their native language, most empirical investigations of language processing study university students and none have studied differences in language proficiency, which may be independent of resource limitations such as working memory span. We examined differences in language proficiency in adult monolingual native speakers of English using an ERP paradigm. ERPs were recorded to insertion phrase structure violations in naturally spoken English sentences. Participants recruited from a wide spectrum of society were given standardized measures of English language proficiency, and two complementary ERP analyses were performed. In between-groups analyses, participants were divided on the basis of standardized proficiency scores into lower proficiency and higher proficiency groups. Compared with lower proficiency participants, higher proficiency participants showed an early anterior negativity that was more focal, both spatially and temporally, and a larger and more widely distributed positivity (P600) to violations. In correlational analyses, we used a wide spectrum of proficiency scores to examine the degree to which individual proficiency scores correlated with individual neural responses to syntactic violations in regions and time windows identified in the between-groups analyses. This approach also used partial correlation analyses to control for possible confounding variables. These analyses provided evidence for the effects of proficiency that converged with the between-groups analyses. These results suggest that adult monolingual native speakers of English who vary in language proficiency differ in the recruitment of syntactic processes that are hypothesized to be at least in part automatic as well as of those thought to be more controlled. These results also suggest that to fully characterize neural organization for language in native speakers it is necessary to include participants of varying proficiency.

Neural plasticity and treatment-induced recovery of sentence processing in agrammatism

This study examined patterns of neural activation associated with treatment-induced improvement of complex sentence production (and comprehension) in six individuals with stroke-induced agrammatic aphasia, taking into account possible alterations in blood flow often associated with stroke, including delayed time-to-peak of the hemodynamic response function (HRF) and hypoperfused tissue. Aphasic participants performed an auditory verification fMRI task, processing object cleft, subject cleft, and simple active sentences, prior to and following a course of Treatment of Underlying Forms (TUF; Thompson et al., 2003), a linguistically based approach for treating aphasic sentence deficits, which targeted object relative clause constructions. The patients also were scanned in a long-trials task to examine HRFs, to account for any local deviations resulting from stroke, and perfusion images were obtained to evaluate regions of hypoperfused tissue. Region-of-interest (ROI) analyses were conducted (bilaterally), modeling participant-specific local HRFs in left hemisphere areas activated by 12 healthy age-matched volunteers performing the same task, including the middle and inferior frontal gyri, precentral gyrus, middle and superior temporal gyri, and insula, and additional regions associated with complex syntactic processing, including the posterior perisylvian and superior parietal cortices. Results showed that, despite individual variation in activation differences from pre- to post-treatment scans in the aphasic participants, main-effects analyses revealed a general shift from left superior temporal activation to more posterior temporoparietal areas, bilaterally. Time-to-peak of these responses correlated negatively with blood flow, as measured with perfusion imaging.

The picture of the linguistic brain: how sharp can it be? Reply to Fedorenko & Kanwisher

What is the best way to learn how the brain analyzes linguistic input? Two popular methods have attempted to segregate and localize linguistic processes: analyses of language deficits subsequent to (mostly focal) brain disease, and functional Magnetic Resonance Imaging (fMRI) in health. A recent Compass article by Fedorenko and Kanwisher (FK, 2009) observes that these methods group together data from many individuals through methods that rely on variable anatomical landmarks, and that results in a murky picture of how language is represented in the brain. To get around the variability problem, FK propose to import into neurolinguistics a method that has been successfully used in vision research - one that locates functional Regions Of Interest (fROIs) in each individual brain.In this note, I propose an alternative perspective. I first take issue with FK's reading of the literature. I point out that, when the neurolinguistic landscape is examined with the right linguistic spectacles, the emerging picture - while intriguingly complex - is not murky, but rather, stable and clear, parsing the linguistic brain into functionally and anatomically coherent pieces. I then examine the potential value of the method that FK propose, in light of important micro-anatomical differences between language and high-level vision areas, and conclude that as things stand the method they propose is not very likely to bear much fruit in neurolinguistic research.

Individual differences in auditory sentence comprehension in children: An exploratory event-related functional magnetic resonance imaging investigation

The purpose of this study was to explore changes in activation of the cortical network that serves auditory sentence comprehension in children in response to increasing demands of complex sentences. A further goal is to study how individual differences in children's receptive language abilities are associated with such changes in cortical responses. Fourteen children, 10-16 years old, participated in an event-related functional magnetic resonance imaging experiment using a cross modal sentence-picture verification paradigm. We manipulated sentence difficulty and length in a 2x2 factorial design. Task-related activation covered large regions of the left and right superior temporal cortex, inferior parietal lobe, precuneous, cingulate, middle frontal gyrus and precentral gyrus. Sentence difficulty, independent of length, led to increased activation in the left temporal-parietal junction and right superior temporal gyrus. Changes in activation in frontal regions positively correlated with age-standardized receptive vocabulary scores and negatively correlated with reaction time on a receptive grammar test outside the scanner. Thus, individual differences in language skills were associated with changes in the network in response to changing task demands. These preliminary findings in a small sample of typically developing children suggest that the investigation of individual differences may prove useful in elucidating the underlying neural mechanisms of language disorders in children.

Task effects on BOLD signal correlates of implicit syntactic processing

BOLD signal was measured in sixteen participants who made timed font change detection judgments in visually presented sentences that varied in syntactic structure and the order of animate and inanimate nouns. Behavioral data indicated that sentences were processed to the level of syntactic structure. BOLD signal increased in visual association areas bilaterally and left supramarginal gyrus in the contrast of sentences with object- and subject-extracted relative clauses without font changes in which the animacy order of the nouns biased against the syntactically determined meaning of the sentence. This result differs from the findings in a non-word detection task (Caplan et al, 2008a), in which the same contrast led to increased BOLD signal in the left inferior frontal gyrus. The difference in areas of activation indicates that the sentences were processed differently in the two tasks. These differences were further explored in an eye tracking study using the materials in the two tasks. Issues pertaining to how parsing and interpretive operations are affected by a task that is being performed, and how this might affect BOLD signal correlates of syntactic contrasts, are discussed.

Neuronal activation for semantically reversible sentences

Semantically reversible sentences are prone to misinterpretation and take longer for typically developing children and adults to comprehend; they are also particularly problematic for those with language difficulties such as aphasia or Specific Language Impairment. In our study, we used fMRI to compare the processing of semantically reversible and nonreversible sentences in 41 healthy participants to identify how semantic reversibility influences neuronal activation. By including several linguistic and nonlinguistic conditions within our paradigm, we were also able to test whether the processing of semantically reversible sentences places additional load on sentence-specific processing, such as syntactic processing and syntactic-semantic integration, or on phonological working memory. Our results identified increased activation for reversible sentences in a region on the left temporal-parietal boundary, which was also activated when the same group of participants carried out an articulation task which involved saying "one, three" repeatedly. We conclude that the processing of semantically reversible sentences places additional demands on the subarticulation component of phonological working memory.

The effect of semantic relatedness on syntactic analysis: An fMRI study

The sentences we process in normal conversation tend to refer to information that we are familiar with rather than abstract, unrelated information. This allows for the use of knowledge stores to help facilitate comprehension processes. In many sentence comprehension studies, the stimuli are designed such that the use of world knowledge is limited. Here, we investigated how the semantic relatedness of sentence constituents influences sentence processing. A three factor design was employed in which processing phase (sentence vs. probe), syntactic complexity (object-relative vs. conjoined active) and the semantic relatedness of the nouns within the sentence was examined. We found a differential effect in two sub-regions of the left inferior frontal gyrus (LIFG). BA 44 revealed an effect of syntactic complexity while inferior portions of the LIFG (BA 47) revealed an effect of relatedness as well as an interaction between complexity and relatedness during the probe phase. In addition, significant differences in activation were observed when comparing the sentence processing and probe phases with the sentence phase eliciting stronger semantic related activation while the probe phase elicited stronger working memory related activation.

Active perception: sensorimotor circuits as a cortical basis for language

Action and perception are functionally linked in the brain, but a hotly debated question is whether perception and comprehension of stimuli depend on motor circuits. Brain language mechanisms are ideal for addressing this question. Neuroimaging investigations have found specific motor activations when subjects understand speech sounds, word meanings and sentence structures. Moreover, studies involving transcranial magnetic stimulation and patients with lesions affecting inferior frontal regions of the brain have shown contributions of motor circuits to the comprehension of phonemes, semantic categories and grammar. These data show that language comprehension benefits from frontocentral action systems, indicating that action and perception circuits are interdependent.

Brain embodiment of syntax and grammar: discrete combinatorial mechanisms spelt out in neuronal circuits

Neuroscience has greatly improved our understanding of the brain basis of abstract lexical and semantic processes. The neuronal devices underlying words and concepts are distributed neuronal assemblies reaching into sensory and motor systems of the cortex and, at the cognitive level, information binding in such widely dispersed circuits is mirrored by the sensorimotor grounding of form and meaning of symbols. Recent years have seen the emergence of evidence for similar brain embodiment of syntax. Neurophysiological studies have accumulated support for the linguistic notion of abstract combinatorial rules manifest as functionally discrete neuronal assemblies. Concepts immanent to the theory of abstract automata could be grounded in observations from modern neuroscience, so that it became possible to model abstract pushdown storage - which is critical for building linguistic tree structure representations - as ordered dynamics of memory circuits in the brain. At the same time, neurocomputational research showed how sequence detectors already known from animal brains can be neuronally linked so that they merge into larger functionally discrete units, thereby underpinning abstract rule representations that syntactically bind lexicosemantic classes of morphemes and words into larger meaningful constituents. Specific predictions of brain-based grammar models could be confirmed by neurophysiological and brain imaging experiments using MEG, EEG and fMRI. Neuroscience and neurocomputational research offering perspectives on understanding abstract linguistic mechanisms in terms of neuronal circuits and their interactions therefore point programmatic new ways to future theory-guided experimental investigation of the brain basis of grammar.

Greater leftward lateralization of the inferior frontal gyrus in second language learners with higher syntactic abilities

There is a great individual variability for acquiring syntactic knowledge in a second language (L2). Little is, however, known if there is any anatomical basis in the brain for individual differences in syntactic acquisition. Here we examined brain structures in 95 nonnative speakers of English, including 78 high-school students and 17 adult international students. We found a significant correlation between the performance of a syntactic task and leftward lateralization of a single region in the triangular part (F3t) of the inferior frontal gyrus, which has been proposed as the grammar center. Moreover, this correlation was independent of the performance of a spelling task, age, gender, and handedness. This striking result suggests that the neural basis for syntactic abilities in L2 is independent of that for lexical knowledge in L2, further indicating that the individual differences in syntactic acquisition are related to the lateralization of the grammar center.

The effect of presentation paradigm on syntactic processing: An event-related fMRI study

An event-related fMRI study was conducted to investigate the effect of two different sentence presentation paradigms-rapid serial visual presentation (RSVP) and whole sentence presentation-on syntactic processing. During scanning, sentences were presented using one of the two presentation paradigms and were followed by a short delay and a probe to verify sentence comprehension. The delay was included in an attempt to separate sentence-related activity from probe-related activity. The behavioral data showed a main effect of syntactic complexity for reaction time and accuracy, and accuracy revealed an interaction between complexity and the presentation paradigm employed-RSVP produced many more errors for syntactically complex sentences than did whole sentence presentation. The imaging data revealed a syntactic complexity effect during the sentence phase in left BA 44 and during the probe phase in left BA 44 and the left posterior MTG. In addition, timecourse analysis revealed that these two regions also showed an interaction between complexity and presentation paradigm such that there was no complexity effect during RSVP but a significant effect during whole sentence presentation. In addition to finding that these two presentation paradigms differentially affected syntactic processing, there were main effects within the visual pathway (V1/V2 vs. V5) and the hippocampus that revealed significant differences in activation between the paradigms.

Subject relative clauses are not universally easier to process: Evidence from Basque

Studies from many languages consistently report that subject relative clauses (SR) are easier to process than object relatives (OR). However, Hsiao and Gibson (2003) report an OR preference for Chinese, a finding that has been contested. Here we report faster OR versus SR processing in Basque, an ergative, head-final language with pre-nominal relative clauses. A self-paced reading task was used in Experiments 1 and 2, while ERPs were recorded in Experiment 3. We used relative clauses that were ambiguous between an object or subject-gap interpretation and disambiguated later in the sentence. The results of Experiments 1 and 2 showed that SR took longer to read than OR in the critical disambiguating region. In addition, Experiment 3 showed that SR produced larger amplitudes than OR in the P600 window immediately after reading the critical disambiguating word. Our results suggest that SR are not universally easier to process. They cast doubts on universal hypotheses and suggest that processing complexity may depend on language-specific aspects of grammar.