Functional neuroanatomy of visuo-spatial working memory in Turner syndrome

Turner syndrome (TS), a genetic disorder characterized by the absence of an X chromosome in females, has been associated with cognitive and visuo-spat ial processing impairments. We utilized functional MRI (fMRI) to investigat e the neural substrates that underlie observed deficits in executive functi oning and visuo-spatial processing. Eleven females with TS and 14 typically developing females (ages 7-20) underwent fMRI scanning while performing 1- back and 2-back versions of a standard visuo-spatial working memory (WM) ta sk. On both tasks, TS subjects performed worse than control subjects. Compa red with controls, TS subjects showed increased activation in the left and right supramarginal gyrus (SMG) during the 1-back task and decreased activa tion in these regions during the 2-back task. In addition, decreased activa tion in the left and right dorsolateral prefrontal cortex (DLPFC) and cauda te nucleus was observed during the 2-back task in TS subjects. Activation d ifferences localized to the SMG, in the inferior parietal lobe, may reflect deficits in visuo-spatial encoding and WM storage mechanisms in TS. In add ition, deficits in the DLPFC and caudate may be related to deficits in exec utive function during WM performance. Together these findings point to defi cits in frontal-striatal and frontal-parietal circuits subserving multiple WM functions in TS.