Many explanations of the difficulties associated with interpreting object relative clauses appeal to the demands that object relatives make on working memory. MacDonald and Christiansen (2002) pointed to variations in reading experience as a source of differences, arguing that the unique word order of object relatives makes their processing more difficult and more sensitive to the effects of previous experience than the processing of subject relatives. This hypothesis was tested in a largescale study manipulating reading experiences of adults over several weeks. The group receiving relative clause experience increased reading speeds for object relatives more than for subject relatives, whereas a control experience group did not. The reading time data were compared to performance of a computational model given different amounts of experience. The results support claims for experience-based individual differences and an important role for statistical learning in sentence comprehension processes. George Miller's (1956) landmark description of the nature of short term memory was a characterization of both its limits (7 ± 2 units) and the modulation of these limits through learning, in that the units were chunks, the size of which could change through a person's experience with the material being processed. In discussions of computational capacity since that time, different research paradigms have tended to vary in their attention to the claim of capacity limits vs. the claim that capacity changes through learning. For example, within adult sentence comprehension, many accounts have invoked capacity limits to explain people's difficulties in relative clause comprehension (e.g., Gibson, 1998;Just & Carpenter, 1992;Lewis, Vasishth & VanDyke, 2006). All of these accounts have noted that experience could affect processing abilities, but the focus in these accounts has been on showing how a characterization of capacity limits explains certain aspects of sentence comprehension

We evaluated sentence comprehension of variety of sentence constructions and components of short term memory in 53 individuals with acute ischemic stroke, to test some current hypotheses about the role of Broca's area in these tasks. We found that some patients show structure-specific, task-independent deficits in sentence comprehension, with chance level of accuracy on passive reversible sentences, more impaired comprehension of object-cleft than subject-cleft sentences, and more impaired comprehension of reversible than irreversible sentences in both sentence-picture matching and enactment tasks. In a dichotomous analysis, this pattern of “asyntactic comprehension” was associated with dysfunctional tissue in left angular gyrus, rather than dysfunctional tissue in Broca's area as previously proposed. Tissue dysfunction in left Brodmann area (BA) 44, part of Broca's area, was associated with phonological short term memory (STM) impairment defined by forward digit span ≤ 4. Verbal working memory defined by backward digit span ≤ 2 was associated with tissue dysfunction left premotor cortex (BA 6). In a continuous analysis, patients with acute ischemia in left BA 44 were impaired in phonological STM. Patients with ischemia in left BA 45 and BA 6 were impaired in passive, reversible sentences, STM, and verbal working memory. Patients with ischemia in left BA 39 were impaired in passive reversible sentences, object cleft sentences, STM, and verbal working memory. Therefore, various components of working memory seem to depend on a network of brain regions that include left angular gyrus and posterior frontal cortex (BA 6, 44, 45); left BA 45 and angular gyrus (BA 39) may have additional roles in comprehension of syntax such as thematic role checking.

Background and Purpose Apraxia of speech (AOS) is an impairment of motor planning and programming of speech articulation, and is often considered an important stroke syndrome, localizable to Broca’s area. However, an influential study shed doubt on this localization, and reported that AOS is attributable to lesions of the anterior insula, based on an association between chronic AOS and anterior insula lesions. We hypothesized that chronic AOS is associated with large lesions (which include the insula) or lesions to Broca’s area. Method We tested 34 participants with chronic left supratentorial stroke on an AOS battery and obtained concurrent MRI. We evaluated associations between AOS and locations and volume of infarct. Results The presence of chronic AOS (n=17) was associated with volume of infarct, but was also associated with infarct in Broca’s area (and several other regions, but not anterior insula) in both volume-adjusted and age-adjusted linear regression and the dichotomous analysis. Carotid dissection was more common, and cardioembolism less common, as a cause of stroke in patients with AOS compared those without. Severity of AOS was also strongly associated with lesion volume. Conclusions Persistence of AOS after twelve months is associated with large left hemispheric stroke and strokes that involve Broca’s area or other relatively anterior areas to which it is structurally and/or functionally connected. Patients with such lesions may benefit from early training in the use of technologies to support speech production and communication.