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Brain Advance Access originally published online on February 27, 2006
Brain 2006 129(5):1125-1136; doi:10.1093/brain/awl046
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© The Author 2006. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org The online version of this article has been published under an open access model. Users are entitled to use, reproduce, disseminate, or display the open access version of this article for non-commercial purposes provided that: the original authorship is properly and fully attributed; the Journal and Oxford University Press are attributed as the original place of publication with the correct citation details given; if an article is subsequently reproduced or disseminated not in its entirety but only in part or as a derivative work this must be clearly indicated. For commercial re-use, please contact journals.permissions@oxfordjournals.org

Visuospatial executive function in Turner syndrome: functional MRI and neurocognitive findings

Sarah J. Hart1, Marsha L. Davenport2, Stephen R. Hooper3,4 and Aysenil Belger4,5

Departments of 1 Psychology and 2 Pediatrics, 3 Clinical Center for the Study of Development and Learning, Department of 4 Psychiatry, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill and 5 Duke-UNC Brain Imaging and Analysis Center, Duke University, Durham, NC, USA

Correspondence to: Aysenil Belger, Department of Psychiatry, CB #7160, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA E-mail: aysenil_belger{at}med.unc.edu

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.

Key Words: executive functions; fMRI; spatial working memory; Turner syndrome; verbal working memory

Abbreviations: fMRI = functional MRI; IFG = inferior frontal gyri; IPS = intraparietal sulci; ITG = inferior temporal gyri; MFG = middle frontal gyri; ROI = regions of interest; RT = reaction time; WM = working memory

Received August 26, 2005. Revised January 26, 2006. Accepted January 27, 2006.


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