Biomedical subjects

M Hoshiyama

Publications and source records attributed to M Hoshiyama.

At least 19 recordsLinked to original sources

PubMed2005

Backward-masking: the effect of the duration of the second stimulus on recognition of the first stimulus.

OBJECTIVE: We recorded event-related magnetic fields following a target stimulus followed by a masking stimulus to investigate the visual backward masking effect using a helmet-type magnetoencephalography system in humans. METHODS: In the target stimulus with masking stimulus conditions, duration of the target stimulus was constant at 16 ms, and duration of the masking stimulus was altered (16, 48 and 144 ms). The target stimulus was masked by the 144-ms masking stimulus, but not by the 16-ms masking stimulus, and was obscured by the 48-ms masking stimulus. For control conditions (Single-condition), event-related magnetic fields were recorded following the sole presentation of the masking stimulus for 32, 64 or 160 ms. RESULTS: One major response was obtained at 180 ms after the onset of the stimulation in each condition. The equivalent current dipole of one major response was estimated to lie in the occipital lobe, but there was a relatively large inter-individual difference. There was no significant difference in latency between the target stimulus with masking stimulus conditions and Single-conditions. In the target stimulus with masking stimulus conditions with the 48- and 144-ms masking stimulus, the root mean square value did not differ from that in the respective Single-condition, while the root mean square value for the target stimulus with masking stimulus conditions with the 16-ms masking stimulus was significantly smaller than that in the Single-condition with the 32-ms masking stimulus, but not different from that in the Single-condition with the 16-ms masking stimulus. CONCLUSIONS: The peak latency of one major response depended on the onset of the first stimulus for both the target stimulus with masking stimulus conditions and Single-condition, but the root mean square value depended on the duration of the masking stimulus. We concluded that the temporal information for the target stimulus was preserved during the masking effect, while the figural information was interrupted by the masking stimulus. Our results suggested that temporal factors for the stimulus were processed differently from those responsible for the object's recognition during backward masking.

Brain↗

PubMed2004

Facilitation of A[delta]-fiber-mediated acute pain by repetitive transcranial magnetic stimulation.

BACKGROUND: Repetitive transcranial magnetic stimulation (rTMS) of the motor cortex modulates acute and chronic pain perception. The authors previously showed that rTMS over the primary motor cortex (M1) inhibited capsaicin-induced acute pain ascending through C-fibers. OBJECTIVE: To investigate the effects of 1-Hz rTMS over M1 on acute experimentally induced pain mediated by Adelta-fibers (i.e., another type of acute pain). METHODS: The authors examined whether rTMS over M1 affected laser evoked potentials (LEPs) in 13 normal subjects using thulium: yttrium-aluminum-garnet laser stimulation. Subjective pain-rating scores and LEPs obtained under three different conditions--rTMS, realistic sham stimulation, and a control condition with no stimulation--were compared. RESULTS: The authors found that 1-Hz rTMS over M1 significantly aggravated the subjective pain and enhanced the N2-P2 amplitudes compared with the sham or control sessions. Because the pain-rating scores and the N2-P2 amplitudes correlated positively, the N2-P2 amplitudes in the present study can be regarded as the cortical correlate of subjective pain. CONCLUSIONS: Together with the authors' previous study on C-fiber pain, this facilitatory effect of repetitive transcranial magnetic stimulation on Adelta-fiber-mediated further strengthens the notion of a relationship between repetitive transcranial magnetic stimulation over M1 and pain perception.

Acute Disease↗

PubMed2003

A comparative magnetoencephalographic study of cortical activations evoked by noxious and innocuous somatosensory stimulations.

We recorded somatosensory-evoked magnetic fields and potentials produced by painful intra-epidermal stimulation (ES) and non-painful transcutaneous electrical stimulation (TS) applied to the left hand in 12 healthy volunteers to compare cortical responses to noxious and innocuous somatosensory stimulations. Our results revealed that cortical processing following noxious and innocuous stimulations was strikingly similar except that the former was delayed approximately 60 ms relative to the latter, which was well explained by a difference in peripheral conduction velocity mediating noxious (Adelta fiber) and innocuous (Abeta fiber) inputs. The first cortical activity evoked by both ES and TS was in the primary somatosensory cortex (SI) in the hemisphere contralateral to the stimulated side. The following activities were in the bilateral secondary somatosensory cortex (SII), insular cortex, cingulate cortex, anterior medial temporal area and ipsilateral SI. The source locations did not differ between the two stimulus modalities except that the dipole for insular activity following ES was located more anterior to that following TS. Both ES and TS evoked vertex potentials consisting of a negativity followed by a positivity at a latency of 202 and 304 ms, and 134 and 243 ms, respectively. The time course of the vertex potential corresponded to that of the activity of the medial temporal area. Our results suggested that cortical processing was similar between noxious and innocuous stimulation in SI and SII, but different in insular cortex. Our data also implied that activities in the amygdala/hippocampal formation represented common effects of noxious and tactile stimulations.

Adult↗

PubMed2003

Electrical-induced pain diminishes somatosensory evoked magnetic cortical fields.

OBJECTIVE: To investigate the effect of conditioning painful stimulation on the early somatosensory magnetic fields (SEF) of test stimulation, in order to clarify the location of the gating effect of pain on tactile response. METHODS: We used a conditioning stimulus (CS) and test stimulus (TS) paradigm. The CS was applied at the left index finger followed by the TS at the left median nerve. The interstimulus interval between the CS and TS was varied from 100 to 1000 ms. There were two sessions corresponding to two intensities of the CS, painful CS (PCS) and non-painful CS (NPCS). Early components of SEF recorded 20 (1M) and 30 ms (2M) following the TS and the components obtained 20 (1m) and 30 ms (2m) following the CS were analyzed. Each value was compared between the two sessions. RESULTS: PCS and NPCS attenuated the response of the 2M but not the 1M. The effect of PCS was significantly stronger and lasted longer than that of NPCS. The 1m and 2m components did not differ between PCS and NPCS in terms of amplitude and latency. CONCLUSIONS: Our data indicated that the early components of the median nerve SEF were affected by a preceding painful stimulation much more than a non-painful stimulus given on the median nerve, and that the sensory gating effect of a painful stimulation on tactile sensation lasted longer than that of a non-painful stimulation. Furthermore, our findings suggested the existence of a 'touch gate' (effect of pain on tactile sensation) at the level of the thalamus or primary somatosensory cortex (SI). SIGNIFICANCE: The finding suggested that the touch gate might lie in the thalamus or SI.

Adult↗

PubMed2003

Effect of tactile interference stimulation of the ear in human primary somatosensory cortex: a magnetoencephalographic study.

OBJECTIVE: To confirm the somatotopic representation of the ear in the primary somatosensory cortex (SI), we studied the tactile interference effects on somatosensory evoked magnetic fields (SEFs) following stimulation of the ear (Helix, Lobulus and Tragus). METHODS: We applied tactile interference stimulation to the neck or face area continuously and concurrently while a time-locked electrical stimulation was applied to the ear. If the amplitude would be reduced by the interference, this would indicate that the cortical representation for both the time-locked electrical stimulation and the continuous interference stimulation overlapped. A two or 3-source model, Source 1 in the neck area of SI, Source 2 in the face area of SI, and Source 3 in the secondary somatosensory cortex (SII), was found to be the most appropriate by brain electric source analysis (BESA). RESULTS: Amplitudes of Sources 1 and 2 in most interference conditions were decreased. Source 1 following stimulation of all 3 sites was significantly reduced when the interference was applied to the neck area. Source 2 following stimulation of all 3 sites was significantly reduced when the interference was applied to the face area. CONCLUSIONS: These findings showed that the interference effect was found in both the neck and face areas of SI following the ear stimulation. SIGNIFICANCE: The representation of the ear in SI might be located in both the neck and face areas.

Adult↗

PubMed2002

Cerebral activation by the signals ascending through unmyelinated C-fibers in humans: a magnetoencephalographic study.

Cerebral processing of first pain, associated with A delta-fibers, has been studied intensively, but the cerebral processing associated with unmyelinated C-fibers, relating to second pain, remains to be investigated. This is the first study to clarify the primary cortical processing of second pain by magnetoencephalography, through the selective activation of C-fibers, by the stimulation of a tiny area of skin with a CO2 laser. In the hemisphere contralateral to the side stimulated, a one-source generator in the upper bank of the Sylvian fissure (secondary somatosensory cortex, SII) or two-source generators in SII and the hand area of the primary somatosensory cortex (SI) were the optimal configurations for the first component 1M. The onset and peak latency of the two sources in SI and SII were not significantly different. In the hemisphere ipsilateral to the stimulation, only one source was estimated in SII, and its peak latency was significantly (approximately 18 ms on average) longer than that of the SII source in the contralateral hemisphere. From our findings we suggest that parallel activation of SI and SII contralateral to the stimulation represents the first step in the cortical processing of C-fiber-related activities, probably related to second pain.

Adult↗

PubMed2001

Correspondence between short-latency somatosensory evoked brain potentials and cortical magnetic fields following median nerve stimulation.

We investigated the somatosensory evoked cortical magnetic field (SEF) components corresponding to the somatosensory evoked potential (SEP) components between 20 and 30 ms after median nerve stimulation. SEP and SEF were simultaneously recorded after right median nerve stimulation in seven healthy subjects. Twenty single-sweep epochs of SEF and SEP were selected, in which the first SEF component at 20 ms, 1M, and the second component at 30 ms, 2M, were identifiable. The selected epochs were re-averaged at the peaks of 1M and 2M as the triggering periods (zero ms). The width of the deflection, the temporal dispersion (TD), of SEP components, P20 and N30 (Fz-A2), N20, cP25 and cN30 (C3-Fz), N20 and pP30 (P3-A2), and N20 and P30 (P3-Fz), were compared between three averaging conditions. The N20/P20 components showed significantly smaller TDs when the epochs were averaged at the 1M peak (one-way factorial ANOVA, P<0.02) than those of the control, but averaging at the 1M peak did not decrease the TD of N30/P30. On averaging at the 2M peak, the TDs of N30/P30 components recorded from Fz-A2 and P3-Fz were smaller than those of the control. Neither the averaging at the 1M peak nor that at the 2M peak decreased the TD of the cP25 and cN30 components. Source analysis showed that the equivalent current dipoles (ECDs) for both 1M and 2M were located around the central sulcus, possibly in the primary somatosensory cortex (SI). We confirmed that the 1M and 2M temporally linked with N20/P20 and N30/P30, respectively. The difference of TD of N20/P20 and N30/P30 indicated that the neural pathways to the responses to N20/P20 and N30/P30 might be independent.

Adult↗

PubMed2001

Hearing the sound of silence: a magnetoencephalographic study.

We visualized the brain activity for retrieval imagery of a sound using dual 37-channel magnetometers in seven right-handed healthy subjects. A soundless video image of a hammer striking an anvil was presented on a screen. Significantly larger evoked magnetic fields were recorded, dominantly in the right hemisphere, in six subjects when they imagined the sound than when they did not. The initial peak of the response was 151.0 +/- 26.5 ms (mean +/- s.d.) after the blow. Equivalent current dipoles (ECDs) for the responses recorded from the right hemisphere were located around the inferior frontal sulcus in three subjects and in the insular region in three subjects, but reliable ECDs were not estimated from the left hemisphere. The results suggested that the initial activity for sound retrieval imagery appeared around the inferior frontal and insular areas, dominantly in the right hemisphere.

Adult↗

PubMed2001

A new method for measuring the conduction velocities of Abeta-, Adelta- and C-fibers following electric and CO(2) laser stimulation in humans.

The conduction velocities of Abeta-, Adelta- and C-fibers of a peripheral nerve of the upper limb in normal subjects were measured by a combination of conventional electric stimulation, painful CO(2) laser stimulation and non-painful CO(2) laser stimulation of a tiny skin surface area, respectively. The values obtained were 69.1+/-7.4 m/s, 10.6+/-2.1 and 1.2+/-0.2 m/s, respectively. These findings demonstrated that the combined methods are useful for experimental and clinical exploration of the physiological function and pathophysiological role of Abeta-, Adelta- and C-fibers of a given peripheral nerve.

Adult↗

PubMed2001

Representation of the ear in human primary somatosensory cortex.

We studied 13 healthy subjects with a multichannel magnetoencephalography (MEG) system to investigate the somatotopic representation of the ear in the primary somatosensory cortex (SI). We stimulated three parts of the left ear: the helix, the lobulus, and the tragus. The somatosensory-evoked magnetic fields (SEFs) were successfully measured in 7 of 13 subjects. Short-latency responses were analyzed using both single dipole and multidipole models (brain electric source analysis, BESA). From the single dipole model, the equivalent current dipole (ECD) following the helix stimulation was estimated to be near the neck area of SI in all the subjects. In the lobulus stimulation, the ECDs were estimated around the neck area of SI in four subjects, in the face area in one subject, and in the deep white matter in two subjects. In the tragus stimulation, the ECDs were estimated around the neck area of SI in three subjects, in the hand area of SI in two subjects, and in the deep white matter in two subjects. When the ECDs were estimated to be located in unlikely sites (hand area and deep white matter), a two-dipole model, (1) the neck area of SI and (2) face area of SI, was found to be the most appropriate. Although this might be a preliminary study due to a relatively small number of subjects, it revealed that receptive fields of some part of the ear, such as the lobulus and tragus, might be present in both the neck and face areas of SI. These findings suggested that the "ear area" of SI has variability between subjects, unlike the other areas of SI, possibly because the ear is located on the border between the neck and face.

Adult↗

PubMed2001

Neural activities during Wisconsin Card Sorting Test--MEG observation.

The present study recorded activities of magnetoencephalography (MEG) to the presentation of cards, and to the presentation of feedback signals in 12 normal subjects while they performed the Wisconsin Card Sorting Test (WCST), to observe temporal and spatial processing during the task. The MEG responses were compared between two different conditions in the presentation both of cards and of feedback signals: the cards proceeded by the first wrong [W1st(C)] and by the 4th correct feedback signals [C4th(C)]; and the feedback of the first wrong [W1st(FB)] and the 4th correct signals [C4th(FB)]. A multi-dipole model, brain electric source analysis (BESA), was used to explore the dipole sources responsible for the MEG activities. We found that MEG activity differences between the W1st(C) and the C4th(C) condition occurred in the period of 190-220 ms (M190 and M200), and 300-440 ms (M300 and M370) mainly at the supramarginal gyrus, the dorsolateral prefrontal, and the middle and inferior frontal gyrus. MEG differences between the W1st(FB) and the C4th(FB) condition occurred 460-640 ms (M460) after the presentation of the feedback signals, with the activation of the dorsolateral prefrontal cortex and the middle frontal cortex. No significant location differences were found between the frontal responses (M370) of the W1st(C) and M460 of the W1st(FB). Our results proved that the WCST task activates a broad frontal area and the parieto-frontal network across time streaming. Both shifting attention to the wrong feedback and enhanced visual working memory to the sorting shifting condition of the card presentation occur in the same areas at different time points.

Adult↗

PubMed2001

Auditory response following vocalization: a magnetoencephalographic study.

OBJECTIVE: We recorded vocalization-related cortical fields (VRCF) under complete masking of a subject's own voice to identify the auditory component evoked by a subject's own voice in the VRCF complex. METHODS: We recorded VRCF during simple vowel (/u/) vocalization in 10 right-handed healthy volunteers under two conditions: (1) no masking (control) and (2) masking of the subject's own voice by weighted-white noise during vocalization. In the second experiment, we recorded auditory evoked magnetic fields (AEF) following stimulation of a speech sound applied by voice-recorder. RESULTS: The onset of VRCF appeared gradually before the vocalization onset, and a clear phase-reversed deflection was identified after the onset of vocalization. The difference waveform obtained by subtracting the VRCF of the masking condition from that of the control showed a deflection (1M) at 81.3+/-20.5 (mean+/-SD) ms after the onset of vocalization, but there was no consistent deflection before the vocalization onset. The AEF following voice sound in the second experiment showed the M100 component at 94.3+/-18.4 ms. The equivalent current dipole of the 1M component for different waveforms was located close in the auditory cortex to that of the M100 for AEF waveforms in each hemisphere. CONCLUSION: We successfully separated the auditory feedback response from the VRCF complex, using an adequate masking condition during vocalization of a subject's own voice. The masking effect was crucial to the auditory feedback process after the onset of vocalization. The present results suggested that the 1M component was mainly generated from the auditory feedback process by the subject's own voice. The activated auditory area for simple own voice might be similar to that for simple external sound.

Adult↗

PubMed2001

Two evoked responses with different recovery functions in the primary somatosensory cortex in humans.

OBJECTIVES: We investigated the recovery function of somatosensory evoked magnetic cortical fields (SEFs) to confirm the temporal aspects of the somatosensory process in humans. METHODS: SEFs were recorded following median nerve electrical stimulation in 6 healthy subjects. Double stimulation, with interstimulus intervals (ISIs) from 3 to 100 ms, was applied, and the SEF components for the second stimulation were analyzed. In a supplementary experiment, responses to single stimulations of various intensities from the sensory threshold to the motor threshold were studied. RESULTS: The first SEF component (1M) diminished when the ISI was less than 10 ms, while the second component (2M) remained even when the ISI was 3 ms. The two components showed a very similar attenuation with decrease of stimulus intensity. There was no significant difference in dipole location between 1M and 2M in the primary somatosensory cortex (SI). CONCLUSIONS: The results suggested that at least two independent pathways with different recovery functions exist in a similar area in the SI.

Adult↗

PubMed2001

Effects of attention on pattern-reversal visual evoked potentials: foveal field stimulation versus peripheral field stimulation.

The effects of foveal field attention on pattern reversal visual evoked potential (VEP) were investigated in thirteen normal subjects. Conventional monocular VEP was recorded during the three conditions of control, foveal concentration and reaction time task. Three patterns of checker-board, which were full field (radius, 0-9 degrees), peripheral field (2.5-9 degrees) and foveal field (0-2.5 degrees), were presented for the stimulation in each condition. The P100 and N145 amplitude of the peripheral field VEP were significantly smaller during the concentration and the reaction time task conditions that that in the control session, while the foveal field VEP amplitudes were enhanced in the concentration and reaction time tasks conditions. The full field VEP amplitudes were not significantly changed by the conditions. We concluded that the act of concentration to the foveal field or the task requiring attention to the foveal field, enhanced the VEP response to foveal field stimulation and suppressed the VEP to the peripheral field. A gating effect in area V1 was speculated, although extra-striate cortex might contribute.

Adult↗

PubMed2001

A unique area of the homonculus: the topography of the primary somatosensory cortex in humans following posterior scalp and shoulder stimulation.

We recorded somatosensory evoked magnetic field (SEF) to investigate the differentiation in the receptive area for the face, lower part of the posterior scalp (mastoid) and shoulder, which occupy an unique area in the homunculus. We analyzed the location of the equivalent current dipole (ECD) of SEF following electrical stimulation of the skin at the face, mastoid and shoulder in 20 normal subjects. Three deflections (1M, 2M and 3M) were obtained within 50 ms of the stimulation in 16 of 20 subjects. The peak latency of the 1M and 2M was not significantly different at any stimulus sites. The amplitude of the 1M was significantly larger following the face than mastoid stimulation (p<0.05). The 16 subjects were classified according to the locations of the ECD on stimulation of the mastoid: close to that for shoulder stimulation, but significantly (p<0.05) more superior and medial to that following the face stimulation (Type 1, eleven subjects); close to that for face stimulation, but significantly (P<0.05) more inferior and lateral to that following the shoulder stimulation (Type 2, five subjects). The site of the receptive area for the posterior scalp shows interindividual variation, possibly due to anatomical differences.

Adult↗

PubMed2000

Effects of check size on pattern reversal visual evoked magnetic field and potential.

The effects of different check sizes on the 100m component of pattern reversal visual evoked magnetic fields (VEF) and the P100 component of visual evoked potentials (VEP) in terms of latency, amplitude and source localization were analyzed. Half field stimuli with or without central occlusion with check sizes of 15', 30', 60', 90' and 180' of visual arc were given to 7 healthy subjects. VEF and VEP were recorded simultaneously. The effect of the check size on the peak latency of both 100m and P100 was significant (P<0.01, ANOVA). The latencies for the smaller checks were significantly longer than those for the larger checks. The effect of the check size on the amplitude of the 100m to the stimulation with central occlusion was significant (P<0.05, ANOVA), but was not to the stimulation without central occlusion. That is, the amplitudes for the smaller checks were significantly smaller than those for the larger checks when using the stimulation with central occlusion, but not the stimulation without central occlusion. The effect of the check size on the P100 amplitude was not significant to the stimulation with and without central occlusion. The equivalent current dipoles were located around the calcarine fissure and did not differ significantly in location with check size. In conclusion, check size significantly affects the latency and amplitude of the 100m and/or P100, but not the receptive areas for the stimulation.

Adult↗

PubMed2000

The somatosensory evoked magnetic fields.

Averaged magnetoencephalography (MEG) following somatosensory stimulation, somatosensory evoked magnetic field(s) (SEF), in humans are reviewed. The equivalent current dipole(s) (ECD) of the primary and the following middle-latency components of SEF following electrical stimulation within 80-100 ms are estimated in area 3b of the primary somatosensory cortex (SI), the posterior bank of the central sulcus, in the hemisphere contralateral to the stimulated site. Their sites are generally compatible with the homunculus which was reported by Penfield using direct cortical stimulation during surgery. SEF to passive finger movement is generated in area 3a or 2 of SI, unlike with electrical stimulation. Long-latency components with peaks of approximately 80-120 ms are recorded in the bilateral hemispheres and their ECD are estimated in the secondary somatosensory cortex (SII) in the bilateral hemispheres. We also summarized (1) the gating effects on SEF by interference tactile stimulation or movement applied to the stimulus site, (2) clinical applications of SEF in the fields of neurosurgery and neurology and (3) cortical plasticity (reorganization) of the SI. SEF specific to painful stimulation is also recorded following painful stimulation by CO(2) laser beam. Pain-specific components are recorded over 150 ms after the stimulus and their ECD are estimated in the bilateral SII and the limbic system. We introduced a newly-developed multi (12)-channel gradiometer system with the smallest and highest quality superconducting quantum interference device (micro-SQUID) available to non-invasively detect the magnetic fields of a human peripheral nerve. Clear nerve action fields (NAFs) were consistently recorded from all subjects.

Brain Mapping↗

PubMed2000

Spatiotemporal source analysis of vocalization-associated magnetic fields.

The vocalization-related cortical fields (VRCF) following vowel vocalization were studied by magnetoencephalography (MEG) in eight normal subjects. A multiple-source model, BESA (Brain Electric Source Analysis), was applied to elucidate the generating mechanism of VRCF in the period from 150 ms before to 150 ms after the onset of vocalization. Six sources provided satisfactory solutions for VRCF activities during that period. Sources 1 and 2, which were activated from approximately 150 ms before the vocalization onset, were located in laryngeal motor areas of the left and right hemispheres, respectively. Sources 5 and 6 were located in the truncal motor area in each hemisphere, and they were very similar to sources 1 and 2 in terms of temporal change of activities. Sources 3 and 4 were located in the auditory cortices of the left and right hemispheres, respectively, and they appeared to be activated just after the vocalization onset. However, all six sources were temporally overlapped in the period approximately 0-100 ms after the vocalization onset. The present results suggested that the bilateral motor cortices, probably laryngeal and truncal areas, were activated just before the vocalization. We considered that the activities of the bilateral auditory areas after the vocalization were the response of the subject's central auditory system to his/her own voice. The motor and auditory activities were temporally overlapped, and BESA was very useful to separate the activities of each source.

Adult↗