On the Role of the Anterior Superior Temporal Lobe in Language Processing: Hints from Functional Neuroimaging Studies (original) (raw)
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Broca's aphasia, Broca's area, and syntax: A complex relationship
Behavioral and Brain Sciences, 2000
Advances in neuroimaging technology have increased our knowledge of the neuroanatomy of higher functions of the central nervous system: It is now possible to get a glimpse of the brain while it is in action. However, this progress would not have been possible without improved understanding of the knowledge base and operations that underlie complex behavior. Parallel to the greater precision of the technology, some progress has been made in our understanding of the cognitive architecture that underlies certain behavioral domains. In the study of brain-language relations, theoretical developments in linguistics have gone hand in hand with imaging, making a joint contribution to behavioral neurology. After several decades of the study of language and the brain from a linguistic angle, there is now a relatively dense body of facts that can be seriously evaluated. This target article will review central results and use them to motivate some novel conclusions about the representation of language in the human cerebral cortex. The discussion will revolve around the choice of unit of behavioral analysis and its theoretical import. An outlook on language derived from current linguistic theory can lead to a new and more precise picture of language and the brain.
Agrammatic Broca's Aphasia Is Not Associated with a Single Pattern of Comprehension Performance
Brain and Language, 2001
One influential hypothesis posits that the brain regions implicated in Broca's aphasia are responsible for specific syntactic operations that are necessary for the comprehension and production of sentences ). The empirical basis of this hypothesis is the claim that Broca's aphasics have no difficulty understanding sentences in the active voice (and other ''canonical'' sentence types, such as subject relatives and clefts with agentive predicates), but perform at chance level with passive voice constructions (and other ''noncanonical'' sentences such as object-gap relatives and object clefts). In the face of wellestablished results indicating that Broca's aphasics can exhibit several different performance patterns on these sentence types, argued that these conflicting results do not challenge the theory when the data are analyzed appropriately. They carried out a creative statistical analysis of the comprehension performance of published cases of Broca's aphasia and concluded that all of these cases are in agreement with the predicted pattern: chance on passives and 100% correct on actives. Here we show that the statistical reasoning adopted by is flawed. We also show that the comprehension performance of a substantial number of the Broca's aphasics in their own sample does not conform to the pattern required. Rather, contrary to these authors' claim, Broca's aphasia is not associated with a consistent pattern of sentence comprehension performance, but allows for a number of distinct patterns in different patients.
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.
Broca's Aphasia Is Associated with a Single Pattern of Comprehension Performance: A Reply
Brain and Language, 2001
Over many years now, we have provided evidence that the cortical area associated with Broca's aphasia sustains operations necessary for the analysis of syntactic constructions that contain displaced constituents. A massive body of empirical datafrom comprehension, real-time processing, and grammaticality judgment-shows that Broca's area supports mechanisms involved in the computation of transformational relations (cf. Zurif, 1995; Grodzinsky, 2000). This evidence has been challenged and debated-most recently in the pages of this journal. Thus in 1999 we published the results of a survey of comprehension scores for Broca's patients conventionally selected via the Boston Diagnostic Aphasia Exam (Goodglass & Kaplan, 1972) and other like instruments (Grodzinsky, Piñango, Zurif, & Drai, 1999; GPZD henceforth). We included all the relevant data published between 1980 and 1996 of which we were aware. The picture that emerged from these data was very clear: The Broca's patients as a group performed significantly above chance level in their comprehension of structures without displaced constituents-actives, subject relatives, and subject-clefts; in contrast, they were at chance level in their comprehension of transformationally derived structures (those with displaced phrases), i.e., on passives, object relatives, and object-clefts. For one particular instance of this generalization-the active/passive contrast-there exists a considerable body of experimental evidence, obtained at different times and in different laboratories.
The brain basis of syntactic processes: functional imaging and lesion studies
NeuroImage, 2003
Language comprehension can be subdivided into three processing steps: initial structure building, semantic integration, and late syntactic integration. The two syntactic processing phases are correlated with two distinct components in the event-related brain potential, namely an early left anterior negativity (ELAN) and a late centroparietal positivity (P600). Moreover, ERP findings from healthy adults suggest that early structure-building processes as reflected by the ELAN are independent of semantic processes. fMRI results have revealed that semantic and syntactic processes are supported by separable temporofrontal networks, with the syntactic processes involving the left superior temporal gyrus (STG), the left frontal operculum, and the basal ganglia (BG) in particular. MEG data from healthy adults have indicated that the left anterior temporal region and the left inferior frontal region subserve the early structure building processes. ERP data from patients with lesions in the left anterior temporal region and from patients with lesions in the left inferior frontal gyrus support this view, as these patients do not demonstrate an ELAN, although they do demonstrate a P600. Further results from patients with BG dysfunction suggest that parts of this subcortical structure are involved in late syntactic integrational processes. The data from the different experiments lead to the notion of separable brain systems responsible for early and late syntactic processes, with the former being subserved by the inferior frontal gyrus and the anterior STG and the latter being supported by the BG and more posterior portions of the STG.
Semantic Operations in Aphasic Comprehension: Implications for the Cortical Organization of Language
Brain and Language, 2001
We provide data on the neurological basis of two semantic operations at the sentence level: aspectual coercion and complement coercion. These operations are characterized by being purely semantic in nature; that is, they lack morphosyntactic reflections. Yet, the operations are mandatory (i.e., they are indispensable for the semantic well formedness of a sentence). Results indicate that, whereas Broca's patients have little or no trouble understanding sentences requiring these operations (performance was above chance for all conditions), Wernicke's patients performed at normal-like levels only for sentences that did not require these operations. These findings suggest that sentence-level semantic operations rely very specifically on the integrity of the cortical area associated with Wernicke's aphasia, but not on the region corresponding to Broca's aphasia. In the context of other findings from lesion and imaging studies, this evidence allows a view of the cortical distribution of language capacity that is drawn along a linguistic line, one which distinguishes syntactic from semantic operations.
Brain and Cognition, 2005
We examined the effect of localized brain lesions on processing of the basic speech acts (BSAs) of question, assertion, request, and command. Both left and right cerebral damage produced significant deficits relative to normal controls, and left brain damaged patients performed worse than patients with right-sided lesions. This finding argues against the common conjecture that the right hemisphere of most right-handers plays a dominant role in natural language pragmatics. In right-hemisphere damaged patients, there was no correlation between location and extent of lesion in perisylvian cortex and performance on BSAs. By contrast, processing of the different BSAs by left hemisphere-damaged patients was strongly affected by perisylvian lesion location, with each BSA showing a distinct pattern of localization. This finding raises the possibility that the classical left perisylvian localization of language functions, as measured by clinical aphasia batteries, partly reflects the localization of the BSAs required to perform these functions.