Functional Connectivity During Auditory Processing in Huntington’s Disease

Abstract

Huntington’s disease (HD) is a neurogenetic disorder accompanied by structural alterations of the basal ganglia. In a recent study we investigated auditory processing in symptomatic and presymptomatic HD. Increased activation intensities were found for the symptomatic-HD group compared to controls, which were assumed to reflect an ability to maintain functioning. However, altered functional connectivities may also give this appearance. In this study we evaluated (1) if functional connections and, hence, the organization between brain areas is also altered and (2) how intensity of activation in a brain region relates to functional connectivities of that brain region. Functional connectivity analysis was applied to the data, including the Heschl gyrus, mediodorsal thalamic nucleus, caudate nucleus, putamen, and, as a control, a region of interest (ROI) in the occipital cortex. The symptomatic group presented higher functional connectivity than the pre-HD and control groups between thalamic nuclei bilaterally, and between the left caudate and left thalamic nucleus, respectively. The pre-HD group showed no altered patterns of functional connectivity compared to controls. Moreover, functional connectivity was inversely related to activation intensity of the corresponding brain region. The results suggest that alterations in functional connectivity in HD possibly relate to the degree of neuropathology and are sensitive to hemisphere-dependent differences in neuropathology. The inverse relation of functional connectivity and activation intensity suggests that they may alternative strategies that can be used to maintain brain function in the neurodegenerative advanced stage in HD patients. Since functional connectivity was not altered until the symptomatic stage, the results indicate that functional connectivity is a robust measure, since it does not alter until late stages of disease, when neuropathology becomes more severe.