Staying connected as we speak: Behavioral and tractography evidence from health and neurodegenerative disease

Abstract

For most of us, there is not a day that passes without talking. For people diagnosed with primary progressive aphasia (PPA), a rare but debilitating form of dementia, being able to speak effortlessly is no longer self-evident. The exact brain abnormalities underlying these speech impairments are still unknown. In particular, there is still no consensus on the function of the white matter pathways, or the nerve connections between different language areas in the brain. This thesis investigates the relation between speech impairments and the quality of these white matter tracts in the brain. From a fundamental scientific perspective, both major white matter routes (dorsal and ventral white matter pathways) appear to be important for language production, as part of a complex network of brain regions. From a clinical point of view, conducting experimental tasks and theory-based language tests has proven to be feasible and valuable for improvement of the diagnostic process of PPA.