Study Evaluating the Effect of Transcranial Direct Current Stimulation (tDCS) Targeting the Right Inferior Frontal Gyrus on Inhibitory Control in Patients With PSP

Progressive supranuclear palsy (PSP) is a rare neurodegenerative disease with a prevalence estimated at 6 per 100,000 in France and a rapidly progressive course. In its classic form (known as the Richardson type), it presents with a predominantly axial Parkinsonian syndrome, postural instability with early falls, oculomotor disorders, and cognitive and behavioral disturbances. Apart from levodopa, which may provide a modest improvement in Parkinsonian syndrome in some patients, the current therapeutic approach relies primarily on rehabilitation techniques, with no proven efficacy. Cognitive-behavioral symptoms are common in this disease and are primarily characterized by impaired executive functions, linked to dysfunction of the frontal cortex. They often have a devastating effect on quality of life, are associated with an increased risk of falls, and represent a considerable burden for caregivers. Among these symptoms, apathy is the most commonly described symptom. Impulsivity, associated with impaired inhibitory control, is present in 32-74% of cases and may coexist with apathy. Cognitive and behavioral inhibition depends on a complex brain network that includes, among others, the right inferior frontal gyrus (IFG), the dorsolateral prefrontal cortex, the supplementary motor area, the motor cortex, and the basal ganglia. It has recently been shown that patients with PSP have impaired functional connectivity between the right LFC and other brain structures in the network, and that neurotransmitter deficits in the right LFC correlate with their impulsivity Alongside pharmacological approaches, non-invasive brain stimulation techniques are rapidly expanding as a potential therapeutic tool. Transcranial direct current stimulation (tDCS), by modulating cortical excitability, is a promising technique. It is simple to administer and has demonstrated efficacy in several clinical settings. Furthermore, a recent meta-analysis of 45 clinical studies shows that single or r