The basal ganglia inhibitory function operates in oppostive ways in the movement disorders known as Huntington's disease and Parkinson's disease. This results in unwanted or excess movements in Huntington's and slow or reduced movements in Parkinson's.
In this research, published in Brain Communications, a team from the Nuffield Department of Clinical Neurosciences led by Gwenaëlle Douaud (with Andrea Nemeth, Michele Hu and other clinical collaborators) included both Huntington's and Parkinson's early-stage patients in the same whole-brain imaging study. They used ultra-high field 7 Tesla MRI to achieve the very fine resolution needed to investigate the smallest of the basal ganglia nuclei.
Eleven of the 12 Huntington's disease carriers were recruited before showing symptoms, while 16 of the 18 Parkinson's disease patients only exhibited unilateral motor symptoms. The researchers analysed the scans of both groups as well as 24 healthy controls. The results revealed a differential effect of Huntington's and Parkinson's disease on the resting-state functional connectivity of the subthalamic nucleus within the sensorimotor network – in other words, an opposite effect compared with their respective age-matched healthy control groups.
The severity of deviation away from controls' resting-state values in the subthalamic nucleus was associated with the severity of motor and cognitive symptoms in both diseases, despite functional connectivity going in opposite directions in each disorder.
The researchers also observed an altered, opposite impact of Huntington's and Parkinson's disease on functional connectivity within the sensorimotor cortex, once again with relevant associations with clinical symptoms. The high resolution offered by the 7 Tesla scanner has thus made it possible to explore the complex interplay between the disease effects and their contribution on the subthalamic nucleus, and sensorimotor cortex.