Aberrant frontostriatal connectivity in Alzheimer's disease with positive palmomental reflex

Background and purposePrimitive reflexes may reoccur in various neurodegenerative diseases. However, little is known about their structural and functional correlates in the human brain. Notably, the neural mechanisms underlying a positive palmomental reflex (PMR) are poorly understood. As recent studies link Alzheimer's disease (AD)‐related primitive reflexes to a dysfunction of the corticostriatal motor circuit (CMC), we conducted the present study to investigate functional and structural correlates of a positive PMR. We hypothesized an involvement of frontostriatal structures and an impairment of the CMC.MethodsUsing whole‐brain resting‐state functional connectivity (FC), hypothesis and FC result‐based probabilistic tractography, and voxel‐based morphometry analyses, we compared two groups of AD patients with either positive (n = 12) or negative PMR (n = 12).ResultsNo significant differences in grey matter volume or structural connectivity (SC) could be observed between the PMR‐positive and PMR‐negative groups. In contrast, the PMR‐positive group showed a decreased seed‐to‐voxel FC between the bilateral supplementary motor area and parts of the right‐hemispherical caudate nucleus and thalamus and a decreased region of interest (ROI)‐to‐ROI FC between the left putamen and the left superior frontal gyrus.ConclusionData suggest that dysfunction of the CMC reflected by decreased FC underlies a positive PMR in patients with AD. The lack of significant grey matter or SC differences might reflect that changes in FC appear before changes in SC in the structures of the CMC and brain atrophy

The impact of subthalamic deep brain stimulation on belief revision and social validation

We investigated whether Deep Brain Stimulation (DBS) of the subthalamic nucleus (STN) influences social validation as measured by a Judge-Advisor task. In contrast to healthy controls and patients with their DBS OFF, patients with their stimulation switched on do not experience a gain of confidence after receiving competent advice