E04 Structure and function of the posterior cerebral cortex in huntington’s disease

Background Striatal atrophy is associated with choreatic movements in Huntington’s disease (HD). However, other symptoms of HD might be related to cortical degeneration. Thinning of the occipital lobe has been linked to visual processing deficits, but the posterior cerebral cortex has not been the primary focus of interest in previous HD research. Aims To improve the understanding of structural and functional alterations in the posterior cerebral cortex in HD using different neuroimaging modalities and visual cognitive task performance. Methods Structural and functional MRI data were acquired from 18 healthy controls, 21 premanifest, and 20 manifest HD gene carriers. Voxel-based morphometry analysis and cortical thickness measurements were performed to assess structural changes in cortical regions that are involved in visual processing. Brain function was measured by assessing neuronal connectivity in response to visual stimulation and at rest in visual resting-state networks. Multiple linear regression analyses were performed to assess associations with visuoperceptual and visuospatial function. Results Compared to controls, pronounced atrophy and decreased neuronal function at rest were present in associative visual cortices in manifest HD. The primary visual cortex did not show group differences in cortical thickness and in functional connectivity after visual stimulation. Thinning of the associative visual cortex was related to worse visuoperceptual function. Premanifest HD gene carriers did not show any differences in brain structure or function compared to controls. Conclusion This study suggests that neurodegeneration in associative visual cortices is present in early HD and is linked to clinical visual deficits, while structure and function of the primary visual cortex remains relatively preserved. Our findings can aid in the identification of other regions than the striatum that can be used as a marker of disease severity for future clinical trials.