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Impaired visual search in children with Rett syndrome.

Rose, S. A., Wass, S., Jankowski, J. J., Feldman, J. F., & Djukic, A. 2019. Pediatric Neurology

Aim: This study aims to investigate selective attention in Rett syndrome, a severely disabling neurodevelopmental disorder caused by mutations in the X-linked MECP2 gene.
Method: The sample included 28 females with Rett syndrome (RTT) and 32 age-matched typically
developing controls. We used a classic search task, in conjunction with eye-tracking technology. Each
trial included the target and several distractors. The distractors varied in number and differed from
targets in either a "single feature" (color or shape), creating a pop-out effect, or in a "conjunction of
features" (color and shape), requiring serial search. Children searched for the target in arrays containing
five or nine objects; trials ended when the target was fixated (or 4000 ms elapsed).
Results: Children with Rett syndrome had more difficulty finding the target than typically developing
children in both conditions (success rates less than 50% versus 80%) and their success rates were little
influenced by display size or age. Even when successful, children with RTT took significantly longer to
respond (392 to 574 ms longer), although saccadic latency differences were observed only in the singlefeature condition. Both groups showed the expected slowing of saccadic reaction times for larger arrays
in the conjunction-feature condition. Search failures in RTT were not related to symptom severity.
Conclusions: Our findings provide the first evidence that selective attention, the ability to focus on or
select a particular element or object in the environment, is compromised by Rett syndrome. They
reinforce the notion that gaze-based tasks hold promise for quantifying the cognitive phenotype of RTT