Brain Advance Access published online on February 27, 2006
Brain, doi:10.1093/brain/awl046
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1 Department of Psychology, University of North Carolina at Chapel Hill, Chapel Hill, USA
* To whom correspondence should be addressed. Turner syndrome is a genetic disorder that results from an abnormal or missing X chromosome in females and is typically associated with impairments in visuospatial, but not verbal, information processing. These visuospatial processing impairments may be exacerbated with increased task demands, such as those engaged during working memory (WM). While previous studies have examined spatial WM function in Turner syndrome, none have directly compared the neural correlates of spatial and verbal WM processes across the encoding, maintenance and retrieval phases. We employed both neurocognitive assessments and functional MRI (fMRI) to examine the neural circuitry underlying both verbal and visuospatial WM functions in individuals with Turner syndrome and normal controls. We furthermore examined the vulnerability of task-related fMRI activation to distracters presented during WM maintenance. Fifteen healthy female volunteers and eight individuals with Turner syndrome performed a delayed-response WM task during fMRI scanning. Neurocognitive tests revealed impaired performance across both verbal and spatial domains in Turner syndrome, with greater impairment on tasks with WM demands. Frontoparietal regions in controls showed significantly sustained levels of activation during visuospatial WM. This sustained activation was significantly reduced in the group with Turner syndrome. Domain-specific activation of temporal regions, in contrast, did not differ between the two groups. Sensory distraction during the WM maintenance phase did not differentially alter frontoparietal activation between the two groups. The results reveal impaired frontoparietal circuitry recruitment during visuospatial executive processing in Turner syndrome, suggesting a significant role for the X chromosome in the development of these pathways.
Received August 26, 2005
Revised January 26, 2006
Accepted January 27, 2006
Article
Visuospatial executive function in Turner syndrome: functional MRI and neurocognitive findings
Sarah J. Hart 1,
Marsha L. Davenport 2,
Stephen R. Hooper 3,
and
Aysenil Belger 4 *
2 Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, USA
3 Clinical Center for the Study of Development and Learning, University of North Carolina at Chapel Hill, Chapel Hill, USA; Department of Psychiatry, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, USA
4 Department of Psychiatry, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, USA; Duke-UNC Brain Imaging and Analysis Center, Duke University, Durham, NC, USA
Aysenil Belger, E-mail: aysenil_belger{at}med.unc.edu
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