Characterization of the Somatosensory System

For the characterization of the somatosensory system in the mammalian brain, somatosensory evoked potentials (SEP) and fields (SEF), SEP/SEF source analysis and targeted transcranial electric (TES) and magnetic (TMS) brain stimulation have become important techniques over the last decades. They were also shown to contribute to an improved diagnosis and therapy of neurological diseases such as multiple sclerosis (MS) and epilepsy. In this chapter, we will review the most recent advances of these modern methods and point out their translational potential for clinical use. We will start by describing the generation process of evoked responses with a focus on not only the high temporal resolution information contained in these data, but especially also the rich spatial information when using (combined) multichannel electroencephalography (EEG) and magnetoencephalography (MEG). This topographical information and the use of individualized realistic head models extracted from magnetic resonance imaging (MRI) data enables the reconstruction of the underlying sources in the brain using source analysis techniques. We will then discuss state-of-the-art individually optimized multichannel TES and TMS brain stimulation methods for a targeted manipulation of reconstructed sources in the brain. Finally, we will indicate how these modern noninvasive methods can be used to characterize the somatosensory system on an individual level and how they can be applied to gain a deeper understanding of the neural networks in MS and epilepsy.