Neuromagnetic studies of the lip area of primary somatosensory cortex in humans: evidence for an oscillotopic organization

A. Mogilner, M. Nomura, U. Ribary, R. Jagow, F. Lado, H. Rusinek, R. Llinás

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Magnetic trigeminal somatosensory responses from human subjects were recorded using a 14-channel magnetoencephalographic system. Sensory stimuli comprising a 15-ms vibration at frequencies of 50 Hz, 150 Hz and 250 Hz were given at randomized interstimulus intervals. Using a single dipole model, the neuronal sources of the evoked responses were determined, and mapped onto magnetic resonance images of each subject. Source localization analysis was based on the main peak of the averaged signal (M55). All of the sources were located deep in the anterior bank of the postcentral gyrus, corresponding to area 3b of somatosensory cortex SI. In all cases, the source for the upper lip was significantly higher in the vertical axis (0.6-1.1 cm) than for the lower lip, while the lower lip stimulation produced a larger response than the upper lip. Furthermore, statistically significant differences were found between the locations of the dipoles evoked by different frequency stimulation. The location of the response shifted with change in stimulation frequency, showing a trend among all subjects with a medial shift between 150 and 250 Hz for both upper and lower lip. The accuracy of source localization calculated from magnetic fields ranged between ±0.9 and ±3.0 mm (SEM). These results demonstrate (1) that a large area of the somatosensory cortex is utilized for lip representation and (2) that the spatial displacement of the trigeminal somatosensory response may be related to the discrimination of frequency.

Original languageEnglish (US)
Pages (from-to)137-147
Number of pages11
JournalExperimental Brain Research
Issue number1
StatePublished - May 1994
Externally publishedYes


  • Frequency discrimination
  • Human
  • Lip
  • Magnetoencephalography
  • Somatosensory cortex
  • Trigeminal nerve

ASJC Scopus subject areas

  • General Neuroscience


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