From minimal dependencies to sentence contexts: neural correlates of agreement processing

289 p.Language comprehension is incremental, involving the integration of formal and conceptual information from different words, together with the need to resolve conflicting cues when unexpected information occurs. However, despite the extensive amount of findings regarding how the brain deals with these information, two essential and still open questions are 1whether the neural circuit(s) for coding syntactic and semantic information embedded in our linguistic code are the same or different, and 2whether the possible interaction(s) between these two different types of information leaves a trace in the brain response. The current thesis seeks to segregate the neuro-anatomical substrates of these processes by taking advantage of the Spanish agreement system. This system comprised those procedural mechanisms concerning the regular assignment of the number [singular, plural], person [first, second and third] and/or gender [feminine, masculine] information, associated with different sentence constituents. Experimental manipulations concerning different agreement features and the elements involved in an agreement relation, allowed us to characterize the neural network underlying agreement processing. This thesis comprised five experiments: while experiments I and II explored nominal dependencies in local as well as non-local relations, experiments III, IV and V explored subject-verb relations in a more complex sentence context. To distinguish between purely syntactic mechanisms and those where semantic and syntactic factors would interact during language comprehension, different types of agreement relations and/or agreement features were manipulated in well- and ill-formed constructions. The interaction effect between the different factors included in each experiment was always the critical comparison. In general, our results include firstly a functional dissociation between well-formed and ill-formed constructions: while ill-formed constructions recruited a bilateral distributed fronto-parietal network associated to conflict monitoring operations, not language specific, well-formed constructions recruited a left lateralized fronto-temporo-parietal network that seems to be specifically related to different aspects of phrase and sentence processing. Secondly, there was an anterior to posterior functional gradient associated to the middle and superior temporal cortex that consistently appears across experiments. Specifically, while the posterior portion of the left MTG-STG seems to be related to the storage and retrieval of lexical and morpho-syntactic information, the anterior portion of this region was related to syntactic-combinatorial building mechanisms. Critically, in the most anterior part of the left temporal cortex, corresponding with the middle and superior temporal pole, form-to-meaning mapping processes seems to be represented. Thirdly, the response of the left temporal cortex appears to be controlled by left inferior frontal regions (LIFG). Finally, left parietal regions such us the angular gyrus showed increased activation for those manipulations involving semantic factors (e.g., conceptual gender and Unagreement constructions), highlighting its crucial role in the processing of different types of semantic information (e.g., conceptual integration and semantic-discourse integration). Overall, these findings highlight the sensitivity of the agreement system to syntactic and semantic factors embedded into an agreement relation, opening new windows to the study of agreement computation and language comprehension.bcbl: basque center on cognition, brain and languag

From minimal dependencies to sentence contexts: neural correlates of agreement processing

289 p.Language comprehension is incremental, involving the integration of formal and conceptual information from different words, together with the need to resolve conflicting cues when unexpected information occurs. However, despite the extensive amount of findings regarding how the brain deals with these information, two essential and still open questions are 1whether the neural circuit(s) for coding syntactic and semantic information embedded in our linguistic code are the same or different, and 2whether the possible interaction(s) between these two different types of information leaves a trace in the brain response. The current thesis seeks to segregate the neuro-anatomical substrates of these processes by taking advantage of the Spanish agreement system. This system comprised those procedural mechanisms concerning the regular assignment of the number [singular, plural], person [first, second and third] and/or gender [feminine, masculine] information, associated with different sentence constituents. Experimental manipulations concerning different agreement features and the elements involved in an agreement relation, allowed us to characterize the neural network underlying agreement processing. This thesis comprised five experiments: while experiments I and II explored nominal dependencies in local as well as non-local relations, experiments III, IV and V explored subject-verb relations in a more complex sentence context. To distinguish between purely syntactic mechanisms and those where semantic and syntactic factors would interact during language comprehension, different types of agreement relations and/or agreement features were manipulated in well- and ill-formed constructions. The interaction effect between the different factors included in each experiment was always the critical comparison. In general, our results include firstly a functional dissociation between well-formed and ill-formed constructions: while ill-formed constructions recruited a bilateral distributed fronto-parietal network associated to conflict monitoring operations, not language specific, well-formed constructions recruited a left lateralized fronto-temporo-parietal network that seems to be specifically related to different aspects of phrase and sentence processing. Secondly, there was an anterior to posterior functional gradient associated to the middle and superior temporal cortex that consistently appears across experiments. Specifically, while the posterior portion of the left MTG-STG seems to be related to the storage and retrieval of lexical and morpho-syntactic information, the anterior portion of this region was related to syntactic-combinatorial building mechanisms. Critically, in the most anterior part of the left temporal cortex, corresponding with the middle and superior temporal pole, form-to-meaning mapping processes seems to be represented. Thirdly, the response of the left temporal cortex appears to be controlled by left inferior frontal regions (LIFG). Finally, left parietal regions such us the angular gyrus showed increased activation for those manipulations involving semantic factors (e.g., conceptual gender and Unagreement constructions), highlighting its crucial role in the processing of different types of semantic information (e.g., conceptual integration and semantic-discourse integration). Overall, these findings highlight the sensitivity of the agreement system to syntactic and semantic factors embedded into an agreement relation, opening new windows to the study of agreement computation and language comprehension.bcbl: basque center on cognition, brain and languag

An fMRI study of grammatical morpheme processing associated with nouns and verbs in Chinese

This study examined whether the degree of complexity of a grammatical component in a language would impact on its representation in the brain through identifying the neural correlates of grammatical morpheme processing associated with nouns and verbs in Chinese. In particular, the processing of Chinese nominal classifiers and verbal aspect markers were investigated in a sentence completion task and a grammaticality judgment task to look for converging evidence. The Chinese language constitutes a special case because it has no inflectional morphology per se and a larger classifier than aspect marker inventory, contrary to the pattern of greater verbal than nominal paradigmatic complexity in most European languages. The functional imaging results showed BA47 and left supplementary motor area and superior medial frontal gyrus more strongly activated for classifier processing, and the left posterior middle temporal gyrus more responsive to aspect marker processing. We attributed the activation in the left prefrontal cortex to greater processing complexity during classifier selection, analogous to the accounts put forth for European languages, and the left posterior middle temporal gyrus to more demanding verb semantic processing. The overall findings significantly contribute to cross-linguistic observations of neural substrates underlying processing of grammatical morphemes from an analytic and a classifier language, and thereby deepen our understanding of neurobiology of human language.published_or_final_versio

Contributions of memory circuits to language: The declarative/procedural model

The structure of the brain and the nature of evolution suggest that, despite its uniqueness, language likely depends on brain systems that also subserve other functions. The declarative/procedural (DP) model claims that the mental lexicon of memorized word-specific knowledge depends on the largely temporal-lobe substrates of declarative memory, which underlies the storage and use of knowledge of facts and events. The mental grammar, which subserves the rule-governed combination of lexical items into complex representations, depends on a distinct neural system. This system, which is composed of a network of specific frontal, basal-ganglia, parietal and cerebellar structures, underlies procedural memory, which supports the learning and execution of motor and cognitive skills, especially those involving sequences. The functions of the two brain systems, together with their anatomical, physiological and biochemical substrates, lead to specific claims and predictions regarding their roles in language. These predictions are compared with those of other neurocognitive models of language. Empirical evidence is presented from neuroimaging studies of normal language processing, and from developmental and adult-onset disorders. It is argued that this evidence supports the DP model. It is additionally proposed that "language" disorders, such as specific language impairment and non-fluent and fluent aphasia, may be profitably viewed as impairments primarily affecting one or the other brain system. Overall, the data suggest a new neurocognitive framework for the study of lexicon and grammar

Neural connectivity in syntactic movement processing

Linguistic theory suggests non-canonical sentences subvert the dominant agent-verb-theme order in English via displacement of sentence constituents to argument (NP-movement) or non-argument positions (wh-movement). Both processes have been associated with the left inferior frontal gyrus and posterior superior temporal gyrus, but differences in neural activity and connectivity between movement types have not been investigated. In the current study, functional magnetic resonance imaging data were acquired from 21 adult participants during an auditory sentence-picture verification task using passive and active sentences contrasted to isolate NP-movement, and object- and subject-cleft sentences contrasted to isolate wh-movement. Then, functional magnetic resonance imaging data from regions common to both movement types were entered into a dynamic causal modeling analysis to examine effective connectivity for wh-movement and NP-movement. Results showed greater left inferior frontal gyrus activation for Wh > NP-movement, but no activation for NP > Wh-movement. Both types of movement elicited activity in the opercular part of the left inferior frontal gyrus, left posterior superior temporal gyrus, and left medial superior frontal gyrus. The dynamic causal modeling analyses indicated that neither movement type significantly modulated the connection from the left inferior frontal gyrus to the left posterior superior temporal gyrus, nor vice-versa, suggesting no connectivity differences between wh- and NP-movement. These findings support the idea that increased complexity of wh-structures, compared to sentences with NP-movement, requires greater engagement of cognitive resources via increased neural activity in the left inferior frontal gyrus, but both movement types engage similar neural networks.This work was supported by the NIH-NIDCD, Clinical Research Center Grant, P50DC012283 (PI: CT), and the Graduate Research Grant and School of Communication Graduate Ignition Grant from Northwestern University (awarded to EE). (P50DC012283 - NIH-NIDCD, Clinical Research Center Grant; Graduate Research Grant and School of Communication Graduate Ignition Grant from Northwestern University)Published versio