Computerized Open-Source Navon Test (COSNaT): Normative data for the assessment of global processing abilities and simultanagnosia in the Italian population

Disorders in global processing abilities may be evident when posterior cortical regions are damaged due to a focal brain lesion or neurodegenerative diseases, such as posterior cortical atrophy (PCA). While in severe cases global processing deficits are evident as simultanagnosia, subtle impairments may be present early, as in patients with multi-domain mild cognitive impairment (MCI). The aim of the present study is to provide norms for the Computerized Open-Source Navon Test (COSNaT), which has already been validated in clinical populations. After a baseline that requires identifying large and small standard letters, the test measures the ability to identify the global and local levels of incongruent Navon's hierarchical letters. A total of 200 neurologically unimpaired participants (113 F, 56.5%) with a mean age of 57.2 years (range 20-90) and a mean education of 14.1 years (range 5-28) took part in the study. The influence of demographic variables (age, education, sex) on participants' performance was evaluated using measures of errors and response times (global, local, and delta global/local). Raw scores, regression-based adjustments for age and education levels, and equivalent scores were provided for each index. The present study provides norms in the Italian population for the COSNaT, which has been shown to be sensitive in detecting global processing impairments and simultanagnosia in different clinical populations (PCA, amnestic MCI). The computerized test may contribute to a more accurate clinical characterization of the neuropsychological profile of patients with different etiologies, as well as in prodromal stages of neurodegenerative diseases.