Cognition spatiale chez les personnes atteintes de Trisomie 21 et du syndrome de Williams

Down syndrome (DS) and Williams syndrome (WS) are two genetic neurodevelopmental disorders generally characterized by moderate to severe intellectual disabilities. However, individuals with DS and WS exhibit unique patterns of brain development, which result in unique cognitive profiles. For example, persons with WS exhibit severe visuo-spatial memory deficits, which are believed to result from neuroanatomical abnormalities in the dorsal visual stream including the posterior parietal cortex. In contrast, persons with DS show relatively preserved visuo-spatial memory, but are more impaired in visual-object memory, resulting from greater abnormalities in the ventral visual stream. Abnormalities in the hippocampal formation of both individuals with DS and WS have also been identified. Whereas the majority of studies investigating the cognitive profiles manifest in these two neurodevelopment disorders have assessed spatial memory using classical neuropsychological “tabletop” tests, studies of the real-world spatial and navigational abilities of these populations are notably lacking. In a real-world, individuals move around in their environment, and thus have access to all sensory information necessary to create coherent and efficient allocentric spatial representations. Importantly, allocentric spatial memory is a fundamental component of episodic memory and depends on the integrity and function of the hippocampal formation. Although a few studies have assessed spatial processing in large-scale environments with WS individuals, none have actually addressed the question as to whether allocentric spatial capacities, specifically, can be considered as preserved in the WS or DS profile. Such information will not only enable us to better understand brain-function relationships in these disorders, but will also allow cognitive therapists to design alternative strategies for solving every day spatial problems in the lives of these persons.