APA Dictionary of Psychology

n. a class of neurodegenerative disorders defined by the pathological aggregation of abnormal tau protein in the brain, leading to microtubule dysfunction, neuronal and/or glial injury, and progressive neurological impairment. In healthy brains, tau stabilizes microtubules to maintain neuronal structure and transport; in tauopathies, hyperphosphorylated tau detaches, misfolds, and aggregates, disrupting these processes and driving neurodegeneration. Tauopathies may be primary, in which tau pathology is the central driver of disease (e.g., progressive supranuclear palsy, corticobasal degeneration, Pick's disease), or secondary, in which tau pathology occurs downstream of another process, most commonly amyloid-β plaques (e.g., Alzheimer's disease). Disease expression depends on the tau isoform involved (e.g., 3-repeat [3R], 4-repeat [4R], mixed) and the neuroanatomical distribution of pathology, but can include cognitive impairment (executive dysfunction, slowed processing speed), behavioral features (apathy, emotional blunting), language disturbances (dysarthria, apraxia of speech), and motor dysfunction (parkinsonism, myoclonus, motor planning deficits). Management is symptomatic, multidisciplinary, and supportive, with treatment tailored to the dominant clinical syndrome.