Evidence for the solidarity of the expressive and receptive language systems: a retrospective study.

A strong tendency toward left hemisphere (LH) language dominance has been well established, as evidenced by the high prevalence of language impairment following sudden onset lesions in the LH. In the presence of progressive LH pathology, such as epilepsy, substantial deviations in language organization can occur. However, the question regarding whether reorganization involves both expressive and receptive language functions or only the one directly affected by the primary location of pathology has not been settled. Using Wada testing scores from 296 epilepsy patients and estimated rates of typical dominance in the normal population, we assessed the frequency with which left frontal and temporal pathology resulted in reorganization of only the expressive or receptive language function or both. The comparisons revealed: (1) a significantly higher prevalence of atypical organization (i.e., deviations from LH dominance) among the LH patients compared to normal population estimates and right hemisphere patients, and (2) that regardless of pathology location within the LH, the rates of atypical reorganization for both expressive and receptive language were essentially equal. These results constitute evidence that the two language functions are intimately yoked and that when disruption to the system results in reorganization, it usually yields functional changes throughout the system.