[Functioning of memory in subjects with autism]

Abstract

Introduction: Autism is an early developmental disorder with cognitive impairments that leads to learning and social integration disabilities. The characterization of memory functions in individuals with autism has been the subject of numerous investigations, with widely varying conclusions. The notable differences between these studies can be attributed to variations in the age, intelligence and level of severity of the participants with autism.

Literature findings: The purpose of our review of the recent literature is to describe the memory function of individuals with autism. Some of the different memory subtypes are intact, others are impaired. Short-term memory (digit span) is not impaired while working memory is impaired in some of its components, but the findings are inconsistent. More recent studies demonstrate reduced spatial working memory abilities in autism and extend previous findings by demonstrating that these deficits are significant when tasks impose heavier demands on working memory. Episodic long-term memory, as measured by free recall, cued recall or recognition tasks, is intact, but participants with autism perform significantly less well than controls as the complexity of the verbal or visual material to be recalled increases. Source or contextual memory involves a variety of characteristics specifying the conditions under which specific items or facts are acquired: it has been investigated in individuals with autism with different methods. Deficits in source memory for temporal information have been found, but there were no reality monitoring deficits. Recent findings indicate that the nature of source memory confusion in autism does not appear to reflect a generalized deficit in attaching context to memories, but rather is dependant on the specific to-be-remembered information that involves social aspects of context. The self-reference effect is missing, with individuals with autism recalling events performed by themselves less well than the events performed by a peer, suggesting they have difficulties in relation to processes involving the self. Studies involving assessment of subjective states of awareness during recognition show less conscious recollection and more feelings of familiarity. Recent investigations are consistent in demonstrating memory impairments related to the failure of subjects with autism to use organizing strategies or meaning to support memory, an effect which grows with the increasing complexity of the material. Memory deficits in autism may be related more to retrieval and less to encoding, as deficit in source memory in participants with autism is largely eliminated when source was supported at test.

Discussion: The neuroanatomical basis of the specificities of memory impairment in autism is still uncertain, but it is suggested that autism involves an impairment in the conversion of limbic inputs into medial prefrontal outputs. Memory deficits found in individuals with autism may explain some of the clinical symptoms. Failure to encode all the information, especially its social aspects, may therefore contribute to dysfunction in the social, communication, and reasoning domains. Abnormal memory functioning in autism is also related to more general cognitive impairments, including executive function deficits and central coherence weakness. Evidence of the normality of certain memory capacities, at least in individuals with moderate autistic symptomatology, is encouraging for adaptive improvements in cognitive functioning.