Repeating with the right hemisphere: reduced interactions between phonological and lexical-semantic systems in crossed aphasia?

Abstract

Knowledge on the patterns of repetition amongst individuals who develop language deficits in association with right hemisphere lesions (crossed aphasia) is very limited. Available data indicate that repetition in some crossed aphasics experiencing phonological processing deficits is not heavily influenced by lexical-semantic variables (lexicality, imageability, and frequency) as is regularly reported in phonologically-impaired cases with left hemisphere damage. Moreover, in view of the fact that crossed aphasia is rare, information on the role of right cortical areas and white matter tracts underpinning language repetition deficits is scarce. In this study, repetition performance was assessed in two patients with crossed conduction aphasia and striatal/capsular vascular lesions encompassing the right arcuate fasciculus (AF) and inferior frontal-occipital fasciculus (IFOF), the temporal stem and the white matter underneath the supramarginal gyrus. Both patients showed lexicality effects repeating better words than non-words, but manipulation of other lexical-semantic variables exerted less influence on repetition performance. Imageability and frequency effects, production of meaning-based paraphrases during sentence repetition, or better performance on repeating novel sentences than overlearned clichés were hardly ever observed in these two patients. In one patient, diffusion tensor imaging disclosed damage to the right long direct segment of the AF and IFOF with relative sparing of the anterior indirect and posterior segments of the AF, together with fully developed left perisylvian white matter pathways. These findings suggest that striatal/capsular lesions extending into the right AF and IFOF in some individuals with right hemisphere language dominance are associated with atypical repetition patterns which might reflect reduced interactions between phonological and lexical-semantic processes.

Dissecting the function of networks underpinning language repetition

“…In this study, De-Torres et al ( 2013 ) show that repetition after subcortical lesions involving the dorsal and ventral streams in patients who are right-hemisphere dominant for language is not heavily influenced by lexical-semantic variables as is regularly reported in similar cases with left hemisphere damage.…”

Cholinergic Potentiation and Audiovisual Repetition-Imitation Therapy Improve Speech Production and Communication Deficits in a Person with Crossed Aphasia by Inducing Structural Plasticity in White Matter Tracts

“…Before advancing further in the interpretation of our results, data from JAM should be interpreted with caution because he had atypical brain-language organization (see De-Torres et al, 2013 ). JAM had both an atypical lateralization of language in the right hemisphere and a rare form of crossed aphasia (subcortical CA) ( Alexander et al, 1989 ; Jung et al, 2010 ).…”

“…JAM was a 46-year-old right-handed, monolingual male with no history of neurological diseases, no family history of left-handedness, and normal developmental milestones (see further details in De-Torres et al, 2013 ). His personal history was remarkable for hypertension and type II diabetes.…”

“…In the baseline assessments, it was noted that JAM presented no difficulty in repeating single words and some non-words, showing variable difficulty with the repetition of two-word and three-word lists and sentences (see De-Torres et al, 2013 ). Therefore, the aphasia therapy program was tailored to treat the greater JAM’s difficulty: sentence repetition (see Salis et al, 2015 ; Eom and Sunga, 2016 ) with the aim of improving speech fluency ( Kohn et al, 1990 ).…”

“…Language and communication were assessed twice before initiating the treatment. The first linguistic evaluation was performed in September 2011 (at the end of general cognitive testing) (see De-Torres et al, 2013 ), whereas the second linguistic evaluation was performed in April 2012. JAM patient did not receive any type of speech and language therapy between the first and second baseline evaluations.…”