MIT researchers have developed a method to stimulate brain tissue using external magnetic fields and injected magnetic nanoparticles - a technique allowing direct stimulation of neurons, which could be an effective treatment for a variety of neurological diseases, without the need for implants or external connections. Previous efforts to stimulate the brain using pulses of electricity have proven effective in reducing or eliminating tremors associated with Parkinson’s disease, but the treatment has remained a last resort because it requires highly invasive implanted wires that connect to a power source outside the brain. For their method, the MIT team injected magnetic iron oxide particles only 22 nanometers in diameter into the brain. When exposed to an external alternating magnetic field, which can penetrate deep inside biological tissues, these particles rapidly heat up. This video shows a calcium ion influx into neurons as a result of magnetothermal excitation with alternating magnetic fields in the presence of magnetic nanoparticles. Neurons on the right have been heat-sensitized with the capsaicin receptor TRPV1, neurons on the left have not.