Gesture profiles distinguish primary progressive aphasia variants

Abstract

Primary progressive aphasia (PPA) is a neurodegenerative syndrome characterized by progressive language deficits. The main variants of PPA - semantic (svPPA), logopenic (lvPPA), and nonfluent (nfvPPA) - can be challenging to distinguish. Limb apraxia often co-occurs with PPA, but it is unclear whether PPA variants are associated with different apraxia patterns. Prior evidence from stroke indicates that temporal lobe lesions are associated with reduced benefit of meaning in gesture imitation tasks and disproportionate deficits in imitation of object manipulation-related hand postures compared to arm kinematics. We tested the hypothesis that svPPA - who primarily exhibit temporal lobe atrophy - would differentially show this pattern. Participants with PPA completed meaningful and meaningless gesture imitation tasks. Performance was scored for hand posture and arm kinematics. Mixed-effect models controlling for dementia severity showed showed a critical interaction between variant, meaning, and gesture component: unlike lvPPA and nfvPPA, svPPA's hand postures failed to benefit from gesture meaning. This research extends prior findings on the role of the temporal lobe in action representations associated with manipulable objects, and is the first to indicate distinct gesture imitation patterns as a function of PPA variant. Characterizing gesture deficits in PPA may help inform diagnostics, compensatory communication strategies, and models of praxis.