Clinical Electrophysiology of the Somatosensory Cortex

The clinical electrophysiology of the human somatosensory cortex was investigated with a combined approach using cortical stimulations and somatosensory evoked responses on electrocorticography, scalp-EEG, and magnetoencephalography, a new neurophysiological technique. The spatiotemporal structure of the evoked response was studied with novel biophysical modeling techniques which allowed identification of the three-dimensional intracerebral location, time activity, and interaction of the neuronal sources in human somatosensory cortex. Thus, new aspects on the functional anatomy of the human somatosensory cortex could be elicited. Furthermore, the somatotopy of the hand somatosensory cortex was investigated. Clinically, the results of comparison of the different techniques can improve the non-invasive localization criteria for primary motor and somatosensory cortex which is important in patients undergoing neurosurgical procedure adjacent to central fissure. §Die funktionelle Organisation und Somatotopik des menschlichen somatosensorischen Kortex wurde mittels kortikaler Stimulationen und mittels somatosensorisch evozierter Potentiale in der Elektrokortikographie, im Oberflächen-EEG und in der Magnetoencephalographie - einer neuen neurophysiologischen Methode - untersucht. Neue Aspekte betreffend die Physiologie und die nicht-invasive Lokalisation des somatosensorischen Kortex werden diskutiert. The functional anatomy of human somatosensory cortex is of both scientific and clinical interest. Scientifically, it provides insights in information processing in the human brain. Clinically, it helps to avoid neurological deficits by sparing essential brain regions during neurosurgical procedures adjacent to central fissure. In the present study the functional organization of the human somatosensory cortex was investigated with electrophysiological techniques using a combined approach of cortical stimulations and somatosensory evoked responses on electrocorticography, scalp-EEG, and magnetoencephalography. The spatiotemporal structure of the evoked response was studiedwith biophysical modeling techniqueswhich allowed identification of the three-dimensional intracerebral location, time activity, and interaction of the neuronal sources activated following peripheral somatosensory stimulation. Furthermore, the somatotopic organization ofhand and lip somatosensory cortex was investigated. The relative value of invasive (cortical stimulations and electrocorticography) and non-invasive (scalp-EEGand magnetoencephalography) was assessed. The combined use ofscalp-EEG and magnetoencephalography was useful to increase non-invasive localization accuracy. I want to thank several people who significantly contributed in completion of the present work. Univ. -Prof Dr. Luder Deecke, Chairman of the Neurological University Clinic, Vienna, Austria, supported me throughout my career at the Neurological University Clinic in Vienna since 1985. Dr. William W Sutherling, Associate Professor at the University of California, Los Angeles, who was my advisor during my stay from 1987-1989 at the Department ofNeurology, University of California, Los Angeles where most of the present work was done.