By Dr. J Singh, MSc, PhD
How do we measure cognition? Typically, standardized tests which require verbal responses can be used. As a young child I had first-hand experience of these tests. My communication was severely limited and so I was exposed to a battery of tests to figure out why. In most cases my parents became frustrated about the suitability of these tests which often required a verbal response. I fondly recall during these early years that I could rationalize the entire process and even talk to nurses during assessments albeit in my head.
Capturing communication and cognitive function is challenging in children and even more so in those with significant functional disability, often seen in disorders of neurodevelopment. In the Rett community there is sometimes debate about the degree of cognitive impairment seen in our girls. The long-established view is that cognitive function is severely impaired in Rett Syndrome. Seizures are frequent in girls with Rett and although not properly evaluated for Rett Syndrome, are thought to be associated with cognitive decline . The functional impairment observed in Rett puts us in a precarious position – how can we gauge the severity of cognitive impairment in Rett Syndrome when communication in Rett girls is severely limited? As such, neuropsychological approaches used to typically assess cognitive function are not at all suitable.
Use of eye gaze as a gateway for communication in children and adults with Rett can allow for better assessment of cognitive function. Eye gaze or Eye Tracking Technology (ETT) can allow the capture of communication in this population allowing them to make informed choices . The synergy between ETT and communication responses has provided researchers with a means to monitor communicating during cognitive tasks.
Recently, an elegant study  has put these two elements together and aimed to assess cognitive function in girls with Rett Syndrome more directly using ETT. In this study, pictures were used and responses were given by ETT, and this was used as a measure of receptive vocabulary. Strikingly, the researchers found that about a third of Rett girls assessed have a level of mild cognitive impairment and some were even found to be amongst the normal cognitive range.
So where are we at? Although the study was done in a small sample of girls with Rett Syndrome (17), it adds weight to the argument that the cognitive abilities of people with Rett Syndrome might be underestimated. Once thought to be on the lower end of the cognitive spectrum, it is becoming clear that there is likely to be a range of cognitive impairment seen in people with Rett Syndrome. That said, however, if some individuals with Rett are indeed functioning at the near normal cognitive level, it suggests that strategies that incorporate educational and communication support should at the very least be re-evaluated to accommodate this.
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