Abstract
Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by a singlegene mutation, and is associated with a mild-to-moderate intellectual disability in males. Due to the well-defined neurobiological origin, FXS is frequently used as a model to study the effects of genetic abnormalities on cognitive development and behavior. A central question in this line of research is why some cognitive functions are more affected than others. To date, most studies have focused on the characterization of the higher-level cognitive processes, whereas the perceptual characteristics of information processing in the brain remain understudied. Importantly, these lower-level information processing characteristics can further our understanding of those neurobiological processes that go astray in FXS. Additionally, these investigations will reveal important information on the quality of cognitive information processing in neurodevelopmental disorders, and demonstrate that cognitive functioning in neurodevelopmental disorders cannot solely be interpreted in terms of intact vs. spared cognitive functions.
Het fragiele-X-syndroom (FXS) is een erfelijke ontwikkelingsstoornis die zowel voor bij mannen (1:4000) als bij vrouwen (1:8000) voorkomt. FXS wordt veroorzaakt door functieverlies van het fragiele- X-mentaleretardatiegen (FMR1), gelegen op het X-chromosoom, waarbij het genetische product van het FMR1-gen (FMRP) niet of te weinig wordt aangemaakt. FMRP speelt een belangrijke rol tijdens de vroege hersenontwikkeling en wordt gezien als de belangrijkste oorzaak voor de beperking in verstandelijk vermogens en gedrag bij personen met FXS (Verkerk et al., 1991). Vanwege een actief FMR1- gen op het tweede X-chromosoom zijn de beperkingen bij vrouwen vaak van mildere aard, waarbij leerproblemen en moeilijkheden in de regulatie van sociaal-emotionele vaardigheden het meest voorkomen. Bij mannen heeft de afwezigheid van FMRP grotere consequenties voor het verstandelijk functioneren en het gedrag. Het intellectuele niveau van mannen met FXS komt overeen met een matige tot ernstige verstandelijke beperking (IQ tussen de 30 en 50) en een karakteristiek gedragspatroon, waaronder hypersensitiviteit, stereotype gedragingen (handbijten en/of flapperen met de handen), sociale angst en vermijding van oogcontact (Hagerman & Hagerman, 2002).
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Molen, M.J.W. Het fragiele-X-syndroom: cognitieve vaardigheden en onderliggende problemen in de informatieverwerking. NEUROPRAXIS 16, 53–60 (2012). https://doi.org/10.1007/s12474-012-0009-1
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