Approximately 20-40% of stroke survivors suffer from aphasia, the partial or complete loss of language processing. It has been observed that patients with aphasia will typically make the same number of naming errors every time tested, but the objects that are named correctly or incorrectly will vary. These errors are therefore not linked to specific objects, but are instead related to faulty language processing. It remains poorly understood how the language processing can vary between right or wrong to enable correct naming. Here, we use functional imaging to identify processing patterns that lead to successful language production in patients with chronic aphasia. This could provide a potentially meaningful target for future rehabilitation methods.
Methods: We analyzed data from 36 individuals with chronic aphasia who completed a picture-naming task while undergoing functional neuroimaging. After mapping the functional data to the AICHA atlas, regional activation signal was analyzed for each response type (correct, semantic paraphasia, or phonemic paraphasia). We performed a ttest looking for significant differences in activation at particular regions of interest for correct naming compared to semantic and phonemic paraphasias for each individual.
Results: Individuals recruit variable regions for correctly named objects. There are some regions that stand out as being statistically significant (p ≤ 0.05) for correct productions compared to semantic and phonemic paraphasias across several subjects (e.g., insular regions were statistically significant for 8/36 subjects and superior temporal sulcus for 9/36 subjects). Also, there is variability in whether the regions that were statistically different were peri-lesional or in unaffected, healthy tissue.
Discussion: There is evidence that individualized functional recruitment utilized by people with chronic aphasia allows for correctly naming objects. This pattern is unique and widely variable across subjects, due in large part to differences in lesion size and location. However, individuals recruit a particular network of peri-lesional and preserved brain tissue that is different for correctly naming objects compared to incorrectly naming objects (with semantic or phonemic paraphasias)