Autism spectrum disorders. Developmental, cognitive and neuropsychological aspects

Abstract

Introduction and aims: Autism, Asperger syndrome and attention-deficit/hyperactivity disorder (AD/HD) are clinically defined neuropsychiatric syndromes that affect 6 to 10 per cent of all children. These common developmental disorders can be understood at different levels. This thesis highlights neurocognitive functions as they relate to the understanding of autism spectrum disorders, the stability of these functions over time and the influence of gender on the expression of such disorders. A secondary aim of the study has been to propose relevant methods for neuropsychological clinical assessment.Subjects and methods: The majority of the 292 children included in the studies were drawn from the register of or clinical projects performed at the Child Neuropsychiatry Clinic in Göteborg. In most cases, the age range (6-12 years) of the children included, was restricted to a period of growth of logical thinking (the stage of Piaget´s "concrete operations"). and so called of executive functions. The work made use of a broad spectrum of assessment methods tapping into various neurocognitive abilities, including developmental level, intelligence, perception, executive functions, "central coherence" and "theory of mind".Results and preliminary discussion: Children with developmental disorders, except most of those with Asperger syndrome showed a general cognitive impairment as reflected in lower IQ. All diagnostic groups also showed uneven cognitive profiles (in the cases of autism already in the early pre-school years), with peaks and troughs affecting cognitive processing in different ways. All clinic children - regardless of diagnostic category - were impaired in respect of executive functions. When measures were divided into Mirsky´s four components of attention, all groups showed deficits involving "sustain", "focus-execute" and "encode" attention. The AD/HD group showed the most pervasive difficulties and was affected also in the "shift" component of attention. The results suggest that executive functions may be relatively independent of cognition and other neuropsychological abilities. The stability of cognitive and executive functions over time were strong enough to suggest that re-evaluation within a 1-2-year interval would add little new information. Relatively high-functioning clinic girls with neuropsychiatric disorder seemed to be slightly more neurocognitively impaired than corresponding clinic boys. Practical implications for neuropsychological assessments are discussed as are different neurocognitive functions and their relationship to each other.Conclusions: Combining a behavioural/phenomenological approach - such as currently represented by the DSM-IV - with tests of neuropsychological abilities might contribute to a better understanding of the underlying impairments and provide implications for special education interventions. The neuropsychological test results showed a high degree of stability over time. The tendency for girls with neuropsychiatric disorder to be more impaired than boys on neuropsychological tests, needs to be examined in new and larger samples.