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Williams syndrome: neuronal size and neuronal-packing density in primary visual cortex
Albert M Galaburda1, Dorothy P Holinger, Ursula Bellugi
1Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA 02215, USA. agalabur@caregroup.harvard.edu
Archives of Neurology
|September 12, 2002
Summary
Williams syndrome (WMS) brains show altered peripheral visual cortex cell packing and size, particularly in the left hemisphere. These neuroanatomical differences may explain visuospatial deficits in individuals with WMS.
Area of Science:
- Neuroscience
- Genetics
- Developmental Biology
Background:
- Williams syndrome (WMS) is a rare genetic disorder caused by a 7q11.22-23 hemideletion.
- WMS is characterized by distinct cognitive and behavioral features, including visuospatial deficits and preserved language.
- A neuroanatomical hypothesis suggests dorsal hemisphere and peripheral visual field involvement in WMS.
Purpose of the Study:
- To investigate neuroanatomical differences in the primary visual cortex (area 17) between WMS-affected and control brains.
- To examine cell-packing density, neuronal size, and size distribution in specific cortical layers.
Main Methods:
- Autopsy specimens from 3 WMS brains and 3 age/sex-matched controls were analyzed.
- The optical dissector method was used to measure neurons in layers II, III, IVA, IVB, IVCalpha, IVCbeta, V, and VI.
- Comparisons were made for cell-packing density and neuronal size between WMS and control groups.
Main Results:
- Abnormalities were observed in the peripheral visual cortex of WMS brains, but not in magnocellular pathways.
- A significant hemisphere by layer IV interaction and a layer IV left hemisphere and diagnosis interaction were found for cell-packing density.
- WMS brains exhibited increased cell-packing density in left sublayer IVCbeta and an excess of small neurons in left layers IVA, IVCalpha, IVCbeta, V, and VI.
Conclusions:
- Cell measurements in peripheral visual cortical fields differ in WMS, with smaller, denser cells in some left-sided layers.
- These findings suggest that altered cell-packing density and neuronal size in the visual cortex may contribute to visuospatial deficits in WMS.