Analysis of Cortical Biomarkers for PD

Overview

Previous studies revealed changes in the pattern of cortical electrical activity of patients with Parkinson's disease (PD) and suggested that these changes may be dependent on the phenotypes of the disease and other related factors. A greater understanding of cortical electrical activity in PD patients may be relevant to guide professionals about the therapeutic use of repetitive transcranial magnetic stimulation (rTMS). The present study aims to evaluate the pattern of brain activity of PD patients and to correlate the findings with the disease phenotypes and with other clinical characteristics. For this, volunteers with PD and healthy will participate in a single experimental session in which behavioral and electrophysiological assessments will be performed.

Healthy individuals, after reading and signing the free and informed consent will be submitted to a single session to obtain the normal neurophysiological and behavioral endpoints and thus compare with those obtained in individuals with PD. All volunteers (healthy and patients) will be submitted to a behavioral and neurophysiological evaluation through transcranial magnetic stimulation (TMS) and electroencephalography (EEG). The neurophysiological evaluation will be conducted during "ON" (with medication) and "OFF" (without medication) period, by transcranial magnetic stimulation by single pulse (EMT-p) and by EEG. TMS can perform different measures for the study of cortical excitability. The analysis of the motor cortex excitability will be held by: (i) determination of motor threshold (ii) the amplitude of the motor evoked potential (MEP). Since the assessment of the cortex activity will be held by: (i) power spectrum density (PSD) of all frequencies bands.75 For evaluation with the TMS (Neurosoft - Russia) volunteers will be instructed to sit in a chair and get comfortable position. Initially single TMS stimuli will be administered over the motor cortex to determine the cortical representation area of the first dorsal interosseous muscle (FDI) - MEP region whose response occurs more intensely observed by electromyography. The electrodes with 10 mm diameter should be placed on the belly of the target muscle and the reference electrode is placed in the interphalangeal joint of the thumb. All care for the acquisition of electromyographic signal will be taken according to the criteria of Surface Electromyography for the Non-invasive Assessment of Muscles (SENIAM). For the location of the representative FDI muscle cortical region coil with an angle of 45 degrees is positioned at a distance of 20% of Cz point (according to the international system for marking 10-20) bring into the contralateral muscle to be evaluated. For all evaluations the same coil is used, the figure-eight angled in order to avoid measurement bias. To assess cortical excitability of both hemispheres, the following measures are carried out: resting motor threshold (RMT) and motor evoked potentials (MEP). For EEG assessment, the electrodes will be positioned on the scalp of the individual, according to the international 10-20 marking system, maintained with the maximum impedance of 10kΩ. During the acquisition of the electroencephalographic signal, a motor imagery and execution protocol will be performed, in both upper limbs. The collected data will be further processed and analyzed by MATLAB® software for Windows. For behavioral assessment the following scales and tests will be performed during "ON" (with medication) and "OFF" (without medication) period: Parkinson's disease sleep scale; Geriatric Depression Scale; Edinburgh Handedness Inventory; International Physical Activity Questionnaire; Timed up and go test; Berg Balance Scale; Unified Parkinson's disease Rating Scale sessions II and III.