Unspeakable motion: Selective action-verb impairments in Parkinson’s disease patients without mild cognitive impairment

•We examined processing of action verbs and nouns in Parkinson’s disease (PD).•We assessed patients with and without mild cognitive impairment (PD-MCI and PD-nMCI).•In PD-MCI, deficits emerged for both action verbs and manipulable nouns.•In PD-nMCI, only action verbs with high motion content were disrupted.•Action-verb deficits may represent an early, sui generis alteration in PD.