Somatotopy of human hand somatosensory cortex as studied in scalp EEG

• Published in: Electroencephalography and clinical neurophysiology Vol. 88; no. 4; pp. 271 - 279
• Main Authors: Baumgartner, Christoph, Doppelbauer, Andreas, Sutherling, William W., Lindinger, Gerald, Levesque, Michel F., Aull, Susanne, Zeitlhofer, Josef, Deecke, Lüder
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 01.07.1993; Amsterdam Elsevier
• Subjects: Adult; Biological and medical sciences; Brain Mapping; Dipole modelling; Electric Stimulation; Electroencephalogram; Electroencephalography; Epilepsy - physiopathology; Evoked Potentials, Somatosensory - physiology; Female; Functional anatomy; Fundamental and applied biological sciences. Psychology; Hand - innervation; Humans; Reaction Time - physiology; Reference Values; Scalp - physiology; Somatosensory cortex; Somatosensory Cortex - physiology; Somatosensory Cortex - physiopathology; Somatosensory evoked potentials; Somatotopic organization; Somesthesis and somesthetic pathways (proprioception, exteroception, nociception); interoception; electrolocation. Sensory receptors; Vertebrates: nervous system and sense organs; Somatosensory cortex; Functional anatomy; Somatosensory evoked potentials; Electroencephalogram; Somatotopic organization; Dipole modelling; Human; Somatotopy; Somesthetic pathway; Topography; Central nervous system; Electrophysiology; Dipole; Electroencephalography; Somatosensory evoked potential; Hand; Brain (vertebrata)
• ISSN: 0168-5597; 0013-4694; 1872-6380
• DOI: 10.1016/0168-5597(93)90051-P

We recorded somatosensory evoked potentials (SEPs) in scalp EEGs during stimulation of the median nerve, the ulnar nerve and the individual digits in 3 normal subjects and in 1 epilepsy patients. In this patient we also measured SEPs from chronically indwelling subdural grid electrodes during electrocorticography (ECoG). We applied dipole modelling techniques to study the 3-dimensional intracerebral locations and time activities of the neuronal sources underlying stimulation of different peripheral receptive fields. The sources underlying median nerve SEPs were located an average of 10.8 mm lateral inferior to those underlying ulnar nerve SEPs. Digit SEP sources showed a somatotopic arrangement from lateral inferior to medial superior in the order thumb, index finger, middle finger, ring finger and little finger, with some overlap or reversal for adjacent digits. The average distance between thumb and little finger was 12.5 mm. Thumb, index finger and middle finger were clustered around median nerve cortical representation, whereas ring finger and little finger were arranged around ulnar nerve cortex. In the epilepsy patient, the source localizations obtained in scalp EEGs showed good agreement with those on ECoGs. We conclude that SEPs recorded in scalp EEGs can be used to study functional topography of human somatosensory cortex non-invasively.