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

Abstract

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.

Brain sex matters: Estrogen in cognition and Alzheimer’s disease

“…The sex hormone-dependency of brain regional development has been further supported by the study in girls with partial or complete loss of their X-chromosome, which showed disproportionately reduced hippocampal volume, and increased amygdala volume relative to age-matched controls [91]. The estrogen-related brain regional volume reduction in females with endogenous estrogen deficiency is further evidenced by the impairment of executive performance on the task as reported by other groups of researchers [92]. In animal studies, female mice exposed to stress in early adolescence showed more disturbed sexual behaviors than those exposed to stress in late adolescence, emphasizing the importance of timing of exposure even within adolescence [93].…”

Estrogen and hearing from a clinical point of view; characteristics of auditory function in women with Turner syndrome

“…They report changes in the left parieto-occipital region extending into the frontal lobe and bilaterally in the internal capsule extending into the globus pallidus and in the right prefrontal region. Studies on visuo-spatial working memory in Turner females showed reduced sustained activation in fronto-parietal regions on fMRI compared to controls (Hart et al, 2006).…”

Genomic Imprinting Effects on Cognitive and Social Abilities in Prepubertal Girls with Turner Syndrome

“…It is interesting that other measures tapping individual executive functions (NEPSY attention/executive domain) and visuospatial skills (MVPT-3, WRAVMA) did not differ between groups. It is plausible that X pat individuals may be more vulnerable than X mat when it comes to recruiting additional cognitive resources needed to face challenging visuospatial problems, a phenomenon that has been previously documented in TS (15,16).…”