Mapping aphasic symptoms to the post-stroke brain

The neural correlates of aphasic errors in spontaneous language are largely unknown. The impact of the right hemisphere (RH) is of particular interest, as its role in aphasic language production and functional recovery is disputed. With event-related fMRI and a detailed linguistic evaluation schema we analysed picture descriptions generated by 12 aphasic participants and compared different error categories to unimpaired language. We found differential effects for the aphasic symptoms, most frequently in RH homologues of speech- and language-relevant areas that were not active during unimpaired language production. Additionally, we report left-hemisphere areas associated with executive functions or monitoring. For the RIFG, we found a similar functional segregation as reported for unimpaired speakers in the LIFG. We interpret the marked involvement of the RH during aphasic symptoms as the attempt to compensate for occurring errors which, though, remains unsuccessful, possibly due to restricted language processing capacities of the RH