Comparing two picture naming tasks in Primary Progressive Aphasia: insights from behavioural and neural results

Abstract

AbstractBackgroundPicture naming tests are widely used to evaluate language impairments, especially in Primary Progressive Aphasia (PPA). The available instruments differ for type of stimuli and their psycholinguistic properties, known to affect the performance. We aim to identify the most appropriate naming test to be used on PPA, based on clinical and research demands.MethodWe investigated the behavioural characteristics (proportion of correct responses, error type) and the neural correlates of CaGi (Catricalà et al., 2013) and SAND (Catricalà et al., 2017) naming tests, administered to 84 healthy controls and 52 PPA (15 semantic, svPPA; 20 logopenic, lv‐PPA; 7 non fluent, nfv‐PPA; 10 mixed PPA), the latter also undergoing an FDG‐PET scan. We analyzed the ability of the tests in distinguishing PPA versus controls and between PPA variants, considering the psycholinguistic variables affecting the performance. We explored the brain metabolic correlates of the behavioural performance.ResultSAND, differently from CaGi, had response time limit and less frequent and later acquired items. A greater difficulty to name SAND items compared to CaGi ones was found. While semantic errors predominated in CaGi, both anomic and semantic errors were equally frequent in SAND. Both tests distinguished PPA from controls, but SAND outperformed CaGi in discriminating among PPA variants. FDG‐PET imaging revealed a shared metabolic involvement of the temporal areas, including the anterior fusiform gyrus, the temporal pole, and extending to the posterior fusiform gyrus in sv‐PPA, associated with lexico‐semantic processing.ConclusionA naming test with response time limits and more difficult items (as SAND) better highlights subtle distinctions between PPA variants, improving the diagnosis. Conversely, a naming test devoid of response time limits (as CaGi), may be more suited for an in‐depth characterization of the impairment and for guiding rehabilitation.