Transcranial magnetic stimulation can enhance perception and cognition
In transcranial magnetic stimulation, strong magnetic fields generated by specific coils placed on top of the scalp induce currents in the underlying tissue that extend to cortical tissue. Whilst transcranial magnetic stimulation has been traditionally considered as a method that disrupts the functioning of the targeted cortical locations, thus allowing causal testing of the roles of cortical areas in perceptual and cognitive functions by measuring performance decrements in specific behavioral tasks, there are also reports of performance enhancements following transcranial magnetic stimulation. Such findings have been generally considered to be surprising, but given that observations of performance enhancement have kept accumulating, they cannot be written off as erroneous chance findings.
In their recent review article, Drs. Bruce Luber and Sarah Lisanby (2013) systematically go over the findings on performance enhancement observed in transcranial magnetic stimulation studies. They nicely divide the reported effects into three classes, 1) some non-specific effects caused possibly by increased arousal due to the loud clicks and muscle stimulation, 2) some specific performance enhancement effects caused by taking out of areas that would normally compete with and interfere processing in the areas that are important for the task at hand, and 3) “genuine” performance enhancement effects. The authors also nicely discuss critical factors that give rise to performance enhancement such as strength, and specific rates, of stimulation.
Overall, this review article provides a very nice introduction to these less-well known but highly interesting effects of transcranial magnetic stimulation. The observations that transcranial magnetic stimulation can enhance perception and cognition are indeed highly promising also from the perspective of clinical research and ultimately development of novel clinical treatment and rehabilitation methods. Given that transcranial magnetic stimulation is a relatively non-specific method that stimulates rather extensive cortical areas, advances in stimulation technology, especially in case of patients where non-invasive methods are not the only option, will undoubtedly provide fascinating additional possibilities in the future that results obtained with transcranial magnetic stimulation pave way for in a very important way.
Reference: Luber, Bruce, Lisanby, Sarah H., Enhancement of human cognitive performance using transcranial magnetic stimulation (TMS). NeuroImage (2013), e-publication ahead of print. http://dx.doi.org/10.1016/j.neuroimage.2013.06.007