Neuromagnetic characterization of the human secondary somatosensory cortex
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Doctoral thesis (article-based)
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AbstractThis 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.
magnetoencephalography, human, cortex, somatosensory, SI, SII, passive movement, phase-locked activity, hemispheric dominance, muscle contraction
- Simões C, and Hari R. Relationship between responses to contra- and ipsilateral stimuli in the human somatosensory cortex SII. NeuroImage 1999, 10: 408-416.
- Simões C, Mertens M, Forss N, Jousmäki V, Lütkenhöner B, and Hari R. Functional overlap of finger representations in the human SI and SII cortices. J Neurophysiol 2001, 86: 1661-1665.
- Simões C, Alary F, Forss N, and Hari R. Left-hemisphere dominant activation after bilateral median nerve stimulation. NeuroImage 2002, 15: 686-690.
- Alary F, Simões C, Jousmäki V, Forss N, and Hari R. Cortical activation associated with passive movements of the human index finger: an MEG study. NeuroImage 2002, 15: 691-696.
- Simões C, Jensen O, Parkkonen L, and Hari R. Phase-locking between human SI and SII cortices. Report TKK-KYL-007, November 2002:1-16.
- Lin Y, Simões C, Forss N, and Hari R. Differential effects of muscle contraction from various body parts on neuromagnetic somatosensory responses. NeuroImage 2000, 11: 334-340.