Plantar stimulation alters brain connectivity in idiopathic Parkinson's disease

Objective Individuals with Parkinson's disease (PD) and freezing of gait (FOG) present peripheral and central sensitivity disturbances that impair motor performance. This study aimed to investigate long-term effects of plantar sensory stimulation on brain activity, brain connectivity, and gait velocity of individuals with PD and FOG. Methods Twenty-five participants were enrolled in this clinical trial (NCT02594540). Plantar sensory stimulation was delivered using the Automated Mechanical Peripheral Stimulation therapy (AMPS). Volunteers were randomly assigned to real or placebo AMPS groups and received eight sessions of treatment. The primary outcome was brain activity (task-based fMRI-active ankle dorsi-plantar flexion). Secondary outcomes were brain connectivity (resting state-RS fMRI) and gait velocity. fMRI was investigated on the left, right, and mid-sensory motor regions, left and right basal ganglia. Results No changes in brain activity were observed when task-based fMRI was analyzed. After real AMPS, RS functional connectivity between basal ganglia and sensory-related brain areas increased (insular and somatosensory cortices). Gait velocity also increased after real AMPS. A positive correlation was found between gait velocity and the increased connectivity between sensory, motor and supplementary motor cortices. Conclusion Plantar sensory stimulation through AMPS was not able to modify brain activity. AMPS increased the RS brain connectivity mainly in areas related to sensory processing and sensorimotor integration. Plantar stimulation could be a way to improve plantar sensitivity and consequently ameliorate gait performance. However, the mechanisms behind the way AMPS influences brain pathways are still not completely known.