Published On May 13, 2015
A Shock From Outside
Implanted devices are just one approach to neuromodulation therapy. Transcranial stimulation is achieving results and reaching new audiences.
Not every electrical therapy for the nervous system involves surgery. In transcranial direct current stimulation, or tDCS, a dose of low-intensity electrical current—about 1/400 of that used in electroshock treatment—is administered to the brain for 20 to 30 minutes, via two electrodes placed on a patient’s temples.
The treatment is already being used to help relieve major depression. In a study of 120 patients with moderate to severe depression, published in JAMA Psychiatry in 2013, researchers found that tDCS worked about as well as a low dose of the antidepressant sertraline (Zoloft). A combination of the antidepressant and electrical stimulation worked better than either therapy on its own.
Because tDCS devices are relatively inexpensive and easy to use (often requiring just a 9-volt battery for power), patients can treat themselves at home. Fisher Wallace Laboratories markets a tDCS device that is FDA-cleared for treatment of depression and anxiety that retails for about $700. In fact, the ready availability of such devices has spawned inventive applications. One neuromodulation headset from foc.us is marketed to hard-core videogamers with a promise to “unleash your inner gamer.” The foc.us headset sends waves of alternating electrical current to the prefrontal cortex, and the stated benefits—increased “working memory and focus”—are based on Air Force research that found mild electrostimulation improved learning and enhanced performance in a difficult situation.
While tDCS appears safe, it is far from precise and only penetrates to shallow regions, because the skull blocks most of the current. Another method, called transcranial magnetic stimulation (TMS), uses magnetic fields to induce current deeper into the brain, typically about two inches. (Unlike the mild electric current from tDCS, magnetic pulses pass easily through the skull and brain tissue.)
Nanotechnology could soon make it possible to target specific parts of the deep brain without surgery or wires. Polina Anikeeva, an assistant professor in materials science and engineering at MIT, recently published results of a study using magnetic “rust” nanoparticles to influence brain activity in mice. At 20 nanometers in diameter, approximately 1/4,000 the diameter of a human hair, these magnetic particles can be injected into specific areas of the brain and “turned on” with an external alternating magnetic field. Such an approach could translate to a new kind of prescription for people with depression or other neurologic disorders: a targeted nanoparticle injection and nightly “recharging” of their brains by means of a bed or pillow equipped with a magnetic coil.