Exploring the cognitive basis of right-hemisphere pragmatic language disorders.

Despite considerable interest in the linguistic dimensions of right-hemisphere (RH) pragmatic language disorders, the cognitive bases for these are rarely examined. This study investigated two alternative explanations. First, RH pragmatic language disorders may reflect failure of the RH to synthesise incoming and preexisting information, verbal and visuospatial. In this case language and visuospatial performance should covary. Alternatively such disorders may reflect damage to executive control of all cognitive processing secondary to frontal system failure. In this case language and executive function would be associated. Further, in the former case, subjects should be insensitive to the plausibility of information, whereas in the latter they would be fixated by the literal meaning of information and therefore highly sensitive to plausibility. Eighteen patients with RH damage were compared to 20 matched controls on a range of language and neuropsychological tasks. Pragmatic performance was generally correlated to RH (visuospatial) function, not to executive function. Nonetheless RH patients were found to have problems ignoring plausibility. Thus the specific RH hypothesis described needs to be reconsidered.