Deficits in inhibitory executive functions in Klinefelter (47, XXY) syndrome

Klinefelter syndrome (47, XXY) is a sex chromosome aneuploidy associated with mild deficits in cognitive and language functions. Dysfunctions have also been reported in performance of tasks which examine executive functions. However, it is unclear whether the impaired performance is caused or accentuated by problems with semantic processing and information processing speed. In the present study we used an experimental task which is relatively insensitive to these confounding factors. We examined inhibitory executive functions in a group of XXY males compared with male (XY) and female (XX) controls, using a dichotic listening speech sound task with instructions to focus attention on either the right or the left ear stimulus. With this task, inhibitory executive functions can be assessed separately from language, processing speed, and attention orientation abilities. We found that XXY males showed a selective deficit in inhibitory executive functions compared to both control groups, whereas attentional orientation was not impaired. The present findings suggest that executive dysfunctions associated to Klinefelter syndrome can be selectively identified, and are particularly accentuated in the inhibitory sub-component. Such improved understanding of the nature of executive dysfunctions in XXY males may aid the development of specific neuropsychological rehabilitation strategies.