Neuromagnetic Characterization of the Human Secondary Somatosensory Cortex

This thesis aims to characterize functions of the secondary somatosensory cortex SII in humans by means of neuromagnetic recordings. It starts with a review of literature about methodological considerations concerning the generation of neuromagnetic fields and how they can be measured and modeled. Then follows a brief overview of the somatosensory system, its receptors, ascending pathways, and cortical regions. The main part of the text summarizes the individual publications. Studies I and II show a strong interaction at SII between inputs of the two hands and of different fingers in the same hand, suggesting that SII plays an important role in integrating sensory information from the two body halves. Studies III and IV reveal left hemisphere-dominant SII activation for median nerve stimulation and passive movements of the index finger, suggesting hemispheric specialization for the processing of somatosensory information. Study V analyzes functional connectivity between SI and SII cortices by means of phase-locked activity. Study VI shows that SII activation is distinctly affected by contraction of different muscles. Altogether these studies provide an insight in to the role of SII in somatosensory processing.