title: Neural mechanisms for generation of tactile interference effects on somatosensory evoked magnetic fields in humans.
abstract: OBJECTIVE
  We examined modification of somatosensory evoked fields following electric middle finger stimulation with interference to the same and surrounding digits in 13 subjects.
  
  
  METHODS
  During electric middle finger stimulation, concurrent tactile stimulation was applied to the middle finger, to the index and ring fingers, and to the thumb and the little finger, individually.
  
  
  RESULTS
  The amplitudes of the N20m and the P30m were significantly reduced by the interference to the middle finger, and to the index and ring fingers. The former interference induced more prominent attenuation than the latter. The amplitudes of the P60m did not show significant changes by any kind of the interference.
  
  
  CONCLUSIONS
  The N20m and the P30m were attenuated according to the cortical distance between electrically and mechanically activated 3b areas. Pyramidal neurons are interconnected by intrinsic horizontal collaterals, even if their representations are segregated. The activation of the intrinsic collaterals induces direct excitation and indirect inhibition (via inhibitory interneurons) to the target pyramidal neurons. The result indicates that the activation of the intrinsic collaterals inhibits, on balance, the postsynaptic pyramidal targets, thereby generating the attenuation of the N20m and P30m.
authors.affiliation: Department of Integrated Neuroscience, Tokyo Institute of Psychiatry, 2-1-8 Kamikitazawa, Setagaya-Ku 156-8585, Japan. tanosaki@prit.go.jp
authors.forename: Masato
authors.initials: M
authors.lastname: Tanosaki
authors.forename: Atsushi
authors.initials: A
authors.lastname: Suzuki
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Takino
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Kimura
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Iguchi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kurobe
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Haruta
authors.forename: Yoko
authors.initials: Y
authors.lastname: Hoshi
authors.forename: Isao
authors.initials: I
authors.lastname: Hashimoto
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D005385:Fingers / Q000294:innervation / Q000502:physiology; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D009434:Neural Pathways; D017966:Pyramidal Cells / Q000502:physiology; D013003:Somatosensory Cortex / Q000166:cytology / Q000502:physiology*; D014110:Touch / Q000502:physiology*