Dual Attention Abnormalities in Children with Autism

Background: Although autism and attention deficit/hyperactivity disorder (ADHD) represent different nosological diagnoses they partly include similar symptoms like hyperactivity, impulsivity that are hypothetically linked to  impairments in executive attention control. The specificity of the executive control disturbances in ADHD and higher functioning autism (HFA) is poorly understood.

Objectives: To determine the sort and degree of deficiency in executive attention profile in ADHD, HFA comparing to typically developing boys (TDB). Methods: 15 boys with HFA aged 6-7 years were compared with 15 IQ-matched TDB and 15 IQ-matched boys with ADHD. To delineate more specifically the efficiency of different executive attention operations (control of interference; dividing attention between visual and auditory sensory modalities; set-shifting) we have developed the child test of executive attention (TEA). Repeated measures ANOVA was used for analysis of reaction time, percentage accuracy and false alarms.

Results: Unlike the ADHD who demonstrated the specific difficulty in controlling attention under the tasks tapping control of interference, children with HFA performed worse than ADHD and TDB in all tasks requiring continuous visual attention with no particular deficit in executive attention tasks. This suggest the decreased efficiency of  alerting system in autism, which is involved in maintaining readiness to react. The second feature of HFA, which strikingly differentiate them from both TDB and ADHD, was the abnormally poor reaction (in terms of RT and percent accuracy) to auditory target but not to  visual target when they were presented in alternating fashion (dual attention task). Their reaction to isolated sound presentation did not differentiate them from two other groups.

Conclusions: Children with autism and ADHD showed different profile of attention impairment. The disturbed tonic alerting system and unresponsivness to sound due to attention switching abnormalities may  be specific to autism and unrelated to deficits in frontal functions.