Abstract
Individuals with a diagnosis of specific language impairment (SLI) show abnormal spoken language occurring alongside normal non-verbal abilities. Behaviorally, people with SLI exhibit diverse profiles of impairment involving phonological, grammatical, syntactic, and semantic aspects of language. In this study, we used a multimodal neuroimaging technique called anatomically constrained magnetoencephalography (aMEG) to measure the dynamic functional brain organization of an adolescent with SLI. Using single-subject statistical maps of cortical activity, we compared this patient to a sibling and to a cohort of typically developing subjects during the performance of tasks designed to evoke semantic representations of concrete objects. Localized patterns of brain activity within the language impaired patient showed marked differences from the typical functional organization, with significant engagement of right hemisphere heteromodal cortical regions generally homotopic to the left hemisphere areas that usually show the greatest activity for such tasks. Functional neuroanatomical differences were evident at early sensoriperceptual processing stages and continued through later cognitive stages, observed specifically at latencies typically associated with semantic encoding operations. Our findings show with real-time temporal specificity evidence for an atypical right hemisphere specialization for the representation of concrete entities, independent of verbal motor demands. More broadly, our results demonstrate the feasibility and potential utility of using aMEG to characterize individual patient differences in the dynamic functional organization of the brain.
Highlights
Children with receptive or expressive language impairments who have normal hearing, an ordinary environment and rearing experiences, and show no other signs of developmental or neurological disorder are diagnosed with specific language impairment (SLI)
The primary purpose of our study was to test the feasibility and usefulness of anatomically constrained MEG for making direct comparisons between individual patients and typically developing control subjects in the dynamic functional organization of the brain. Using this multimodal functional neuroimaging technique, which provides the uncommon ability to localize cortical activity with millisecond temporal resolution, our findings revealed in an individual patient with a history of developmental language disorder an atypical right hemisphere specialization for the semantic representation of concrete entities
Using single-subject statistical maps, this patient showed strongly right-lateralized brain responses during the successful performance of a task that requires the evocation of semantic representations of visual objects when no spoken verbal response was required
Summary
Children with receptive or expressive language impairments who have normal hearing, an ordinary environment and rearing experiences, and show no other signs of developmental or neurological disorder are diagnosed with specific language impairment (SLI). Neurological and cognitive neuroscientific studies of functional brain organization demonstrate a prominent role of the left cerebral hemisphere generally in receptive and expressive language as well as for the representation of semantic information, including word meanings and object concepts (Vigneau et al, 2006). Despite undergoing significant developmental changes (Schlaggar et al, 2002; Brown et al, 2005; Szaflarski et al, 2006) and commonly involving regions of the right hemisphere as well (Martin and Chao, 2001; Binder and Desai, 2011; Donnelly et al, 2011), the typically developing cerebral functional organization for encoding word and object meanings shows a left hemisphere prominence (Martin, 1999) that is present even during infancy (Travis et al, 2011)
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