Broca's aphasia is associated with a single pattern of comprehension performance: a reply

fMRI adaptation dissociates syntactic complexity dimensions

The current fMRI adaptation study sought to elucidate the dimensions of syntactic complexity and their underlying neural substrates. For the first time with fMRI, we investigated repetition suppression (i.e., fMRI adaptation) for two orthogonal dimensions of sentence complexity: embedding position (right-branching vs. center-embedding) and movement type (subject vs. object). Two novel results were obtained: First, we found syntactic adaptation in Broca's area and second, this adaptation was structured. Anterior Broca's area (BA 45) selectively adapted to movement type, while posterior Broca's area (BA 44) demonstrated adaptation to both movement type and embedding position (as did left posterior superior temporal gyrus and right inferior precentral sulcus). The functional distinction within Broca's area is critical not only to an understanding of the functional neuroanatomy of language, but also to theoretical accounts of syntactic complexity, demonstrating its multi-dimensional nature. These results implicate that during syntactic comprehension, a large network of areas is engaged, but that only anterior Broca's area is selective to syntactic movement.

Speech and language functions that require a functioning Broca's area

A number of previous studies have indicated that Broca's area has an important role in understanding and producing syntactically complex sentences and other language functions. If Broca's area is critical for these functions, then either infarction of Broca's area or temporary hypoperfusion within this region should cause impairment of these functions, at least while the neural tissue is dysfunctional. The opportunity to identify the language functions that depend on Broca's area in a particular individual was provided by a patient with hyperacute stroke who showed selective hypoperfusion, with minimal infarct, in Broca's area, and acutely impaired production of grammatical sentences, comprehension of semantically reversible (but not non-reversible) sentences, spelling, and motor planning of speech articulation. When blood flow was restored to Broca's area, as demonstrated by repeat perfusion weighted imaging, he showed immediate recovery of these language functions. The identification of language functions that were impaired when Broca's area was dysfunctional (due to low blood flow) and recovered when Broca's area was functional again, provides evidence for the critical role of Broca's area in these language functions, at least in this individual.

Effects of syntactic features on sentence-picture matching in Broca's aphasics: a reply to Drai and Grodzinksy (2005)

We reanalyzed the data in , considering individual patients' responses to different sentence types to be non-independent events. The analyses revealed effects of two of the three factors identified by Drai and Grodzinsky--constituent movement and passive mood. The result is inconsistent with the trace deletion hypothesis; we conclude that features of syntactic structure other than constituent movement are relevant to understanding performance variation in patients with Broca's aphasia.

Aphasic Deficits in Syntactic Processing

Two main classes of theories of deficits in syntactic processing in aphasia have been suggested: impairments affecting specific syntactic operations and reductions in resources available for syntactic processing. This paper reviews the data upon which such theories are based and argues that they may support only the latter type of model.

Neuropsychology and linguistic aphasiology: Evidence in favor of case studies

Two aphasic patients speaking Brazilian Portuguese and presenting the characteristics of Broca's aphasics were analyzed in relation to their capacities to express null subjects in two different grammatical persons: 1st and 3rd persons. The analysis consisted of looking at the means obtained from the two aphasic patients and their individual results concerning the production of null subjects in each grammatical person on focus. The individual pattern shown by each patient indicated the relevancy of analyzing individually the performance of neuropsychological patients. In this way the hypothesis which claims that in Brazilian Portuguese the null subject has two different natures could be verified.

Comprehension of sentences with stylistic inversion by French aphasic patients

Three French-speaking agrammatic aphasics and three French-speaking Conduction aphasics were tested for comprehension of Active, Passive, Cleft-Subject, Cleft-Object, and Cleft-Object sentences with Stylistic Inversion using an object manipulation test. The agrammatic patients consistently reversed thematic roles in the latter sentence type, and the Conduction aphasics performed at chance. The results are discussed in relationship to existing models of aphasic impairments in assigning syntactic structures and using them to determine thematic roles in sentences. We conclude that the results for the agrammatic patients demonstrate the importance of compensatory mechanisms underlying aphasic comprehension and the results in the Conduction aphasics indicate the importance of working memory deficits in determining such deficits. The results are also relevant to models of normal syntactic structure.

Computerized approaches to communication retraining after stroke

Augmentative and alternative communication (AAC) strategies traditionally have been designed for individuals for whom oral speech is not a viable option. Common clinical practice has expanded AAC use to a tool for cognitive retraining or remediation. Although technologic developments offer the potential for vastly improved communication and inclusion for some individuals with severe communication disorders, technology alone does not result in successful communication. Although AAC interventions have become increasingly common across the age range, the research base underlying the design of AAC technology, intervention strategies, and treatment potential across communication disorders remains quite limited. To move beyond the traditional application of AAC strategies as a communication modality for persons with severe motor disorders to applications for persons with cognitive/linguistic disorders, three interrelated areas of research requiring further investigations are discussed. These include the following: use of AAC as a research tool to provide theoretical insights into the nature of normal and impaired language and cognition; development of AAC strategies as treatment tools to facilitate language recovery and use (production and comprehension); and studies that evaluate the efficacy of applying AAC strategies as communication modalities for individuals with acquired cognitive/linguistic communication disorders.

Verbs: some properties and their consequences for agrammatic Broca's aphasia

It has repeatedly been shown that agrammatic Broca's aphasics have serious problems with the retrieval of verbs on action naming tests (Miceli, Silveri, Villa & Caramazza, 1984; Kohn, Lorch & Pearson, 1989; Basso, Razzano, Faglioni & Zanobio, 1990; Jonkers, 1998; Kim & Thompson, 2000). Less attention has been paid to the production of verbs at the sentence level (but see Miceli, Mazzuchi, Menn & Goodglass, 1983; Thompson, Shapiro, Li & Schendel, 1995; Thompson, Lange, Schneider & Shapiro, 1997; Bastiaanse & Van Zonneveld, 1998; Bastiaanse, Rispens & Van Zonneveld, 2000; Friedmann, 2000), although it has been mentioned that in agrammatic spontaneous speech verbs are lacking (Saffran, Berndt & Schwartz, 1989; Thompson et al., 1995, but see Bastiaanse & Jonkers, 1998).In this paper, three cross-linguistic studies are discussed to show that these problems with verbs have consequences for other grammatical morphemes and structures that have been mentioned to be impaired in agrammatic speech and that these consequences are different per language, depending on linguistic characteristics. The first study focuses on finiteness and compares the production of finite verbs in matrix and embedded clauses in Dutch and English, showing that a linguistic rule in Dutch (Verb Second), which does not exist in English, can explain the different performance of Dutch and English agrammatic Broca's aphasics. The second study focuses on determiners and (finite) verbs in German and shows that poor determiner production is directly related to poor verb production. The last study demonstrates that the ability to construct negative sentences is dependent on the language specific relation between verb movement and negation: Dutch and Norwegian agrammatics perform equally well on affirmative and negative sentences, whereas English and Spanish agrammatics are more impaired on negative sentences.Overall, these studies show that the problems agrammatics encounter with verbs and their properties have a spin-off on the production of other word-classes and that the characterization 'problems with grammatical morphemes' is too general for telegraphic speech.

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

Event-related functional magnetic resonance imaging was used to investigate the localization of syntactic processing in sentence comprehension. Matched pairs of sentences containing identical lexical items were compared. One member of the pair consisted of a syntactically simpler sentence, containing a subject relativized clause. The second member of the pair consisted of a syntactically more complex sentence, containing an object relativized clause. Ten subjects made plausibility judgments about the sentences, which were presented one word at a time on a computer screen. There was an increase in BOLD hemodynamic signal in response to the presentation of all sentences compared to fixation in both right and left occipital cortex, the left perisylvian cortex, and the left premotor and motor areas. BOLD signal increased in the left angular gyrus when subjects processed the complex portion of syntactically more complex sentences. This study shows that a hemodynamic response associated with processing the syntactically complex portions of a sentence can be localized to one part of the dominant perisylvian association cortex.