Left hemisphere plasticity and aphasia recovery.

A recent study by our group revealed a strong relationship between functional brain changes in the left hemisphere and anomia treatment outcome in chronic stroke patients (N=26) with aphasia (Fridriksson, 2010). The current research represents a continuation of this work in which we have refined our methods and added data from four more patients (for a total sample size of 30) to assess where in the left hemisphere treatment-related brain changes occur. Unlike Fridriksson (2010) which only focused on changes in correct naming as a marker of treatment outcome, the current study examined the relationship between changes in left hemisphere activity and changes in correct naming, semantic paraphasias, and phonemic paraphasias following treatment. We also expanded on the work by Fridriksson by examining whether neurophysiological measures taken at baseline (defined henceforth as the time-point before the start of anomia treatment) predict treatment outcome. Our analyses revealed that changes in activation in perilesional areas predicted treatment-related increases in correct naming in individuals with chronic aphasia. This relationship was most easily observed in the left frontal lobe. A decrease in the number of semantic and phonemic paraphasias was predicted by an activation change in the temporal lobe involving cortical areas that were shown to be active during picture naming in 14 normal subjects. In contrast, a far less certain relationship was found between baseline neurophysiological measures and anomia treatment outcome. Our findings suggest that improved naming associated with behavioral anomia treatment in aphasia is associated with modulation of the left frontal lobe whereas a reduction in naming errors is mediated by left posterior regions that classically are thought to be involved in language processing.