Environmental sound processing in primary progressive aphasia: behavioral deficits and their neural correlates

Understanding environmental sound recognition provides insight into the neural and cognitive mechanisms underlying nonverbal auditory semantics. In this study, we investigated the clinical characteristics and neural correlates of environmental sound recognition impairments in primary progressive aphasia (PPA). Fifty-three patients with PPA (25 non-fluent/agrammatic, nine semantic, five logopenic, and 14 unclassified), age-matched healthy controls, and patients with other dementia syndromes were examined. Audiological measures included pure-tone thresholds, verbal sound recognition (phoneme identification), and auditory temporal acuity. Neuropsychological testing and neuroimaging with magnetic resonance imaging and N-isopropyl-p- 123 I-iodoamphetamine single-photon emission computed tomography were performed. Environmental sound recognition was assessed using sound-to-picture-and-word matching tasks. Across PPA subtypes, performance correlated with naming, auditory word comprehension, two-way anomia reflecting semantic memory deficits, and category fluency; however, not with basic auditory measures. Impairment was associated with reduced regional cerebral blood flow in the left posterior temporal-temporoparietal regions, and this association remained significant after accounting for regional atrophy. These findings suggest that environmental sound recognition deficits across PPA subtypes are unlikely to be explained solely by basic auditory dysfunction and may involve disruption of posterior auditory-semantic interface regions. (180)