IS 15. Flashes of insight: Non-conventional NIBS reveals novel ways to stimulate the brain

Abstract

Modulating, disrupting or otherwise interfering with the activity of the cerebral cortex by non-invasive, external stimulation methods not only offers the possibility of clinical intervention in neurological and psychiatric diseases, but provides us with a powerful research tool for understanding the workings of the intact human brain. In the past years new non-conventional, non-invasive brain stimulation (NIBS) techniques have been developed. Application of near-infrared light to the scalp has recently been introduced in order to treat neurological conditions such as stroke and the treatment of traumatic brain disorders ( Hashmi et al., 2010 ). Another very simple method, the application of static magnetic fields (tSMS) through the scalp by using small cylindrical magnets, has been shown to induce robust effects on levels of cortical excitability in healthy subjects ( Oliviero et al., 2011 ). Nevertheless, a deeper knowledge of the mechanisms of how these methods work on a neuronal level, is required. In our laboratory we have demonstrated that applying near-infrared light at a wavelength of 810 nm for 10 min to the primary motor cortex (M1), results in cortical excitability changes, assessed by means of motor-evoked potentials (MEP). MEP amplitudes showed a 20–40% decrease compared to sham stimulation, for up to 1 h post-stimulation. Furthermore, it was observed that the stimulation modified the long intracortical inhibition. Similarly, with the application of tSMS to the M1, an inhibition could be observed. On the functional level it has been demonstrated that both of these methods can modify implicit motor learning. These non-conventional NIBS techniques may thus be opening new research domains for influencing brain activity and to treat neurological and psychiatric disorders in a non-invasive way.