Language processing in frontotemporal dementia: A brief review

Frontotemporal dementia (FTD) is a neurodegenerative condition that presents with a number of distinct behavioral phenotypes. Here we review languageprocessing deficits in three subgroups of FTD patients: progressive nonfluent aphasia (PNFA), semantic dementia (SD), and nonaphasic FTD patients with a disorder of social and executive functioning (SOC/EXEC). These three clinical subgroups have contrasting patterns of regional cortical atrophy that can be linked to their language impairments. PNFA patients' disease includes left ventral inferior frontal cortex, resulting in impaired grammatical processing. SD patients demonstrate a profound impairment for semantic knowledge related to atrophy of the left temporal lobe. SOC/EXEC patients' frontal atrophy tends to be more right lateralized and is associated with declines in executive functioning. SOC/EXEC patients' limited executive resources impact language processing in a variety of ways, including slowed grammatical processing and impaired narrative discourse. FTD patients therefore provide converging evidence regarding dissociable components of language processing and their neuroanatomical bases.