Effects of Repetitive Transcranial Magnetic Stimulation on Two Cerebellar Targets

Effects of Repetitive Transcranial Magnetic Stimulation (rTMS) on Two Cerebellar Targets (Lobule VIII vs. CRUS I/II)

The purpose of this study is to understand how different areas of the cerebellum (a part of the brain) control different functions and how they can be influenced by non-invasive brain stimulation.

While researchers know that repetitive Transcranial Magnetic Stimulation (rTMS) can have positive effects on conditions like stroke and schizophrenia, they do not yet fully understand which specific stimulation settings work best or which exact parts of the cerebellum should be targeted for different symptoms.

This study compares the effects of stimulation on two specific regions:

• Lobule VIII: Linked to movement and motor learning.
• CRUS I/II: Linked to attention, thinking (cognition), and predicting the timing of events.By comparing these areas, researchers hope to gain the information needed to develop better treatments for neurological and psychiatric disorders.

This is a randomized, double-blind study involving 40 healthy volunteers. Participants will be split into two groups:

• Group 1: Receives "exciting" (activity-increasing) stimulation.
• Group 2: Receives "inhibiting" (activity-decreasing) stimulation.

Each participant will attend three different test sessions in a random order:

• rTMS targeting Lobule VIII
• rTMS targeting CRUS I/II
• Placebo (Sham) stimulation that looks and feels like the real thing but does not affect the brain.

During each session, researchers will use brain imaging (fMRI) and computerized tasks to measure changes in brain connectivity and performance in motor and cognitive activities.

There is no direct medical benefit to the participants. However, the results will help scientists create better therapies for patients with brain-related health issues The risks are considered minimal. Common side effects of rTMS include temporary mild headaches or a clicking sound during stimulation. MRI scans can sometimes cause mild discomfort or a feeling of closed-in spaces (claustrophobia). Researchers have put safety measures in place, such as hearing protection and constant medical supervision during scans, to minimize these risks.

Inclusion Criteria:

• Subject, male or female, aged between 18 and 60 years inclusive
• Subject affiliated with or a beneficiary of a social security health insurance scheme
• Subject has dated and signed the informed consent form prior to the start of any trial-related procedures
• For women of childbearing potential, a negative urinary pregnancy test and the use of effective contraception throughout the duration of the study

Exclusion Criteria:

• Subject with substance use disorders (as defined by the DSM-5)
• Subject having taken benzodiazepines and related compounds (within the period preceding inclusion, for a duration equivalent to 5 half-lives of the product), cannabis (within the 2 months preceding inclusion), or hallucinogenic substances (within the period preceding inclusion, for a duration equivalent to 5 half-lives of the product)
• Subject suffering from a neurological pathology or sequelae
• Subject with Attention-Deficit/Hyperactivity Disorder (ADHD)
• Subject with Borderline Personality Disorder
• Subject presenting with disabling sensory impairments, specifically a visual acuity (corrected, if applicable) < 0.8 (due to the use of visual materials; Freiburg Vision Test, Bach 1996; verified during an examination at the screening visit)
• Subject deprived of liberty or under legal protection
• Subject under guardianship or trusteeship
• Pregnant or breastfeeding woman (verified by a urinary test at the screening visit)
• Subject within an exclusion period defined by another clinical study or participating in a study likely to impact the results of the research
• Subject presenting a contraindication for fMRI or rTMS: presence of non-removable ferromagnetic bodies, prostheses, pacemakers, implanted medication pumps, vascular clips or stents, heart valves or ventricular shunts, certain intracerebral clips, cochlear implants, history of seizures (epilepsy), or skin breach/pathology at the point of contact with the electrodes
• Subject with a history of major neurological or psychiatric disease with current psychotropic medication (i.e., antipsychotics, benzodiazepines and related compounds, or hypnotics)