Among the factors contributing to this variability, those occurring in the perinatal period (starting with the 20th or 28th week of gestation through the 1st or 4th week after birth) may be of special importance because this is a period of great vulnerability for the developing brain 24.ĭrawing on studies in the euploid population, the association between perinatal events and long-term cognition is well established 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35. In addition, certain comorbidities associated with trisomy 21 (i.e., congenital heart defects, sleep disorders, low thyroid function) are also thought to contribute to this variability 19, 20, 21, 22, 23. In this regard, previous investigations have suggested that differences in genetic 14, 15, 16 and environmental factors 17, 18 between individuals with DS are related to the degree of impairment in specific cognitive and behavioral areas. Understanding which factors contribute to the observed within-syndrome variability is crucial, and one of the main challenges to an etiology-specific approach to intervention for those with DS 13. ![]() Several other studies have shown that other cognitive areas, such as executive function, attention, and language are also quite variable across individuals with DS 5, 9, 10, 11, 12. However, it is important to note that the cognitive phenotype described above is variable across individuals with DS 7.įor example, one study reported that standard deviations for implicit memory scores were almost three times larger in a group of individuals with DS compared with a cognitive-level matched group of TD individuals indeed, some individuals with DS even outperformed TD controls 8. This profile is characterized by a general cognitive delay, relative strengths in nonverbal abilities, and impairments beyond mental age expectances in language, phonological processing, verbal memory and verbal working memory 2, 3, 4, 5, 6. Although the DS phenotypic features are variable, when compared either to typical developing (TD) controls or to other neurodevelopmental disorders (NDDs), a distinctive cognitive profile is generally observed. DS is a complex condition that affects both physical and cognitive development. Down syndrome (DS) is the most common known genetic cause of intellectual disability (ID) and results from an extra copy of all or part of chromosome 21 1.
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