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M Hoshiyama

Publications and source records attributed to M Hoshiyama.

At least 37 records · Page 2Linked to original sources
PubMed2000

Effects of distraction on pain-related somatosensory evoked magnetic fields and potentials following painful electrical stimulation.

We aimed to compare the effects of distraction on pain-related somatosensory evoked magnetic fields (pain SEF) following painful electrical stimulation with simultaneous recordings of evoked potentials (pain SEP). Painful electrical stimuli were applied to the right index finger of eleven healthy subjects. A table with 25 random two-digit numbers was shown to the subjects, who were asked to add 5 numbers of each line in their mind (calculation task) or to memorize the numbers (memorization task) during the recording. In the SEF recording, 3 short-latency components within 50 ms of the stimulation were generated in the primary sensory cortex (SI) of the hemisphere contralateral to the stimulated finger. Middle-latency components between 100 and 250 ms after the stimuli were recorded from the secondary somatosensory cortex (SII) in the bilateral hemispheres or the cingulate cortex. No SEF components were significantly affected by either task. In the SEP recording, the middle-latency components (N140 and P230) were identified as being maximal around the vertex. Amplitudes of the N140 and P230 were not affected by each task, but the peak-to-peak amplitude (N140-P230) was significantly decreased by both the calculation and memorization tasks, particularly by the former. Subjective pain rating was decreased in both the calculation and memorization tasks, particularly in the former. We concluded that distraction tasks reduced activities in the limbic system, in which the middle-latency EEG component probably generated, while neither the short-latency SEF components generated in SI nor the primary pain-related SEF components generated in SII-insula are affected.

Adult↗
PubMed2000

Vibratory stimulation of proximal muscles does not affect cortical components of somatosensory evoked potential following distal nerve stimulation.

OBJECTIVES: The effects of the proprioceptive activity of the proximal muscles on somatosensory evoked potentials (SEPs) were investigated, using vibratory stimulation of proximal muscle tendons. METHODS: SEPs were recorded following electrical median nerve stimulation at the wrist during vibratory stimulation of tendon of pronator teres, biceps and trapezius muscles and fingers in 8 normal subjects. RESULTS: The cortical SEP components, N20, P25 and N33 recorded from the parietal area, and P20 and N30 recorded from frontal area contralateral to the stimulated side, were markedly attenuated by vibratory stimulation applied to the fingers, but unaffected by vibratory stimulation of the proximal muscles. CONCLUSION: The proprioceptive afferent, especially group Ia muscle spindle afferent, in the relaxed proximal muscles is not likely to contribute to the gating of SEP following distal nerve stimulation.

Brain↗
PubMed2000

Identification of auditory evoked potentials of one's own voice.

OBJECTIVE: We recorded vocalization related cortical potentials (VRCP) with complete masking of one's own voice, and separated the feedback auditory potentials following vocalization from the VRCP complex. METHODS: We used 9 right-handed healthy subjects. We recorded VRCP during simple vowel vocalizing under two conditions, (1) without masking (control); (2) with masking. Electroencephalography (EEG) was recorded from seven areas, Fz, Cz, Pz, C3, C4, T3 and T4, of the International 10-20 system. The trigger point was the onset of vocalized sound recorded through a microphone. RESULTS: In both control and masking conditions, similar negative potentials prior to the vocalization were observed. However, the amplitude just after the onset of vocalization was significantly smaller in the masking than the control condition. The difference waveform, obtained by subtracting the waveforms in the masking from those in the control condition, showed a simple negative peak after the vocalization onset. CONCLUSIONS: We considered that the difference waveform indicated the auditory evoked potentials following own voice in the auditory feedback process. Since there was no difference of the negative potentials before vocalization between the two conditions, we speculated that the masking effect on auditory feedback following vocalization was crucial, while its effect on the preparatory process of simple vocalization might be minimal.

Acoustic Stimulation↗
PubMed2000

Dermatome versus homunculus; detailed topography of the primary somatosensory cortex following trunk stimulation.

OBJECTIVE: Identification of a detailed topography of the receptive area for each of the thoracic dermatomes in humans using somatosensory evoked magnetic fields (SEF). METHODS: We analyzed the location of the equivalent current dipole (ECD) of SEF following electrical stimulation of the skin at Th4, Th6, Th8, Th10 and Th12 dermatomes in 14 normal subjects. RESULTS: Three deflections, M18, M25 and M40, were obtained within 60 ms of stimulation of Th6, Th8 and Th10 dermatomes. No consistent deflection could be identified following Th4 and Th12 dermatomal stimulation, probably due to a poor signal-to-noise ratio and difficulty in fixing the stimulation electrodes. M18 was absent or small in amplitude. The latency of M25 ranged from short to long in the order Th6, Th8 and Th10 (P<0.05). ECDs of all components for each site stimulation were located in the truncal area of the primary somatosensory cortex. Although the locations of the ECDs tend to be arranged from lateral to medial in the sequence Th6, Th8 and Th10, the difference was not significant. CONCLUSION: The representation area of the trunk is small, and the receptive areas for the stimulation of Th6, Th8 and Th10 dermatomes are considered to be very close or to overlap.

Adult↗
PubMed2000

After-effect of transcutaneous electrical nerve stimulation (TENS) on pain-related evoked potentials and magnetic fields in normal subjects.

OBJECTIVES: The after-effect of transcutaneous electrical nerve stimulation (TENS) on pain-related brain responses was investigated using electroencephalography (EEG) and magnetoencephalography (MEG). METHODS: We studied 13 healthy volunteers for the main experiment and 7 for the control experiment. The pain-related evoked cerebral potentials (PREP) at Cz and magnetic cortical fields (PRCF) on both hemispheres following painful electrical finger stimulation were simultaneously recorded before and after TENS on the right forearm of the median nerve territory at 50 Hz for 30 min. PREP and PRCF were similarly recorded without TENS in the control experiment. RESULTS: The PREP components, N150 and P220, were significantly attenuated after TENS, compared to those before TENS (P<0.01, two-way repeated ANOVA). However, there was no consistent change of the PRCF components. Eleven of 13 subjects reported no change of pain sensation after TENS. There was no change of PREP in control experiment without TENS. CONCLUSIONS: The results indicated that TENS reduced PREP following painful electrical stimulation, and that the origin of PREP was, at least partially, different from that of PRCF which was not changed after TENS. An after-effect of TENS significantly affected the generation process of PREP, but it was not enough to relieve the subjective painful feeling.

Adult↗
PubMed1999

Peripheral nerve conduction recorded by a micro gradiometer system (micro-SQUID) in humans.

We developed a new multi (twelve) -channel gradiometer system with the smallest and highest quality superconducting quantum interference device (micro-SQUID). A very small distance (3.80 mm) between the sensor coils and the skin provides quite high spatial resolution. The actual whole image of the sensory nerve action fields (NAF) of the human median nerve at the wrist were successfully recorded following digital nerve stimulation by using the micro-SQUID. The NAF showed the biphasic waveform at each of the 12 channels, and the isomagnetic field map clearly showed the moving quadrupole pattern. The quadrupole comprised a dipole for depolarization followed by another dipole with the opposite direction for repolarization. The polarized length of the nerve obtained by reconstructing the magnetic field maps was approximately 17 cm, and the magnetic field complex moved along the nerve from the distal to the proximal part of the wrist at 58.7 m/s.

Adult↗
PubMed1999

Changes of somatosensory evoked potentials during writing with the dominant and non-dominant hands.

Since close attention and special effort are necessary to perform difficult unskilled movements, particular brain activities underlying such movements could be expected to take place in the primary sensori-motor cortices (SI and MI). In this study we focused on such activities by analyzing the difference in the somatosensory evoked potential (SEP) in presence to the electrical stimulation of the median nerve during writing using the dominant and non-dominant hands in twelve right-handed and eight left-handed normal subjects. By alternately stimulating the right and left median nerves during the writing with either hand, SEPs were recorded from both hemispheres. During the dominant hand writing, the middle latency SEP components, i.e., parietal P25 and N33 and frontal N30, were significantly attenuated only in the hemisphere contralateral to the writing hand, corresponding to the conventional gating effect. During the non-dominant hand writing, not only those components recorded from the hemisphere contralateral to the writing hand, but also those from the hemisphere ipsilateral to the writing hand were significantly attenuated. In addition, N20 in the hemisphere contralateral to the writing hand was also significantly attenuated. There was no significant difference in the attenuation between the right-handed and left-handed subjects. The results indicated that the specific interaction between the signals after electrical stimulation and the sensory cortical activities related to the writing using the non-dominant hand occurred in both hemispheres, while it was recognized only in the hemisphere contralateral to the writing hand during the dominant hand writing. We speculate that the somatosensory cortex was more activated and thus interacted with the applied stimulation during the unskilled movement of the non-dominant hand compared to the movement of the dominant hand.

Adult↗
PubMed1999

Topography of the secondary somatosensory cortex in humans: a magnetoencephalo-graphic study.

The topography of the secondary somatosensory cortex (SII) responses to somatosensory stimulation applied to various parts of the body of normal volunteers was analyzed using magnetoencephalography (MEG). Although there were large inter-individual differences, the following orders of a location of equivalent current dipoles (ECDs) were found; (1) Anterior-posterior direction: lower lip-upper lip-thumb-middle finger-foot, (2) Medial-lateral direction: foot-middle finger-thumb-upper lip-lower lip, and (3) Lower-upper direction: lower lip-upper-lip-thumb-middle finger-foot. In general, these findings are similar to those obtained in studies of monkeys. However, the differentiation was not as clear as that seen in the homunculus in the primary somatosensory cortex (SI). The auditory cortex is located at a site more posterior, lateral and lower than the SII.

Adult↗
PubMed1999

Structure of the auditory evoked magnetic fields during sleep.

We studied the effects of sleep on auditory evoked magnetic fields following pure tone stimulation applied to the right ear of 10 healthy normal volunteers to investigate the changes in the processing of auditory perception in the primary auditory cortex. Dual 37-channel biomagnetometers were used to record auditory evoked magnetic fields over the bilateral temporal lobes in response to presented tones. Auditory evoked magnetic fields were compared for three stimulus frequencies (250, 1000 and 4000 Hz) and three sleep stages (awake state, sleep stages 1 and 2). Four main components, M50, M100, M150 and M200, were identified with latencies of approximately 50, 100, 150 and 200 ms, respectively. The latency of each component had a tendency to be prolonged with the depth of sleep stage in all frequencies. The amplitude ratios of the early-latency components (M50 and M100) showed a tendency of reduction compared with the same components in the awake state. By contrast, the amplitude ratios of the long-latency components (M150 and M200) were significantly enhanced with an increase in the sleep stage compared with the same components in the awake state. The equivalent current dipoles of all components in all conditions were detected at the superior temporal cortex (the primary auditory cortex). As for the changes in the equivalent current dipole location of each component, the equivalent current dipole was detected in the more posterior and medial region in responses to the high-frequency tone (1000 and 4000 Hz) compared with those to 250 Hz tone stimulation. Although the equivalent current dipoles of the early-latency components (M50 and M100) were in regions more anterior and superior compared to those in the awake state, there was no consistent tendency of changes in equivalent current dipole locations between each sleep stage in the late-latency components (M150 and M200). These findings are probably due to the difference in generating mechanisms between the early- and late-latency components.

Acoustic Stimulation↗
PubMed1999

Shortening of the cortical silent period following transcranial magnetic brain stimulation during an experimental paradigm for generating contingent negative variation (CNV).

OBJECTIVES: We investigated changes in the cortical silent period (CSP) following transcranial magnetic cortical stimulation (TCMS) during a standard paradigm which was designed to evoke contingent negative variation (CNV) in ten normal subjects. METHODS: We recorded the motor evoked potentials (MEP) and CSP during the inter-stimulus interval (ISI) of a CNV paradigm in ten normal subjects. The CNV paradigm consisted of a visual warning stimulus (S1) followed by a visual response stimulus (S2). The CSP following TCMS on the hand motor area was recorded from mildly contracted first dorsal interosseous muscles. RESULTS: The CSP was significantly shortened during the ISI (P < 0.01, t test) with a highly significant correlation with the TCMS timing during the ISI (P < 0.02, Spearman's correlation coefficient), while the MEP amplitude and latency were unchanged. CONCLUSIONS: The results suggested that shortening of the CSP was associated with neural processes related to preparation for voluntary movement during the paradigm.

Adult↗
PubMed1998

Reading of Japanese Kanji (morphograms) and Kana (syllabograms): a magnetoencephalographic study.

Magnetoencephalograms were recorded from six healthy Japanese subjects in order to investigate the areas in the cortices which are involved in the recognition of Japanese characters (Kanji and Kana). Forty-four Kanji (morphograms), 44 Kana (syllabograms) and 20 alphabet letters were used as stimuli. They were presented randomly and the subjects were required to read each stimulus and count the number of letters. The magnetic responses were recorded with dual 37-channel SQUID (Superconducting Quantum Interference Device) gradiometers from the temporal, parietal and occipital areas of the brain. The magnetic responses to Kanji and Kana were similar and consequently the locations of equivalent current dipoles (ECDs) to Kanji and those to Kana did not differ at any recording site. In all the subjects, ECDs were found in the posterior inferior temporal (PIT) areas approximately corresponding to Brodmann area 37 in the latency range of 150-300 msec. These activities were found in both hemispheres without consistent laterality. The location of the ECD moved forward from posterior to anterior in the PIT area as the latency increased in all but one subject. Only one subject showed activities in the left angular gyrus. Since activities in PIT areas were also found in alphabet letters, the bilateral PIT areas are considered to play an essential role in reading.

Adult↗
PubMed1998

Changes of somatosensory evoked potentials preceding rapid voluntary movement in Go/No-go choice reaction time task.

To elucidate the sensorimotor mechanisms in preparation of voluntary movement, we examined the changes of the somatosensory evoked potentials (SEPs) following median nerve stimulation in Go/No-go choice-reaction time task. Eleven normal subjects performed extension of the middle finger according to the Go signal while they did not make any movement and relaxed on the No-go and Control signals, respectively. Each signal was randomly presented on a computer screen in front of the subject. Single pulse stimulation was applied to the right median nerve at 150 ms after the response signal in each Go/No-go and Control sequence so as to be just before the voluntary movement in the Go sequence. The SEPs were recorded from F3, C3' (midpoint between P3 and C3) and P3 on the left hemisphere. In comparison with the Control sequence, the amplitude of N20 and P25 recorded from C3' and P3 was significantly attenuated before movement in the Go sequence (P<0.02, ANOVA with Bonferroni-Dunn post hoc procedure). On the other hand, the parietal N33 and frontal N30 were attenuated in both Go and No-go sequences (P<0.02). None of the SEP components were changed when the stimulus was delivered before the response signal. We speculate that the attenuation of N20 was linked with the activation of the motor cortex followed by the actual movement. The attenuation of other components up to 33 ms after stimulus were considered to be more related to the preparation or the attention to the voluntary movement than to the movement itself.

Adult↗
PubMed1998

Pain processing traced by magnetoencephalography in the human brain.

The temporal and spatial processing of pain perception in human was traced by magnetoencephalography (MEG). We applied a painful CO2 laser beam to the forearm of 11 normal subjects, and estimated the activated areas using a single equivalent current dipole (ECD) at each time point, and a brain electric source analysis (BESA) as a spatio-temporal multiple source analysis method. The four-source model was found to be the most appropriate; sources 1 and 2 at the secondary sensory cortex (SII) contralateral and ipsilateral to the stimulation, and sources 3 and 4 at the anterior medial temporal area (probably the amygdalar nuclei or hippocampal formation) contralateral and ipsilateral to the stimulation, respectively. Activities in all 4 areas were temporally overlapped. Activity in the primary sensory cortex (SI) contralateral to the stimulated site was not identified. Activity in the cingulate cortex was also not clearly identified. These results are probably due to one or more of the following factors; (1) the cingulate cortex is too deep, (2) the ECDs generated in the cingulate cortex are mainly oriented radially, and (3) the ECDs generated in bilateral hemispheres interfere with each other. No significant or consistent magnetic fields were recorded after 500 msec following the stimulation, probably due to the complicated spatial and temporal overlapping of activities in multiple areas.

Adult↗
PubMed1998

Visual evoked magnetic responses to central and peripheral stimulation: simultaneous VEP recordings.

Visual evoked magnetic field (VEF) and visual evoked potentials (VEP) in response to pattern reversal left half-field central (0-2 degrees, 0-5 degrees) and to left half-field peripheral stimulation (2-15 degrees, 5-15 degrees) were simultaneously recorded in 10 normal subjects. The aim was to localize the origin of the largest wave around 100 ms. By comparing the magnetic evoked 100m wave and electric evoked P100 wave, we found that the response to the small central field (0-2 degrees) stimulation was clearly evident in the VEP and not in the VEF, while the response to the peripheral field (2-15 degrees, 5-15 degrees) stimulation was clearly present in both the VEP and VEF. Our findings show that in contrast to the already recognized predominantly macular origin of VEP activity, VEF activity has a peripheral rather than macular prevalence. Our VEF findings are related to the retinotopic organization of the visual cortex; the 100m dipole to the central field (0-5 degrees) was localized more (1.04 +/- 0.84 cm) posterior than was the 100m dipole to peripheral stimulation (5-15 degrees). The localization of 100m dipoles superimposed on magnetic resonance images (MRI) to central stimuli showed interindividual variations that were in agreement with the known variability of the central field representation in the striate cortex: on the convexity of the occipital pole, in the outer surface of the occipital lobe, and around the calcarine fissure of the right hemisphere. In contrast, following peripheral stimulation, the 100m dipole was located along the medial surface of the hemisphere or in the calcarine fissure. Our results suggest that the main origin of the largest wave around l00ms in response to pattern reversal stimuli is in the striate cortex.

Adult↗
PubMed1998

[Cerebral embolism due to left atrial ball thrombus without mitral stenosis--usefulness of the transesophageal echocardiography for the diagnosis].

We reported two cases of cerebral embolism associated with atrial fibrillation. Left atrial ball thrombus without mitral stenosis was diagnosed by the transesophageal echocardiography, followed by successful removal. Left atrial ball thrombus has a risk for lethal complications, and a high incidence of systemic embolism even during anticoagulation therapy. An immediate surgical treatment is needed. The transthoracic echocardiography is not useful in diagnosis for left atrial ball thrombus. It is important to examine left atrial ball thrombus by the transesophageal echocardiography in patients with cerebral embolism associated with atrial fibrillation.

Atrial Fibrillation↗
PubMed1997

Pain-related somatosensory evoked magnetic fields following lower limb stimulation.

Somatosensory evoked magnetic fields (SEFs) following painful electrical stimulation of the sural nerve were examined in 6 normal subjects. Equivalent current dipoles (ECDs) of the deflections shorter than 100 ms in latency were located in the foot area of the primary sensory cortex (SI) in the contralateral hemisphere following both weak and painful stimulations. Two main deflections, N150m-P150m and N250m-P250m, were independently identified only following painful stimulation. ECDs of the N150m-P150m were considered to be located in bilateral second sensory cortices (SII). ECDs of the N250m-P250m were identified in multiple areas including bilateral cingulate cortices and SII. These findings were consistent with the pain-related SEFs following upper limb stimulation. Therefore, we considered that bilateral SII and the cingulate cortices were activated by the painful stimulation and that pain-specific brain activities in those areas did not depend on the stimulation site.

Adult↗