Measures of Attention in Rett Syndrome: Internal Consistency Reliability

Objective: Rett syndrome (RTT), an x-linked neurodevelopmental disorder caused by spontaneous mutations in the MECP2 gene, is characterized by profound impairments in expressive language and purposeful hand use. We have pioneered the use of gaze-based tasks to by-pass these limitations and developed measures suitable for clinical trials with RTT. Here we estimated internal consistency reliability for three aspects of attention that are key to cognitive growth and that we previously identified as impaired in RTT. Method: Using a sample of 66 children with RTT (2–19 years), we assessed Sustained Attention (butterfly task: Butterfly traverses the screen only when fixated and distractors are ignored); Disengaging/ Shifting Attention (“gap/overlap” task: Shifts of gaze from central to peripheral targets are compared in conditions where the central stimulus remains or disappears at the onset of the peripheral target); Selective Attention (search task: the target is embedded in arrays differing in size and distractor type). Results: Reliability was acceptable to excellent on almost all key measures from tasks assessing Sustained Attention and Disengaging/Shifting Attention, with split-half coefficients and Cronbach alphas ranging from.70 to.93. Reliability increased as more trials were aggregated, with acceptable levels often reached with as few as six to nine trials. Measures from Selective Attention showed only limited reliability. Conclusion: Finding that critical aspects of attention can be reliably assessed in RTT with gaze-based tasks constitutes a major advance in the development of cognitive measures appropriate for clinical and translational work.