RAPPORTI TRA SISTEMA SEMANTICO E SISTEMA DI DESCRIZIONE STRUTTURALE: ASPETTI TEORICI, COSTRUZIONE DI UN NUOVO STRUMENTO E STUDIO DI PAZIENTI CON LESIONI CEREBRALI EMISFERICHE FOCALI

The Structural Description System stores pre-semantic visual information about the shape of objects. During visual perception, the actually perceived shape should activate the SDS before accessing the Semantic System. The standard shape of known objects results from the assembly of distinct parts, each of a given size with respect to the other parts. Also the size of the whole object in comparison to other objects may be variable, but only within a definite range. The aim of this study is to assess the knowledge of shape, features- and whole object’s dimensions, checking the influence of demographic variables. In addiction, we wanted to analyse the relationship between the knowledge of object’s shape, of whole-size and of subparts-size. To this aim we created a new neuropsychological battery which consists of 4 test based on 10 tools and 10 animals pictures from the Snodgrass set. In the Feature Dimension Assessment (FDA), the size of one feature of the picture was progressively reduced or amplified, so that only 50% of the resulting shapes was still acceptable. In the Object Dimension Assessment (ODA), two pictures were presented on the same sheet of paper, and the relative size of one of two objects was progressively reduced or amplified, so that only in 50% of the cases the relative size of the stimuli was acceptable. In addition, the battery included a picture reality judgment (FINOFI), based on real and chimerical pictures of animals and tools, and a Semantic Questionnaire (SQ) with verbal probes about perceptual and functional aspects of animals and tools. The battery was given to 100 Italian healthy participants. Each test was standardised with the Equivalent Score procedure by calculating the contribution of demographic variables. Normal control subjects’ performances were correlated to one another with Pearson’s linear correlation. The battery was also administered to 24 right brain-damaged patients and to 11 left brain-damaged patients. We used Cohen’s weighted k and McNemar test to assess the agreement between different tests in right brain-damaged patients. Right occipital patients were then picked out to verify their performance on each of the 4 tests at issue. Results show that FDA and FINOFI are apparently tapping similar aspects of the Structural Description System. ODA seems neither related to Semantic System, nor to the Structural Description System.