Non-invasive brain stimulation (NIBS) refers to a series of methods used to safely modulate human brain function by transiently altering the excitability state of targeted neurons. There has been a surge of interest in NIBS methods over the past 30 years. Research scientists use NIBS to test causal hypotheses about brain-behavior relationships; clinicians have recognized the potential of NIBS as providing a new intervention in the treatment of neurological and psychiatric disorders.
Despite this potential, there are substantial concerns about the reliability and robustness of the physiological and behavioral changes resulting from current NIBS methods. The two most common NIBS methods are transcranial electrical stimulation (tES) and transcranial magnetic stimulation (TMS). With tES, a continuous modulatory signal can be induced, allowing the experimenter to increase or decrease the state of excitability of the targeted neural region. Moreover, the frequency of this signal can be varied, enhancing or attenuating endogenous brain rhythms. However, due to safety concerns with direct electrical stimulation, tES can only induce very weak changes in neural excitability, with an upper bound less than 1 V/m on the cortical surface. In addition, the induced changes lack spatial specificity. In contrast, magnetic stimulation can safely induce much stronger changes with excellent spatial specificity. However, conventional TMS lacks frequency specificity.
To address these concerns, we have developed a new NIBS system. We believe our new method can produce much more reliable, and thus, effective, effects on brain function.