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Biomag 96 pp 1130-1133 | Cite as

EEG and MEG Source Analysis of Somatosensory Evoked Responses to Mechanical Stimulation of the Fingers

  • D. Cheyne
  • L. E. Roberts
  • W. Gaetz
  • D. Bosnyak
  • H. Weinberg
  • B. Johnson
  • C. Nahmias
  • L. Deecke

Abstract

Previous MEG and EEG studies have successfully utilized electrical stimulation of the digits in order to study generators of early responses in the human primary somatosensory cortex [1–3]. Natural stimulation of the somatosensory system using vibratory pulses to the tips of the digits has been found to elicit qualitatively different responses in the EEG [4, 5] presumably due to the activation of different neuronal pathways. Similar responses have been observed in the MEG to transient mechanical stimuli producing large responses at latencies of 50 msec, corresponding to the electrical P50 response [6, 7]. A more recent study [8] also noted MEG responses at 70 msec latencies in some subjects resembling the N70 component described by Hämäläinen and co-workers [4]. The earlier, P50 response is presumed to reflect activation of primary sensory cortex (SI). A study of mechanically evoked epidural and single unit responses in waking monkeys [5] found that this component was associated with a period of inhibitory input to neurons in areas 3b and 1, whereas the later, slow component (N70) was not associated with activity in SI and appeared to arise from other cortical areas, such as SII. The magnetically recorded P50 (P50m) appears to be the largest and most consistent MEG event recorded during transient tactile stimulation in humans and its potential application for somatotopic mapping studies [6, 7] warrants further investigation of its neural generation. Moreover, the marked orthogonality of the EEG and MEG topographies of the P50 response makes it an ideal candidate for the comparison and/or combination of EEG and MEG localization methods. The current study compared separate high-density, 32 channel EEG and 143 channel MEG recordings in two subjects using identical stimulation paradigms in order to compare dipole source locations in somatosensory cortex obtained separately for each method. In addition, 3-dimensional MRI was obtained for both subjects in order to constrain source model information as well as aid in the integration of coordinate systems for the MEG and EEG source models.

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References

  1. [1]
    Hari, R. and Kaukoranta E. Neuromagnetic studies of somatosensory system: principles and examples. Prog. Neurobiol., 1985, 24: 233–256.CrossRefGoogle Scholar
  2. [2]
    Buchner, H., Adams, L., Müller, A., Ludwig, I., Knepper, A., Thron, A., Niemann, K. and Scherg, M. Somatotopy of human hand somatosensory cortex revealed by dipole source analysis of early somatosensory evoked potentials and 3D-NMR tomography. Electroenceph. clin. Neurophysiol., 1995, 96: 121–134.CrossRefGoogle Scholar
  3. [3]
    Buchner, H., Fuchs, M., Wischmann, H-A., Dössel, O., Ludwig, I., Knepper, A. and Berg., P. Source analysis of median nerve and finger stimulated somatosensory evoked potentials: Multichannel simultaneous recording of electric and magnetic fields combined with 3D-MR tomography. Brain Topog., 1994: 299–310Google Scholar
  4. [4]
    Hämäläinen, H. Kekoni, J., Sams, M., Reinikainen, K. and Näätänen R. Human somatosensory evoked potentials to mechanical pulses and vibration: contributions of SI and SII somatosensory cortices to P50 and P100 components. Electroenceph. clin. Neurophysiol., 1990, 75:13–21.CrossRefGoogle Scholar
  5. [5]
    Gardner, E.P., Hämäläinen, H.A., Warren, S., Davis, J. and Young W. Somatosensory evoked potentials (SEPs) and cortical single unit responses elicited by mechanical tactile stimuli in awake monkeys. Electroenceph. clin. Neurophysiol., 1984, 58: 537–552.CrossRefGoogle Scholar
  6. [6]
    Suk, J., Ribary U., Cappell, J., Yamamoto T. and Llinás R. Anatomical localization revealed by MEG recordings of the human somatosensory system. Electroenceph. clin. Neurophysiol., 1991, 78:185–196.CrossRefGoogle Scholar
  7. [7]
    Yang, T.T., Gallen C.C., Schwartz, B.J., and Bloom, F.E. Noninvasive somatosensory homunculus mapping in humans by using a large-array biomagnetometer. Proc. Natl. Acad. Sci., 1993, 90: 3098–3102.ADSCrossRefGoogle Scholar
  8. [8]
    Cheyne, D., Weinberg H., Hattori, H., Gordon, R., Vrba, J. and Burbank M. In: N. Tepley and G. L. Barkley (Eds.) Characterisation of human sensorimotor cortex using whole-cortex MEG: implications for clinical use. Proceedings of the North American Biomagnetism Action Group Annual Meeting. Detroit, 1994.Google Scholar
  9. [9]
    Vrba J., Angus, V., Betts K., Burbank M., Cheung T., Fife A., Haid G., Kubik P., Lee S., McCubbin J., McKay J., McKenzie, Robinson, S., D., Spear P., Taylor B., Tillotson M., Cheyne D. and Weinberg H. A 143 channel, whole cortex MEG system (these proceedings).Google Scholar
  10. [10]
    Stok C. J. The inverse problem in EEG and MEG with application to visual evoked responses. Ph.D. Thesis, 1986, Krips Repro Meppel.Google Scholar

Copyright information

© Springer Science+Business Media New York 2000

Authors and Affiliations

  • D. Cheyne
    • 1
  • L. E. Roberts
    • 2
  • W. Gaetz
    • 2
  • D. Bosnyak
    • 2
  • H. Weinberg
    • 1
  • B. Johnson
    • 1
  • C. Nahmias
    • 3
  • L. Deecke
    • 4
  1. 1.Brain Behaviour LaboratorySimon Fraser UniversityBurnabyCanada
  2. 2.Department of PsychologyMcMaster UniversityHamiltonCanada
  3. 3.Department of Nuclear MedicineMcMaster UniversityHamiltonCanada
  4. 4.Neurological ClinicUniversity of ViennaViennaAustria

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