Grammaticality judgments on sentences with and without movement of phrasal constituents--An event-related fMRI study (original) (raw)
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Neural correlates of syntactic transformations
Human brain …, 2004
Many agrammatic aphasics have a specific syntactic comprehension deficit involving processing syntactic transformations. It has been proposed that this deficit is due to a dysfunction of Broca's area, an area that is thought to be critical for comprehension of complex transformed sentences. The goal of this study was to investigate the role of Broca's area in processing canonical and non-canonical sentences in healthy subjects. The sentences were presented auditorily and were controlled for task difficulty. Subjects were asked to judge the grammaticality of the sentences while their brain activity was monitored using event-related functional magnetic resonance imaging. Processing both kinds of sentences resulted in activation of language-related brain regions. Comparison of non-canonical and canonical sentences showed greater activation in bilateral temporal regions; a greater activation of Broca's area in processing antecedent-gap relations was not found. Moreover, the posterior part of Broca's area was conjointly activated by both sentence conditions. Broca's area is thus involved in general syntactic processing as required by grammaticality judgments and does not seem to have a specific role in processing syntactic transformations. Hum. Brain Mapp. 22:72 -81, 2004.
Sentence processing selectivity in Broca's area: evident for structure but not syntactic movement
Language, Cognition and Neuroscience, 2015
The role of Broca's area in sentence processing is hotly debated. Prominent hypotheses include that Broca's area supports sentence comprehension via syntax-specific processes ("syntactic movement" in particular), hierarchical structure building or working memory. In the present fMRI study we adopt a within subject, across task approach using targeted sentence-level contrasts and non-sentential comparison tasks to address these hypotheses regarding the role of Broca's area in sentence processing. For clarity, we have presented findings as three experiments: (i) Experiment 1 examines selectivity for a particular type of sentence construction, namely those containing syntactic movement. Standard syntactic movement distance effects in Broca's area were replicated but no difference was found between movement and non-movement sentences in Broca's area at the group level or consistently in individual subjects. (ii) Experiment 2 examines selectivity for sentences versus non-sentences, to assess claims regarding the role of Broca's area in hierarchical structure building. Group and individual results differ, but both identify subregions of Broca's area that are selective for sentence structure. (iii) Experiment 3 assesses whether activations in Broca's area are selective for sentences when contrasted with simple subvocal articulation. Group results suggest shared resources for sentence processing and articulation in Broca's area, but individual subject analyses contradict this finding. We conclude that Broca's area is not selectively involved in processing syntactic movement, but that subregions are selectively responsive to sentence structure. Our findings also reinforce Fedorenko & Kanwishser's call for the use of more individual subject analyses in functional imaging studies of sentence processing in Broca's area, as group findings can obscure selective response patterns.
Abstract Grammatical Processing of Nouns and Verbs in Broca's Area: Evidence from FMRI
Cortex, 2006
The role of Broca's area in grammatical computation is unclear, because syntactic processing is often confounded with working memory, articulation, or semantic selection. Morphological processing potentially circumvents these problems. Using event-related functional magnetic resonance imaging (fMRI), we had 18 subjects silently inflect words or read them verbatim. Subtracting the activity pattern for reading from that for inflection, which indexes processes involved in inflection (holding constant lexical processing and articulatory planning) highlighted left Brodmann area (BA) 44/45 (Broca's area), BA 47, anterior insula, and medial supplementary motor area. Subtracting activity during zero inflection (the hawk; they walk) from that during overt inflection (the hawks; they walked), which highlights manipulation of phonological content, implicated subsets of the regions engaged by inflection as a whole. Subtracting activity during verbatim reading from activity during zero inflection (which highlights the manipulation of inflectional features) implicated distinct regions of BA 44, 47, and a premotor region (thereby tying these regions to grammatical features), but failed to implicate the insula or BA 45 (thereby tying these to articulation). These patterns were largely similar in nouns and verbs and in regular and irregular forms, suggesting these regions implement inflectional features cutting across word classes. Greater activity was observed for irregular than regular verbs in the anterior cingulate and supplementary motor area (SMA), possibly reflecting the blocking of regular or competing irregular candidates. The results confirm a role for Broca's area in abstract grammatical processing, and are interpreted in terms of a network of regions in left prefrontal cortex (PFC) that are recruited for processing abstract morphosyntactic features and overt morphophonological content.
The brain circuitry of syntactic comprehension
Trends in Cognitive Sciences, 2002
Reading or hearing a sentence such as 'The little old man knocked out the giant wrestler' demonstrates the crucial role of syntax in normal language understanding. Identifying who did what to whom enables humans to understand the unlikely scenario that is described here. Thus, syntactic information helps us combine the words we hear or read in a particular way such that we can extract the meaning of sentences (see Box 1). Many regard syntax as a cognitive module that is separable from other more general cognitive processes such as memory and attention [1] and whose properties can be distinguished from semantic-conceptual information ('meaning') [2]. In this tradition, some theories of sentence processing propose a separate syntactic processing mechanism that is insensitive to nonsyntactic information [3]. However, alternative views exist [4,5]. Given these competing views of syntax, one can ask whether there is neurological evidence in favor of a syntactic processing module [1]; that is, is there a specific area in the brain that is specialized for syntax alone? Evidence from brain lesions Research on the relationship between brain and language dates back to the mid-to late-1800s when Paul Broca and Karl Wernicke linked specific lesions in the brain to specific language deficits known as aphasia. Broca identified patients with problems in Syntactic comprehension is a fundamental aspect of human language, and has distinct properties from other aspects of language (e.g. semantics). In this article, we aim to identify if there is a specific locus of syntax in the brain by reviewing imaging studies on syntactic processing. We conclude that results from neuroimaging support evidence from neuropsychology that syntactic processing does not recruit one specific area. Instead a network of areas including Broca's area and anterior, middle and superior areas of the temporal lobes is involved. However, none of these areas appears to be syntax specific.
This review chapter aims at presenting an overview of the seminal and the most recent behavioral and neuroimaging studies on the implementation of syntactic processes in the brain. More specifically, the present study seeks to provide an understanding of the most recent findings in relation to how syntactic processing takes place behaviorally and also concerning its cortical representation. Traditionally, syntactic processing has been investigated by comparing sentences with ambiguities and sentences without ambiguities; sentences with grammatical errors and sentences without grammatical errors; and sentences with more versus less complex syntactic structures. Different models have sought to explain how parsing occurs: serial models have posited that syntax is computed before word meanings while interactive models have suggested that syntax and semantics are computed simultaneously. Behavioral research has found evidence for both views. Lesion studies have led researchers to suggest that Broca’s area (left inferior frontal gyrus) would be responsible for syntax. With the advent of functional neuroimaging tools (as well as event-related potentials, ERPs) for language studies, researchers could examine the healthy brain at work. These tools have allowed research to go beyond the simple dissociations offered by lesion studies to study the organization of the brain. ERPs characterize the time course of a language process whereas fMRI (functional magnetic resonance imaging) and PET (positron-emission tomography) provide the necessary spatial resolution to determine the neural loci of language processing. These technological tools have challenged what we knew about syntactic processing, since they have been showing “the language system is organized into a large number of relatively small, but tightly clustered and interconnected modules with unique contributions to language processing” (BOOKHEIMER, 2002, p.152). The studies reviewed in the chapter are all consistent with the role that Broca’s area plays in syntactic processing, although “they fail to converge on a single region within the inferior frontal cortex” (NEWMAN et al., 2003, p.297). Differences may have arisen from differences in the demands of the tasks, design of the studies as well as the statistical methods applied in each experiment. The studies, as a group, seem to implicate the classical left-hemisphere language areas (inferior frontal and superior temporal regions) and their right homologues for syntactic processing, but as expected, activation in these regions is not specific to syntactic processing. There is large venue for future research, such as to elucidate which aspects of syntactic processing are subserved by which areas of the brain and under what circumstances. Future studies should take into account individual differences and different languages, as well as studying sentence processing within a much broader perspective, reconciling previous results and leading to more detailed models and theories. Keywords: syntactic processing; reading comprehension; literature review
How left inferior frontal cortex participates in syntactic processing: Evidence from aphasia
Brain and Language, 2008
We report on three experiments that provide a real-time processing perspective on the poor comprehension of Broca's aphasic patients for non-canonically structured sentences. In the first experiment we presented sentences (via a Cross Modal Lexical Priming (CMLP) paradigm) to Broca's patients at a normal rate of speech. Unlike the pattern found with unimpaired control participants, we observed a general slowing of lexical activation and a concomitant delay in the formation of syntactic dependencies involving ''moved'' constituents and empty elements. Our second experiment presented these same sentences at a slower rate of speech. In this circumstance, Broca's patients formed syntactic dependencies as soon as they were structurally licensed (again, a different pattern from that demonstrated by the unimpaired control group). The third experiment used a sentence-picture matching paradigm to chart Broca's comprehension for non-canonically structured sentences (presented at both normal and slow rates). Here we observed significantly better scores in the slow rate condition. We discuss these findings in terms of the functional commitment of the left anterior cortical region implicated in Broca's aphasia and conclude that this region is crucially involved in the formation of syntactically-governed dependency relations, not because it supports knowledge of syntactic dependencies, but rather because it supports the real-time implementation of these specific representations by sustaining, at the least, a lexical activation rise-time parameter. Published by Elsevier Inc.
Parametric effects of syntactic–semantic conflict in Broca’s area during sentence processing
Brain and Language, 2012
The hypothesized role of Broca's area in sentence processing ranges from domain-general executive function to domain-specific computation that is specific to certain syntactic structures. We examined this issue by manipulating syntactic structure and conflict between syntactic and semantic cues in a sentence processing task. Functional neuroimaging revealed that activation within several Broca's area regions of interest reflected the parametric variation in syntacticsemantic conflict. These results suggest that Broca's area supports sentence processing by mediating between multiple incompatible constraints on sentence interpretation, consistent with this area's well-known role in conflict resolution in other linguistic and non-linguistic tasks.
We describe an effort to map lesion to behavior by studying the comprehension of complex VP-Ellipsis constructions (e.g., The policeman defended the child, and the dedicated fireman did___ too…) in participants with Broca"s aphasia. We quantified the lesions of our individual participants using cytoarchitectonic probability maps of the human brain. We found that our Broca participants evinced delayed priming of the object in the ellipsis clause, while off-line comprehension was largely spared. Structure-function analyses revealed that lesions in both temporal and frontal areas participated in the behavioral outcomes, though each region seems to have played a distinct role.