APA Dictionary of Psychology

a progressive neuropathological process and heterogeneous group of neurodegenerative disorders characterized by focal atrophy in the frontal and/or temporal lobes, resulting from specific proteinopathies (e.g., tau, TDP-43, FUS). It primarily presents with social, emotional, and behavioral symptoms, including dysregulated social and personal conduct and diminished emotional responsiveness, with additional language, executive function, and motor deficits that vary by subtype. Major syndromes associated with frontotemporal lobar degeneration include the behavioral variant of frontotemporal dementia (bvFTD), associated primarily with behavioral and personality changes; the nonfluent (agrammatic) variant of primary progressive aphasia (nfvPPA), associated with progressive deficits in speech, grammar, and word production; and the semantic variant of PPA (svPPA), involving deficits in semantic knowledge and naming. Some patients display extrapyramidal symptoms, which may form part of either corticobasal syndrome due to corticobasal degeneration or progressive supranuclear palsy, while others present with overlapping motor neuron disease (FTD with amyotrophic lateral sclerosis or motor neuron disease).