Memory development and intellectual disabilities.

Neuropsychological research has permitted different cognitive profiles among subjects with intellectual disabilities (ID) of different etiology to be defined. For example, numerous authors have stressed that the typical language profile for people with Down's syndrome (DS) consists of poor production with greater compromise of morphosyntax than of lexical abilities, but relatively preserved comprehension. Children with Williams' syndrome (WS) often show marked impairment in certain visuospatial abilities (especially praxic-constructive) and relative preservation of both productive and receptive language, at least concerning the phonological elements. These observations seem to support a theoretical approach that considers ID not as a mere slowing of normal cognitive development, but as distinct, individual profiles that can be qualitatively specified. The importance of this approach was shown in several recent studies of memory, especially implicit memory in subjects with ID. Neuropsychological studies suggest insufficient development of the mnemic function in ID at different levels of articulation. Long-term memory has been extensively investigated in people with ID both in the explicit and in the implicit component. According to recent studies, people with ID should show a diffuse impairment of declarative mnesic abilities and a relative preservation of implicit memory. The focus of this study is on the characteristics of long- and short-term memory in children with ID and, particularly, with DS and WS. The results are relevant to knowledge on the qualitative aspects of the anomalous cognitive development in mentally retarded people and the neurobiological substrate underlying this development.