NEFL and primary progressive aphasia: AD, Alzheimer’s disease; AI, artificial intelligence; Aβ, amyloid-beta; CSF, cerebrospinal fluid; FDG, fluorodeoxyglucose; FTLD, frontotemporal lobar degeneration; IFG, inferior frontal gyrus; lvPPA, logopenic variant of primary progressive aphasia; MRI, magnetic resonance imaging; NfL, neurofilament light chain; nfvPPA, nonfluent/agrammatic variant of primary progressive aphasia; PET, positron emission tomography; p-tau, phosphorylated tau protein; svPPA, semantic variant of primary progressive aphasia.