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PS-15-4 Somatosensory evoked magnetic fields following mechanical stimulation of the scalp in humans
Postersession 15. Magnetoencephalography(1): sornatosensoryevokedfields amplitude. When the lower lip was stimulated, the ECD of shortand middle- latency deflections were located at a site in the S1 inferior to or near those elicited in the upper lip stimulation. The ECD of P l l 0 m - N l l 0 m were located in the SII similar to that upon stimulation of the upper lip, but their directions were differentl
I PS-15-3 1 Topography of somatosensory evoked magnetic fields following posterior Ubial nerve stimulation Ryusuke Kakigi, Sachiko Koyama, Minoru Hoshiyama, Motoko Shimojo, Yoshihiro Kitamura, Shoko Watanabe.
Department of Integrative Physiology, National Institute for Physiological Sciences, Japan The topography of somatosensory evoked magnetic fields (SEFs) following stimulation of the right and left posterior tibial nerve was investigated in 5 normal subjects (10 nerves). The main deflections N37m-P45m-N60m-P75m and their counterparts P37m-N45mP60m-N75m were identified in the hemisphere contralateral to the stimulated nerve. Their equivalent current dipoles (ECDs) were located in the foot area of the primary sensory cortex (SI), probably in area 3b. Restricted minor deflections, P40m-N40m and N50m-P50m, were considered to be generated in area 1 in SI. As the generator sources of P37m-N37m, P40m-N40m and N45mP45m were temporally changed and interfered with each other, the direction of ECDs appeared to be rotated with the passage of time. Small middle-latency deflections, N100m-P100m, were clearly identified in 2 subjects. ECDs of these deflections were found in the second sensory cortex (SII), in both hemispheres, although they were clearer in the hemisphere contralateral to the stimulated nerve. In conclusion, short- and middle-latency SEFs are mainly generated in area 3b in SI contralateral to the stimulated nerve, and responses generated in area 1 of SI and SII affect the SEFs to some degree, but interindividual differences are large compared with SEFs evoked by upper limb stimulation.
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and thumb stimulation in any subjects. This finding may suggest that the receptive fields in the SII are not clearly separated.
I PS-15-5 1 Pain-related somatosensory evoked magnetic fields Yoshihiro Kitamura, Ryusuke Kakigi, Minoru Hoshiyama, Sachiko Koyama, Osamu Nagata, Yasuyuki Takeshima, Masahiro Mori, Motoko Shimojo, Shoko Watanabe. Department
of Integrative Physiology, National Institute for Physiological Sciences, Japan Somatosensory evoked magnetic fields (SEFs) following painful electrical stimulation of the finger were investigated in 5 normal subjects. Equivalent current dipoles (ECDs) of deflections shorter than 100 msec in latency were located in the primary sensory cortex (SI) in the hemisphere contralateral to the stimulated finger following either non-painful or painful stimulation. Two main deflections, N100m-P100m and P250m-N250m, were independently identified following painful stimulation, although they were not found in SEFs following non-painful weak stimulation. ECDs of the N100m-P100m were considered to be located in bilateral second sensory cortices (SII). ECDs of the P250m-N250m were identified in bilateral cingulate cortices and SII, but the intersubject difference was large. Therefore, we considered that contralateral SI and bilateral SII were initially activated by painful noxious stimulation, and then multiple areas including bilateral SII and cingulate cortices were activated. In E E G recordings (evoked potentials), no potential corresponding to N100m-Pl00m was found, probably because it was difficult to record activation in SII by EEG recordings. The P250 potential which corresponded to the P250m-N250m was clearly identified, probably because activation of multiple areas generated large long-duration E E G potentials which were maximal around the vertex unlike M E G recordings.
[1] Kakigi R et al: Electroenceph Clin Neurophysiol, in press.
I PS-15-61 Pain-related magnetic fields following painful CO2 laser stimulation in man
IPS-15-4 1 Somatosensory evoked magnetic fields
Ryusuke Kakiqi, Sachiko Koyama, Minoru Hoshiyama, Yoshihiro Kitamura, Motoko Shimojo, Shoko Watanabe.
following mechanical stimulation of the scalp in humans
Minoru Hoshiyama, Ryusuke Kakigi, Sachiko Koyama, Yoshihiro Kitamura, Motoko Shimojo, Shoko Watanabe.
Department of Integrative Physiology, National Institute for Physiological Sciences, Japan This is the first report on the brain responses following scalp stimulation in humans. Somatosensory evoked magnetic fields (SEFs) following mechanical stimulation by air-pressure-induced tapping applied to the forehead and occiput were examined in normal subjects. The equivalent current dipole (ECD) of the initial magnetic field, 1M, was identified in the primary somatosensory cortex (SI) in the hemisphere contralateral to the stimulation. It would be current source at the scalp area of Broadman's area 3b in SI, the posterior bank of the central sulcus, generated by the first branch of trigeminal nerve (forehead) or greater occipital nerve (occiput). No consistent ECD could be identified in the frontal, parietal, and occipital areas. The ECD position of 1M in SI following the scalp stimulation was close inferior to the hand area of the SI. The present results are consistent with the well-known somatotopic organization of S1. The ECD of the second magnetic field, 2M, was identified in bilateral second sensory cortices (SII) in the upper bank of the Sylvian fissure. There was no clear consistent difference between the ECD positions of 2M following scalp
Department of Integrative Physiology, National Institute for Physiological Sciences, Japan The initial somatosensory evoked magnetic fields following painful heat stimulation by CO2 laser beam (pain SEFs) applied to the upper and lower limb were investigated in normal subjects. The main deflections, "Pain M g ' and "Pain ME' following the arm and leg stimulation, respectively, were identified in the bilateral second sensory cortices (SII). Those responses could not be identified by recording the averaged electroencephalography (EEG). The onset latencies of Pain MA and Pain ML were approximately 150 and 200 msec, respectively. The equivalent current dipoles (ECDs) of pain SEFs were oriented primarily upper and anterior direction. No consistent ECD was found in the primary sensory cortex (SI) in each hemisphere. When the probe was centered around the Fz' (2 cm in front of Fz), Cz and Pz' (2 cm behind Pz) to investigate the detailed topography of the pain SEFs, no consistent ECD was identified. Though there is a possibility that ECDs generated in SI and other areas are radially-oriented which are not identified in the recording of magnetoencephalography (MEG), we consider that neurons in the bilateral SII are initially activated following painful heat stimulation, unlike tactile, vibratory or electrical stimulations, which generate ECDs in SI. [1] Kakigi R et al: Neuroscience Letters, in press.
I PS-15-3 1 Topography of somatosensory evoked magnetic fields following posterior Ubial nerve stimulation Ryusuke Kakigi, Sachiko Koyama, Minoru Hoshiyama, Motoko Shimojo, Yoshihiro Kitamura, Shoko Watanabe.
Department of Integrative Physiology, National Institute for Physiological Sciences, Japan The topography of somatosensory evoked magnetic fields (SEFs) following stimulation of the right and left posterior tibial nerve was investigated in 5 normal subjects (10 nerves). The main deflections N37m-P45m-N60m-P75m and their counterparts P37m-N45mP60m-N75m were identified in the hemisphere contralateral to the stimulated nerve. Their equivalent current dipoles (ECDs) were located in the foot area of the primary sensory cortex (SI), probably in area 3b. Restricted minor deflections, P40m-N40m and N50m-P50m, were considered to be generated in area 1 in SI. As the generator sources of P37m-N37m, P40m-N40m and N45mP45m were temporally changed and interfered with each other, the direction of ECDs appeared to be rotated with the passage of time. Small middle-latency deflections, N100m-P100m, were clearly identified in 2 subjects. ECDs of these deflections were found in the second sensory cortex (SII), in both hemispheres, although they were clearer in the hemisphere contralateral to the stimulated nerve. In conclusion, short- and middle-latency SEFs are mainly generated in area 3b in SI contralateral to the stimulated nerve, and responses generated in area 1 of SI and SII affect the SEFs to some degree, but interindividual differences are large compared with SEFs evoked by upper limb stimulation.
S121
and thumb stimulation in any subjects. This finding may suggest that the receptive fields in the SII are not clearly separated.
I PS-15-5 1 Pain-related somatosensory evoked magnetic fields Yoshihiro Kitamura, Ryusuke Kakigi, Minoru Hoshiyama, Sachiko Koyama, Osamu Nagata, Yasuyuki Takeshima, Masahiro Mori, Motoko Shimojo, Shoko Watanabe. Department
of Integrative Physiology, National Institute for Physiological Sciences, Japan Somatosensory evoked magnetic fields (SEFs) following painful electrical stimulation of the finger were investigated in 5 normal subjects. Equivalent current dipoles (ECDs) of deflections shorter than 100 msec in latency were located in the primary sensory cortex (SI) in the hemisphere contralateral to the stimulated finger following either non-painful or painful stimulation. Two main deflections, N100m-P100m and P250m-N250m, were independently identified following painful stimulation, although they were not found in SEFs following non-painful weak stimulation. ECDs of the N100m-P100m were considered to be located in bilateral second sensory cortices (SII). ECDs of the P250m-N250m were identified in bilateral cingulate cortices and SII, but the intersubject difference was large. Therefore, we considered that contralateral SI and bilateral SII were initially activated by painful noxious stimulation, and then multiple areas including bilateral SII and cingulate cortices were activated. In E E G recordings (evoked potentials), no potential corresponding to N100m-Pl00m was found, probably because it was difficult to record activation in SII by EEG recordings. The P250 potential which corresponded to the P250m-N250m was clearly identified, probably because activation of multiple areas generated large long-duration E E G potentials which were maximal around the vertex unlike M E G recordings.
[1] Kakigi R et al: Electroenceph Clin Neurophysiol, in press.
I PS-15-61 Pain-related magnetic fields following painful CO2 laser stimulation in man
IPS-15-4 1 Somatosensory evoked magnetic fields
Ryusuke Kakiqi, Sachiko Koyama, Minoru Hoshiyama, Yoshihiro Kitamura, Motoko Shimojo, Shoko Watanabe.
following mechanical stimulation of the scalp in humans
Minoru Hoshiyama, Ryusuke Kakigi, Sachiko Koyama, Yoshihiro Kitamura, Motoko Shimojo, Shoko Watanabe.
Department of Integrative Physiology, National Institute for Physiological Sciences, Japan This is the first report on the brain responses following scalp stimulation in humans. Somatosensory evoked magnetic fields (SEFs) following mechanical stimulation by air-pressure-induced tapping applied to the forehead and occiput were examined in normal subjects. The equivalent current dipole (ECD) of the initial magnetic field, 1M, was identified in the primary somatosensory cortex (SI) in the hemisphere contralateral to the stimulation. It would be current source at the scalp area of Broadman's area 3b in SI, the posterior bank of the central sulcus, generated by the first branch of trigeminal nerve (forehead) or greater occipital nerve (occiput). No consistent ECD could be identified in the frontal, parietal, and occipital areas. The ECD position of 1M in SI following the scalp stimulation was close inferior to the hand area of the SI. The present results are consistent with the well-known somatotopic organization of S1. The ECD of the second magnetic field, 2M, was identified in bilateral second sensory cortices (SII) in the upper bank of the Sylvian fissure. There was no clear consistent difference between the ECD positions of 2M following scalp
Department of Integrative Physiology, National Institute for Physiological Sciences, Japan The initial somatosensory evoked magnetic fields following painful heat stimulation by CO2 laser beam (pain SEFs) applied to the upper and lower limb were investigated in normal subjects. The main deflections, "Pain M g ' and "Pain ME' following the arm and leg stimulation, respectively, were identified in the bilateral second sensory cortices (SII). Those responses could not be identified by recording the averaged electroencephalography (EEG). The onset latencies of Pain MA and Pain ML were approximately 150 and 200 msec, respectively. The equivalent current dipoles (ECDs) of pain SEFs were oriented primarily upper and anterior direction. No consistent ECD was found in the primary sensory cortex (SI) in each hemisphere. When the probe was centered around the Fz' (2 cm in front of Fz), Cz and Pz' (2 cm behind Pz) to investigate the detailed topography of the pain SEFs, no consistent ECD was identified. Though there is a possibility that ECDs generated in SI and other areas are radially-oriented which are not identified in the recording of magnetoencephalography (MEG), we consider that neurons in the bilateral SII are initially activated following painful heat stimulation, unlike tactile, vibratory or electrical stimulations, which generate ECDs in SI. [1] Kakigi R et al: Neuroscience Letters, in press.