Invasive Brain–Computer Interfaces: 25 Years of Clinical Trials, Scientific and Practical Issues

A brain-computer interface (BCI) is a system that measures brain activity and converts it in real-time into functionally useful outputs to replace, restore, enhance, supplement, and/or improve the natural outputs of the brain. In invasive BCIs, electrodes are placed intracranially for more accurate and faster data exchange between the brain and external devices. The primary medical objective of these technologies is to compensate for motor or speech function in patients with tetraparesis and anarthria. In recent years, the emergence of new neuroimplants for BCIs and the results demonstrated in clinical trials have led to a notable increase in interest in these systems from the scientific community, investors, and the public. This review compares different types of medical invasive BCIs, analyzes and discusses the achievements and unsolved problems of clinical application of these neurotechnologies, as well as possible consequences and risks of their wider use.