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Human second somatosensory area: subdural and magnetoencephalographic recording of somatosensory evoked responses
  1. Tatsuya Mimaa,
  2. Akio Ikedaa,
  3. Takashi Nagaminea,
  4. Shogo Yazawaa,
  5. Takeharu Kuniedab,
  6. Nobuhiro Mikunib,
  7. Waro Takib,
  8. Jun Kimurac,
  9. Hiroshi Shibasakia
  1. aDepartment of Brain Pathophysiology, bDepartment of Neurosurgery, cDepartment of Neurology, Kyoto University School of Medicine, Shogoin, Sakyo-ku, Kyoto 606-01 Japan
  1. Dr Hiroshi Shibasaki, Department of Brain Pathophysiology, Kyoto University School of Medicine, Shogoin, Sakyo-ku, Kyoto 606-01, Japan.


OBJECTIVE To investigate somesthetic functions of the perisylvian cortex. Methods—Somatosensory evoked magnetic fields (SEFs) and somatosensory evoked potentials (SEPs) of the perisylvian cortex were recorded directly from subdural electrodes in a patient with a left frontal brain tumour.

RESULTS The most prominent SEP components after electrical stimulation of the right and left hands and the right foot were double peaked negativity recorded just above the sylvian fissure (latency 80 to 150 ms), respectively (N1a and N1b). Generator sources for the magnetoencephalographic counterparts of those peaks (N1a(m) and N1b(m)) were both localised at the upper bank of the sylvian fissure, and those of N1a(m) were more anteromedially located than those of N1b(m).

CONCLUSIONS These findings suggest the existence of at least two separate somatosensory areas within the human perisylvian cortex.

  • somatosensory evoked potentials
  • subdural recording
  • magnetoencephalography
  • human second somatosensory area

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