Researchers stimulate deep brain tissue with heat and magnets

MIT researchers have devised a way to stimulate tissue deep in the brain without having to implant permanent electrodes. This benefit may provide a better understanding of intact brain regions and aid in the treatment of neurological disorders.

Currently, doctors perform brain stimulation treatments with electrical pulses in people with Parkinson’s. These treatments work, but are very invasive because electrodes are implanted directly into the brain.

For a study, the results of which have been published in Science, researchers injected magnetic iron oxide particles of 22 nanometers in diameter into the brains of mice. When the mouse was then exposed to an alternating magnetic field, the nanoparticles heated up. This resulted in an increase in temperature to which the temperature-sensitive ion channels TRPV1, also called capsaicin receptors, reacted.

The neurons in the brain are normally not sensitive to temperature. In order to make the neurons heat-sensitive, the researchers use a method in which a virus deposits other genes in cells in order to introduce a specific property in this way. The nanoparticles have virtually no interaction with surrounding tissue when heated and generally remain where they are inserted, enabling long-term treatments.

The technique is partly borrowed from cancer research, which uses magnetic fields to destroy cancer cells by heating them. In this case, the neurons are only excited, without destroying them. The magnetic particles have been used as a contrast medium for decades and are considered relatively safe. The nanoparticles remain in the mouse brain for just over a month.