Neuromagnetic activation of primary and secondary somatosensory cortex following tactile-on and tactile-off stimulation.
OBJECTIVE
Magnetoencephalography (MEG) recordings were performed to investigate the cortical activation following tactile-on and tactile-off stimulation.


METHODS
We used a 306-ch whole-head MEG system and a tactile stimulator driven by a piezoelectric actuator. Tactile stimuli were applied to the tip of right index finger. The interstimulus interval was set at 2000 ms, which included a constant stimulus of 1000 ms duration.


RESULTS
Prominent somatosensory evoked magnetic fields were recorded from the contralateral hemisphere at 57.5 ms and 133.0 ms after the onset of tactile-on stimulation and at 58.2 ms and 138.5 ms after the onset of tactile-off stimulation. All corresponding equivalent current dipoles (ECDs) were located in the primary somatosensory cortex (SI). Moreover, long-latency responses (168.7 ms after tactile-on stimulation, 169.8 ms after tactile-off stimulation) were detected from the ipsilateral hemisphere. The ECDs of these signals were identified in the secondary somatosensory cortex (SII).


CONCLUSIONS
The somatosensory evoked magnetic fields waveforms elicited by the two tactile stimuli (tactile-on and tactile-off stimuli) with a mechanical stimulator were strikingly similar. These mechanical stimuli elicited both contralateral SI and ipsilateral SII activities.


CONCLUSIONS
Tactile stimulation with a mechanical stimulator provides new possibilities for experimental designs in studies of the human mechanoreceptor system.
Onishi
Hideaki
H
Niigata University of Health and Welfare, Department of Physical Therapy, 1398 Shimami-cho, Kita-ku, 950-3198 Niigata, Japan. onishi@nuhw.ac.jp
Oyama
Mineo
M
Soma
Toshio
T
Kubo
Masayoshi
M
Kirimoto
Hikari
H
Murakami
Hiroatsu
H
Kameyama
Shigeki
S
D000328:Adult; D001931:Brain Mapping; D005385:Fingers / Q000294:innervation; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D010812:Physical Stimulation / Q000379:methods; D011601:Psychophysics; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects; D013003:Somatosensory Cortex / Q000033:anatomy & histology / Q000502:physiology*; D013997:Time Factors; D014110:Touch / Q000502:physiology*; D055815:Young Adult