Clinical and Neurophysiological Effects of tDCS on Depression in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder, characterized by dopaminergic cell degeneration leading to neurophysiological alterations and a heterogeneous clinical presentation. In addition to motor symptoms, PD patients often experience non-motor symptoms, particularly neuropsychiatric manifestations such as depression, anxiety, and apathy. Depression is one of the most prevalent behavioral symptoms, affecting at least 50% of PD patients, with a higher incidence compared to the general population and other disabling conditions. Two main hypotheses explain the emergence of depressive symptoms: one considers depression a reactive response to progressive disability, while the other links it to the underlying neurobiological mechanisms of PD. Additionally, depression and anxiety frequently co-occur in PD, suggesting shared neurobiological pathways. Conventional pharmacological treatments only partially address affective symptoms in PD, highlighting the need for innovative non-pharmacological therapies. Transcranial direct current stimulation (tDCS) has gained attention as a potential treatment, showing promising results in improving both motor and affective symptoms in PD. While preliminary studies suggest that tDCS may significantly reduce depressive symptoms, current evidence is insufficient to establish clinical recommendations, necessitating further large-scale, randomized controlled trials. Objectives The primary objective of this study is to evaluate the effects of repeated tDCS sessions on depressive symptoms in PD patients. Secondary objectives include: * Assessing the potential impact of repeated tDCS sessions on anxiety, apathy, sleep quality, and quality of life in PD patients. * Investigating the neurophysiological mechanisms underlying depression and the effects induced by tDCS. Methodology Eligible patients will be randomly assigned to one of two groups: 1. Experimental Group: Patients will receive repeated session