Effects of personalized transcranial alternating current stimulation associated with physical therapy on motor and cognitive functions in people with Parkinson's disease

Abstract

Hypersynchronization of oscillatory brain activity, prevalent in the beta band, is a neurophysiological signature of Parkinson's disease (PD). Transcranial alternating current stimulation (tACS) can entrain cortical activity at the stimulation frequency. The aim of this study was to provide a personalized neurostimulation treatment associated with physical therapy to improve motor and cognitive functions in PD. Seventeen persons with PD were recruited. Fourteen concluded the protocol (2 changes of diagnosis, 1 refusal to continue). A resting state EEG was acquired and analyzed with Fast Fourier Transform to obtain power spectral density maps. Comparison of a control group versus each patient was performed using a z-test. Statistical maps provided site and frequency of stimulation (stimulation frequency was set at 30 Hz in theta prevailing group and at 4 Hz in beta prevailing group). Stimulation site was identified as the scalp area in which the prevailing band was more represented. The experiment consisted of two-weeks sessions of randomized real tACS or transcranial random noise stimulation (sham) followed by a 1-hour physiotherapy session. EEG and clinical assessments with Unified Parkinson Disease Rating Scale (UPDRS-III) and a neuropsychological battery were performed before stimulation (T 0 ), after stimulation (T 1 ) and 4 weeks follow-up (T 2 ). Ten subjects showed a prevailing beta band and 4 a prevailing theta. A reduction of beta rhythm emerged at T 1 over the bilateral sensorimotor and right frontal area and at T 2 over the left frontal area in the real group. No significant modulation of EEG activity emerged in theta prevailing group. UPDRS-III scores improved at T 1 and T 2 in the real group. A score reduction emerged at T 1 in both groups for Beck Depression Inventory and at T 2 in the real group for Geriatric Depression Scale. Personalized tACS appears a valid add-on treatment for motor dysfunction and depressive symptoms in PD.