With the advent of noninvasive brain stimulation techniques, clinicians now have at their disposal easy, safe methods to modulate brain activity. Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (TDCS) use magnetic fields or electrical currents delivered from outside the brain to change neuronal excitation in the brain.
But what are the best targets? What are the most promising indications? Where does neuromodulation give the biggest bang for the buck? Joan A. Camprodon, MD, PhD, director of the Division of Neuropsychiatry at Mass General and founding director of the Mass General Transcranial Magnetic Stimulation service, wants to figure that out. By integrating clinical and research efforts, Camprodon and his group are working to uncover the brain circuits that are altered in neuropsychiatric disease, and the best ways to deploy noninvasive neurostimulation to right them.
For starters, Camprodon says that the effective use of neuromodulation requires clinicians to transcend traditional clinical diagnostic boundaries when evaluating patients. Rather than treat by disease, the neuropsychiatry division focuses on clinical dimensions—the aspects of mood, behavior or cognitive function that are altered in neuropsychiatric disease.
“Instead of just saying that a patient has depression, or schizophrenia, or stroke, or epilepsy, we focus on transdiagnostic problems such as maladaptive reward processing or amotivation, ineffective inhibitory control or impulsivity, dysexecutive effects such as poor planning or multitasking, et cetera,” he explains. Those clinical domains more closely correspond to brain circuits that may be amenable to neuromodulation.
Next, Camprodon’s group is letting an old, but effective treatment inform their new efforts. The first form of brain stimulation used in clinical practice, electroconvulsive therapy (ECT), still offers a viable approach to treatment-resistant major depressive disorder, mania, psychosis and catatonia, among others.
ECT is quite effective—for some forms of depression, response rates range from 70 to 90 percent. While safe, the procedure does require general anesthesia, and comes with the potential for side effects that include transient memory loss.
Dr. Camprodon’s laboratory and clinical service at MGH work towards defining individualized targets for brain stimulation therapies by defining the specific maladaptive brain circuit dynamics of each patient.