In many individuals with acquired aphasia, language function improves to some extent over time. This recovery process is thought to depend on neuroplasticity, that is, functional reorganization of brain regions involved in language processing. There is great interest in characterizing this reorganization process, and determining whether it can be facilitated by behavioral, neuromodulatory or pharmacological interventions. However, a major roadblock to this line of research is that it is challenging to identify language regions of the brain in individuals with aphasia. Tasks commonly used to engage language processing, such as narrative comprehension and picture naming, are limited in terms of validity (identification of language regions, and not other regions) and reliability (test-retest reproducibility). On the other hand, paradigms such as semantic decision that are effective in mapping language in people without aphasia (for instance, presurgical patients), are typically too challenging for people with aphasia. The overall goal of this study is to develop an adaptive semantic matching paradigm that can be successfully performed by people with aphasia, and that is valid and reliable in identifying language regions in individual patients. The key innovation is an adaptive staircase procedure whereby each individual is presented with stimuli that are challenging yet within their competence, so that language processing can be fully engaged in people with and without language disorders. The feasibility, validity and reliability of this adaptive semantic matching paradigm will be evaluated and compared to two commonly used paradigms: narrative comprehension and picture naming. It is hypothesized that the adaptive semantic matching paradigm will be more effective than these commonly used paradigms. The experimental control scripts, stimuli, and normative brain imaging data will be made freely available to other researchers. Moreover, this study will establish a formal framework for quantifying feasibility, validity and reliability of language mapping paradigms in this clinical research context, so that other potential approaches can be similarly evaluated.
Studies on functional reorganization of language regions of the brain critically depend on the ability to identify language regions in individual patients and quantify any changes that take place over time. The absence of psychometrically sound language mapping paradigms that are feasible in individuals with aphasia is a significant roadblock to this research. The proposed study will develop an adaptive semantic matching paradigm that will provide a foundation for future research on neuroplasticity of language regions.
