Right hemisphere involvement in intensive aphasia therapy outcomes: a multimodal neuroimaging concept study

Few studies investigated factors that predict intensive language therapy (ILT) outcome. This study aimed to analyze multimodal neural factors that possibly underly ILT success.

Lesion volume and DTI analyses were performed with 17 aphasic individuals, and complemented by fMRI analysis in 12 patients (due to drop-outs). Structural and functional data were collected at the beginning of a seven week ILT program and correlated with language changes, measured using the Aachen Aphasia Test. Additionally, all analyses were correlated with the patients' initial aphasia severity.

Therapy success was associated with functional activity in right inferior and middle temporal gyri, bilateral superior frontal gyrus/ adjacent anterior cingulate cortex, and right occipital lobe (lingual gyrus, fusiform gyrus, lateral occipital cortex). Statistically uncorrected DTI analysis (p(uncorr) < .001) revealed a positive correlation between language improvement and structural integrity in the right temporal lobe and two left-hemisphere white matter clusters (frontal, parietal). Neither global nor language-specific lesion volume was correlated with therapy outcome. However, lesion volume in insula, putamen and white matter tracts was correlated with initial aphasia severity.

Our preliminary results suggest a predictive role of right temporal structures and functional activation in areas associated with healthy language processing. They also indicate a contribution of functional activation in brain areas associated with cognitive control and non-linguistic semantic processing. Further, lesion volume in both global and language-specific structures proved relevant for the initial severity of aphasia but not for recovery potential following ILT. Our results should be regarded as hypothesis-generating for future research.