Sustained Attention in the Face of Distractors: A Study of Children with Rett Syndrome

Objective. The object of the present study is to advance our understanding of the cognitive profile of Rett Syndrome (RTT), an x-linked neurodevelopmental disorder caused by mutations in the MECP2 gene. We focus on sustained attention, which plays a critical role in driving cognitive growth, and use an innovative, gaze-based task that minimizes demands on the limited verbal and motor abilities associated with RTT.
Method. The task required the ability to sustain attention on a visual target (a butterfly) whilst inhibiting a prepotent response to look to moving distractors (trees and clouds) presented in the peripheral visual field. The sample included children with RTT (N = 32) and their typically developing (TD) counterparts (N = 32), aged 2-12 years.
Results. Our findings revealed that children with RTT had more difficulty sustaining attention (with the TD group averaging 60% looking at the butterfly vs only 25% for the RTT group). Furthermore, they showed that RTT was associated with difficulties in three fundamental factors influencing sustained attention: engagement, distractibility, and re-engagement. The RTT group was slower to engage, more distractible, and slower to re-engage.
Conclusion. Our findings suggest there may be a fundamental disruption to sustained attention in RTT, identifies factors related to this impairment, and points to cognitive areas that could be assessed in evaluating the usefulness of interventions.

Public Statement. Rett syndrome is an x-linked neurodevelopmental disorder characterized by a developmental regression that typically begins between 6 and 18 months, robs the child of purposeful hand use and expressive language, and results in the development of numerous medical problems. These deficits make standard neuropsychological testing becomes all but impossible, and thus little is known about their cognitive abilities. We were able to by-pass the motoric and language problems using eye-tracking technology. Here we used an innovative gaze-based task to assess sustain attention, a core driver of cognitive growth. We found that children with Rett Syndrome showed impairments in sustained attention, and on three fundamental factors influencing sustained attention: engagement, distractibility, and re-engagement. Children with Rett Syndrome were slower to engage, more distractible, and slower to re-engage than their age-matched peers. This work not only begins to elucidate the nature of the cognitive problems associated with Rett syndrome, but is essential for designing markers to assess the effects of pharmacological interventions.