In the past 50 years, an ethical-legal boundary has been drawn between treatment and research. It is based on the reasoning that the two activities pursue different purposes. Treatment is aimed at achieving optimal therapeutic benefits for the individual patient, whereas the goal of scientific research is to increase knowledge, in the public interest. From this viewpoint, the patient's experience should be clearly distinguished from that of a participant in a clinical trial. On this premise, two parallel and mutually exclusive regimes have been established. Yet in the case of deep brain stimulation (DBS), this presentation is a poor fit, for both the patient's lived experience and medical practice and research. The frictions may be explained by the specificities of the treatment (including surgery and medical devices) and of the pathologies concerned (chronic and evolutive), and by the characteristics of the medical team implementing the treatment. These particularities challenge the dominant frame of reference in medical bioethics and cause difficulties for the current legal framework in fulfilling its dual role: to protect patients while supporting the development of innovative treatments. The dominant model is still the clinical trial for medication safety and legal requirements of drug market regulation. However, DBS forces us to reflect on a medical device that is permanently implanted in the brain by highly specialized multi-disciplinary neurosurgical teams, for the treatment of chronic evolutive diseases. These devices demand fine-tuning on a case-by-case basis and there is still a lot to discover about why DBS is effective (or not). As a result, the wall between treatment and research is osmotic: many discoveries are made incidentally, in the course of treatment. The following study begins with these observations, and suggests that we review legal provisions (especially in French and United States law) so that they are better adapted to the first-person needs and experience of the patient undergoing brain stimulation.