Improving Obsessive-compulsive Disorder Treatments: from Lesions to Neuromodulation Targets

Transcranial Magnetic Stimulation (TMS) involves generating a magnetic field with specific spatial and temporal properties, allowing the induction of electric current in conductive material near this field. The electro-physiological principle of TMS is based on placing a coil over the skull that will induce a magnetic field generating action potentials in neuronal tissue in response to each TMS pulse. The repetitive application of TMS pulses (rTMS) allows for the modulation of neuronal excitability for a period after rTMS, ranging from inhibition, in the case of low frequencies (\~1 Hz), or facilitation if high frequencies (equal to or greater than 5 Hz) are used.

Neuronavigation is a non-invasive method that allows the creation of computerized three-dimensional models of brain structures based on neuroimaging exams of each individual (e.g., cranial magnetic resonance imaging). As such, this method has been used for various purposes, such as assisting in neurosurgery or mapping functional regions of the brain, but also in the context of TMS (Transcranial Magnetic Stimulation). In this latter area, its use as support for TMS has been employed for therapeutic, diagnostic, and research purposes. The neuronavigation system consists of several components, namely a locating camera, locators for the TMS coil, an adjustable headband with locators, a calibration system for these elements, and the neuronavigation software, which is installed on a supporting computer.

Magnetic Resonance Imaging (MRI) is a non-invasive medical imaging technique that generates detailed images of the internal structures of the body using a strong magnetic field and radio waves. It provides high-resolution images of soft tissues, such as organs, muscles, and the brain, helping doctors diagnose and monitor various conditions, including injuries, tumors, and neurological disorders. MRI is particularly useful because it does not involve ionizing radiation, making it safer for patients than other imaging methods like X-rays or CT scans.