title: Retinotopically defined primary visual cortex in Williams syndrome.
abstract: Williams syndrome, caused by a hemizygous microdeletion on chromosome 7q11.23, is characterized by severe impairment in visuospatial construction. To examine potential contributions of early visual processing to this cognitive problem, we functionally mapped the size and neuroanatomical variability of primary visual cortex (V1) in high-functioning adults with Williams syndrome and age- and IQ-matched control participants from the general population by using fMRI-based retinotopic mapping and cortical surface models generated from high-resolution structural MRI. Visual stimulation, consisting of rotating hemicircles and expanding rings, was used to retinotopically define early visual processing areas. V1 boundaries based on computed phase and field sign maps were used to calculate the functional area of V1. Neuroanatomical variability was assessed by computing overlap maps of V1 location for each group on standardized cortical surfaces, and non-parametric permutation test methods were used for statistical inference. V1 did not differ in size between groups, although its anatomical boundaries were more variable in the group with Williams syndrome. V1 overlap maps showed that the average centres of gravity for the two groups were similarly located near the fundus of the calcarine fissure, approximately 25 mm away from the most posterior aspect of the occipital lobe. In summary, our functional definition of V1 size and location indicates that recruitment of primary visual cortex is grossly normal in Williams syndrome, consistent with the notion that neural abnormalities underlying visuospatial construction arise at later stages in the visual processing hierarchy.
authors.affiliation: Section on Integrative Neuroimaging, Clinical Brain Disorders Branch, National Institute of Mental Health, NIH, DHHS, Bethesda, MD 20892-1365, USA.
authors.forename: Rosanna K
authors.initials: RK
authors.lastname: Olsen
authors.forename: J Shane
authors.initials: JS
authors.lastname: Kippenhan
authors.forename: Shruti
authors.initials: S
authors.lastname: Japee
authors.forename: Philip
authors.initials: P
authors.lastname: Kohn
authors.forename: Carolyn B
authors.initials: CB
authors.lastname: Mervis
authors.forename: Ziad S
authors.initials: ZS
authors.lastname: Saad
authors.forename: Colleen A
authors.initials: CA
authors.lastname: Morris
authors.forename: Andreas
authors.initials: A
authors.lastname: Meyer-Lindenberg
authors.forename: Karen Faith
authors.initials: KF
authors.lastname: Berman
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D003118:Color Perception; D005260:Female; D006801:Humans; D007360:Intelligence; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010364:Pattern Recognition, Visual; D010775:Photic Stimulation / Q000379:methods; D014793:Visual Cortex / Q000473:pathology / Q000503:physiopathology*; D018980:Williams Syndrome / Q000473:pathology / Q000503:physiopathology* / Q000523:psychology; D055815:Young Adult