It is clear that for noninvasive neuromodulation to advance, a concerted effort must understand how these interventions impact neural circuit functions.
FREMONT, CA: Though developed by scientists and clinicians to know and modulate brain function, brain stimulation devices are now being sold to consumers directly to promise they will improve brain function or wellbeing. These products claim they can boost cognitive performance, mathematical ability, attention span, problem-solving, memory, coordination, and even treat depression and chronic pain. It was clear that much work remains to be done to understand the short- and long-term impact of using these devices for medical and non-medical applications.
The development of stimulators that can deliver long trains of closely spaced pulses allows repetitive transcranial magnetic stimulation (rTMS)—this increased TMS scope from a neurophysiological probe to a device with the ability to alter brain function. The increasing scientific and clinical interest in noninvasive brain stimulation created by TMS also led to the revitalization of transcranial direct current stimulation (tDCS), a technique applied to humans and animal models. Unlike TMS, which can create a direct neurostimulation impact, tDCS does not usually elicit action abilities. Instead, tDCS is thought to show a modulatory impact on brain function: the externally applied electric field displaces ions within neurons, changing neuronal excitability and modulating individual neurons' firing rate. Most of the direct-to-consumer brain stimulation products are tDCS devices.
Noninvasive brain stimulation is of significant interest to clinicians and researchers, given its ability to study brain physiology and treat the brain's diseases. It provides advantages as a diagnostic device in that it can be used to observe disease-related alterations in brain activation, inhibition, or connectivity. TMS devices for therapeutic can be used with patients suffering from treatment-resistant depressions. Based on a controlled clinical trial, the FDA permitted premarket approval of a TMS device for the treatment of pain associated with a headache with aura.
Researchers are also studying rTMS to treat a range of other neurological diseases and disorders, including stroke rehabilitation, tinnitus, chronic pain, obsessive-compulsive disorder, epilepsy, post-traumatic stress disorder, and movement disorders such as Parkinson’Parkinson'sIn general, researchers have found that for any indication, patients require repeated rTMS treatment sessions, and combining rTMS with pharmacological or behavioral therapy may enhance treatment effects. These observations are not surprising, given that neuroplasticity is fundamental to the therapeutic mechanism of noninvasive brain stimulation.