Comparing two Italian picture naming tasks: insights from an FDG PET study in Primary Progressive Aphasia

Picture naming constitutes one of the most effective neuropsychological tools to evaluate language impairments. Despite its apparent simplicity, impairments of various nature can be found in the clinical population. The study aims to provide critical considerations for selecting and using picture naming tests in clinical practice for Primary Progressive Aphasia (PPA). To achieve the goal, we focused on CaGi and SAND Italian naming tests. Firstly, we examined the accuracy and the qualitative errors profile in 52 PPA patients. We evaluated the capacity of both tests to discriminate patients from healthy controls (HC), and between PPA variants (semantic sv-PPA; non-fluent nfv-PPA; logopenic lv-PPA). Secondly, we explored how different psycholinguistic variables affected performance. Finally, we investigated brain metabolism with FDG-PET in 6 Regions of Interest. Behavioural results suggested that SAND and CaGi differed in terms of accuracy and errors profile, suggesting that SAND is more difficult than CaGi, as revealed by reduced accuracy. Both tests distinguished between HC and PPA, nonetheless only SAND was able to discriminate among variants. Imaging findings revealed a correlation between hypometabolism in the left anterior fusiform gyrus, naming accuracy, and semantic errors in both tests, as well as SAND anomic errors, in the whole sample. Left temporal pole hypometabolism was associated to accuracy in both tests, and semantic errors in CaGi. Again, accuracy and semantic errors in CaGi correlated with hypometabolism in the left posterior fusiform gyrus in the sv-PPA group. To conclude, in absence of imaging data SAND may be better at highlighting subtle distinctions between PPA variants, namely to be suitable in diagnosis, whereas CaGi may be useful for a detailed characterization on of the nature of the impairments, more suitable 7 possible rehabilitation settings. The theoretical and practical implications of the empirical findings are discussed. Keywords: Primary Progressive Aphasia, picture naming, semantic errors, FDG-PET.