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Attentional shifting and disengagement in Rett syndrome.

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

Objective. The purpose of the present study was to deepen our understanding of attention (a core cognitive ability) in Rett syndrome (RTT), an x-linked neurodevelopmental disorder caused by mutations in the MECP2 gene. We focused on two key aspects of visual orienting--shifting and disengaging attention--both of which are critical for exploring the visual world. We used gaze-based measures and eye-tracking technology to minimize demands on the limited verbal and motor abilities associated with RTT. Method. Shifting and disengaging attention were examined in 31 children (2-12 years) with Rett Syndrome (RTT) and 31 age-matched typically-developing (TD) controls. Using the gap-overlap paradigm, the frequency/speed of shifting attention from a central to peripheral target were compared on Baseline trials, where the central stimulus disappears as the peripheral target appears, and Overlap trials, where the central stimulus remains, thus requiring disengagement. Results. Our findings revealed that children with RTT had more ‘sticky fixations’(p<.001). That is, they had fewer saccades to the peripheral target than TD children, and this was true on both baseline (77% vs 95%), and overlap trials (63% vs 90%); the younger ones also had slower saccadic reaction times (SRTs)(p=.04). Within the RTT group, SRTs correlated with symptom severity. Surprisingly, disengagement cost (the relative difference between gap and overlap SRTs) did not differ across groups. Conclusion. Our results suggest that children with Rett have difficulty shifting attention and, to a lesser extent, disengaging attention, whereas with other disorders, problems with disengagement are paramount.

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

Sustained attention in the face of distractors: A study of children with Rett syndrome

Rose, S. A., Wass, S., Jankowski, J. J., Feldman, J. F., & Djukic, A. 2017. Neuropsychology

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.