Abstract linguistic structure correlates with temporal activity during naturalistic comprehension (original) (raw)
Related papers
Humans have a striking capacity to combine words into sentences that express new meanings. Previous research has identified key brain regions involved in this capacity, but little is known about the time course of activity in these regions, as hemodynamic methods such as fMRI provide little insight into temporal dynamics of neural activation. We performed an MEG experiment to elucidate the temporal dynamics of structure and content processing within four brain regions implicated by fMRI data from the same experiment: the temporo-parietal junction (TPJ), the posterior temporal lobe (PTL), the anterior temporal lobe (ATL), and the anterior inferior frontal gyrus (IFG). The TPJ showed increased activity for both structure and content near the end of the sentence, consistent with a role in incremental interpretation of event semantics. The PTL, a region not often associated with core aspects of syntax, showed a strong early effect of structure, consistent with predictive parsing models, and both structural and semantic context effects on function words. These results provide converging evidence that the PTL plays an important role in lexicalized syntactic processing. The ATL and IFG, regions traditionally associated with syntax, showed minimal effects of sentence structure. The ATL, PTL and IFG all showed effects of semantic content: increased activation for real words relative to nonwords. Our fMRI-guided MEG investigation therefore helps identify syntactic and semantic aspects of sentence comprehension in the brain in both spatial and temporal dimensions. K E Y W O R D S
Neural basis of processing sequential and hierarchical syntactic structures
Human Brain Mapping, 2007
The psychological processes through which humans learn a language have gained considerable interest over the past years. It has been previously suggested that language acquisition partly relies on a rule-based mechanism that is mediated by the frontal cortex. Interestingly, the actual structure involved within the frontal cortex varies with the kind of rules being processed. By means of functional MRI we investigated the neural underpinnings of rule-based language processing using an artificial language that allows direct comparisons between local phrase structure dependencies and hierarchically structured long-distance dependencies. Activation in the left ventral premotor cortex (PMC) was related to the local character of rule change, whereas long-distance dependencies activated the opercular part of the inferior frontal gyrus (Broca's area (BA) 44). These results suggest that the brain's involvement in syntactic processing is determined by the type of rule used, with BA 44/45 playing an important role during language processing when long-distance dependencies are processed. In contrast, the ventral PMC seems to subserve the processing of local dependencies. In addition, hippocampal activity was observed for local dependencies, indicating that the processing of such dependencies may be mediated by a second mechanism. Hum Brain Mapp 28: 585-592, 2007.
Disentangling Hierarchical and Sequential Computations during Sentence Processing
Sequence processing in humans is thought to rely on two distinct mechanisms: the computation of transition probabilities between adjacent elements and the extraction of larger hierarchical structures. Previous studies indicate that both mechanisms contribute to auditory sequence processing, but whether language processing involves one or the other remains debated. To address this issue, we designed a linguistic version of the local-global auditory test, which contrasts sequential versus hierarchical violations of expectations in sentences, and we searched for violation responses in both human magnetoencephalography and computational models. We found that in models, both mechanisms coexist, whereas humans only show hierarchical structure effects. Our results suggest that human sentence processing is dominated by structure-based computations and robust to sequential effects. They point to major differences between language processing in humans versus neural models and, within humans, ...
The neural basis of recursion of complex syntactic hierarchy
Biolinguistics, 2011
Language is a faculty specific to humans. It is characterized by hierarchical, recursive structures. The processing of hierarchically complex sentences is known to recruit Broca's area. Comparisons across brain imaging studies investigating similar hierarchical structures in different domains revealed that complex hierarchical structures that mimic those of natural languages mainly activate Broca's area, that is, left Brodmann area (BA) 44/45, whereas hierarchically structured mathematical formulae, moreover, strongly recruit more anteriorly located region BA 47. The present results call for a model of the prefrontal cortex assuming two systems of processing complex hierarchy: one system determined by cognitive control for which the posterior-toanterior gradient applies active in the case of processing hierarchically structured mathematical formulae, and one system which is confined to the posterior parts of the prefrontal cortex processing complex syntactic hierarchies in language efficiently.
Sentences encode hierarchical structural relations among words. Several neuroimaging experiments aiming to localize combinatory operations responsible for creating this structure during sentence comprehension have contrasted short, simple phrases and sentences to unstructured controls. Some of these experiments have revealed activation in the left inferior frontal gyrus (IFG) and posterior superior temporal sulcus (pSTS), associating these regions with basic syntactic combination. However, the wide variability of these effects across studies raises questions about this interpretation. In an fMRI experiment, we provide support for an alternative hypothesis: these regions underlie top-down syntactic predictions that facilitate sentence processing but are not necessary for building syntactic structure. We presented stimuli with three levels of structure: unstructured lists, two-word phrases, and simple, short sentences; and two levels of content: natural stimuli with real words and stimuli with open-class items replaced with pseudowords (jabberwocky). While both the phrase and sentence conditions engaged syntactic combination, our experiment only encouraged syntactic prediction in the sentence condition. We found increased activity for both natural and jabberwocky sentences in the left IFG (pars triangularis and pars orbitalis) and pSTS relative to unstructured word lists and two-word phrases, but we did not find any such effects for two-word phrases relative to unstructured word lists in these areas. Our results are most consistent with the hypothesis that increased activity in IFG and pSTS for basic contrasts of structure reflects syntactic prediction. The pars opercularis of the IFG showed a response profile consistent with verbal working memory. We found incremental effects of structure in the anterior temporal lobe (ATL), and increased activation only for sentences in the angular gyrus (AG)/temporaleparietal junction (TPJ) e both regions showed these effects for stimuli with all real words. These findings support a role for the ATL in semantic combination and the AG/TPJ in thematic processing.
Neurophysiological dynamics of phrase-structure building during sentence processing
Although sentences unfold sequentially, one word at a time, most linguistic theories propose that their underlying syntactic structure involves a tree of nested phrases rather than a linear sequence of words. Whether and how the brain builds such structures, however, remains largely unknown. Here, we used human intracranial recordings and visual word-byword presentation of sentences and word lists to investigate how left-hemispheric brain activity varies during the formation of phrase structures. In a broad set of language-related areas, comprising multiple superior temporal and inferior frontal sites, high-gamma power increased with each successive word in a sentence but decreased suddenly whenever words could be merged into a phrase. Regression analyses showed that each additional word or multiword phrase contributed a similar amount of additional brain activity, providing evidence for a merge operation that applies equally to linguistic objects of arbitrary complexity. More superficial models of language, based solely on sequential transition probability over lexical and syntactic categories, only captured activity in the posterior middle temporal gyrus. Formal model comparison indicated that the model of multiword phrase construction provided a better fit than probability-based models at most sites in superior temporal and inferior frontal cortices. Activity in those regions was consistent with a neural implementation of a bottom-up or left-corner parser of the incoming language stream. Our results provide initial intracranial evidence for the neurophysiological reality of the merge operation postulated by linguists and suggest that the brain compresses syntactically well-formed sequences of words into a hierarchy of nested phrases. intracranial | merge | constituent | neurolinguistics | open nodes
Human Brain Mapping, 2021
Grammar is central to any natural language. In the past decades, the artificial grammar of the AnBn type in which a pair of associated elements can be nested in the other pair was considered as a desirable model to mimic human language syntax without semantic interference. However, such a grammar relies on mere associating mechanisms, thus insufficient to reflect the hierarchical nature of human syntax. Here, we test how the brain imposes syntactic hierarchies according to the category relations on linearized sequences by designing a novel artificial “Hierarchical syntactic structure‐building Grammar” (HG), and compare this to the AnBn grammar as a “Nested associating Grammar” (NG) based on multilevel associations. Thirty‐six healthy German native speakers were randomly assigned to one of the two grammars. Both groups performed a grammaticality judgment task on auditorily presented word sequences generated by the corresponding grammar in the scanner after a successful explicit behav...
Processing Linguistic Complexity and Grammaticality in the Left Frontal Cortex
Cerebral Cortex, 2005
We used event-related functional magnetic resonance imaging to directly compare the hemodynamic responses associated with varying degrees of linguistic complexity with those engendered by the processing of ungrammatical utterances. We demonstrate a dissociation within the left inferior frontal cortex between the deep frontal operculum, which responds to syntactic violations, and a core region of Broca's area, that is, the inferior portion of the left pars opercularis in Brodmann area 44, the activation of which is modulated as a function of the complexity of well-formed sentences. The data demonstrate that different brain regions in the prefrontal cortex support distinct mechanisms in the mapping from a linguistic form onto meaning, thereby separating ungrammaticality from linguistic complexity.
The cortical organization of syntax
Cerebral Cortex
Syntax, the structure of sentences, enables humans to express an infinite range of meanings through finite means. The neurobiology of syntax has been intensely studied, but with little consensus. Two main candidate regions have been identified: the posterior inferior frontal gyrus (pIFG) and the posterior middle temporal gyrus (pMTG). Integrating research in linguistics, psycholinguistics, and neuroscience, we propose a neuroanatomical framework for syntax that attributes distinct syntactic computations to these regions in a unified model. The key theoretical advances are adopting a modern lexicalized view of syntax in which the lexicon and syntactic rules are intertwined, and recognizing a computational asymmetry in the role of syntax during comprehension and production. Our model postulates a hierarchical lexical-syntactic function to the pMTG, which interconnects previously identified speech perception and conceptual-semantic systems in the temporal and inferior parietal lobes, crucial for both sentence production and comprehension. These relational hierarchies are transformed via the pIFG into morpho-syntactic sequences, primarily tied to production. We show how this architecture provides a better account SYNTAX 2 of the full range of data and is consistent with recent proposals regarding the organization of phonological processes in the brain.