Neural mechanisms for generation of tactile interference effects on somatosensory evoked magnetic fields in humans.
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.
Tanosaki
Masato
M
Department of Integrated Neuroscience, Tokyo Institute of Psychiatry, 2-1-8 Kamikitazawa, Setagaya-Ku 156-8585, Japan. tanosaki@prit.go.jp
Suzuki
Atsushi
A
Takino
Ryosuke
R
Kimura
Tomoaki
T
Iguchi
Yoshinobu
Y
Kurobe
Yuji
Y
Haruta
Yasuhiro
Y
Hoshi
Yoko
Y
Hashimoto
Isao
I
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*