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R Kakigi

Publications and source records attributed to R Kakigi.

At least 19 recordsLinked to original sources
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↗
PubMed1997

Human cortical area responding to stimuli in apparent motion.

Apparent motion is the perception of the realistic smooth motion of an object which flashes first at one place then at another. To investigate human cortical responses to stimuli in apparent motion, we used a multichannel biomagnetometer to record the magnetic fields evoked by these stimuli in four normal subjects. The results showed the presence of a localized cortical area exclusively sensitive to apparent motion stimuli that is identical to that for smooth motion. In three subjects this area corresponded to the human homologue of MT/V5. Moreover, the same region in the extrastriate cortex was involved in the short range (0.1 degree) apparent motion process as well as the long range (1.0 degree) process.

Adult↗
PubMed1997

Odorant evoked magnetic fields in humans.

We investigated the olfactory evoked magnetic fields (OEFs) in 14 normal subjects. Pulses of odorant air containing amyl acetate or phenethyl alcohol, and odorless air were administered to the subject through a nasal tube. A clear and consistent OEF component, 1M, was identified in all subjects, and a second component, 2M, was detected in seven subjects, but no consistent component was identified in response to the odorless air. The peak latencies of the 1M and 2M components were approximately 320 and 630 ms, respectively. The waveforms produced by the odorless air were subtracted from the waveforms produced by the odorant air to obtain the 'subtraction' waveform, which indicated the 1M and 2M component more clearly. Their equivalent current dipoles (ECDs) were estimated in the regions around the Sylvian fissure symmetrically in both hemispheres. Therefore, these areas are proposed to be involved in olfactory perception in humans.

Adult↗
PubMed1997

Effects of movement and movement imagery on somatosensory evoked magnetic fields following posterior tibial nerve stimulation.

We examined the "gating" effects caused by active and passive movements of toes and by "movement imagery" (mental moving of the toe without actual movements) on somatosensory evoked magnetic fields (SEFs) following stimulation of the posterior tibial nerve in normal subjects. Active and passive movements significantly attenuated the short- and middle-latency cortical components (P < 0.001) with no latency change, and the effects of the active movements were larger than those of the passive movements. In contrast, the subsequent long-latency component with a latency of about 100 ms was enhanced only by the active movements. Therefore, both centrifugal and centripetal mechanisms should be considered. The gating effects by movements on all components may occur in the primary sensory cortex (SI) in the hemisphere contralateral to the stimulated nerve, because all of the equivalent current dipoles (ECDs) of the components in the "control" and each "interference" waveform were located there. Active movements of the toes contralateral to the stimulated nerve caused no significant gating effect. The short-latency components were not consistently changed by "movement imagery", but the middle- and long-latency components were enhanced. Their ECDs were located in the SI contralateral to the stimulated nerve and in the SII in bilateral hemispheres. Therefore, we speculated that brain responses to somatosensory stimulation, particularly components generated in SII, were affected by volitional changes.

Adult↗
PubMed1996

Effects of tactile interference stimulation on somatosensory evoked magnetic fields.

Tactile stimulation of the hand interferes with somatosensory evoked brain responses following electrical median nerve stimulation. This effect was studied in eight normal subjects by magnetonecephalography (MEG). When stimulation was applied to the hand ipsilateral to the stimulated nerve, only the third response (3M) was enhanced in five subjects, but other responses were attenuated in all subjects. These interference effects were probably due to interactions in areas 3b and 1. After stimulation of the contralateral hand, only the second response (2M) was enhanced in six subjects. This effect was probably due to the intracerebral interactions mediated through the corpus callosum.

Adult↗
PubMed1996

Reciprocal change of motor evoked potentials preceding voluntary movement in humans.

Reciprocal change of motor evoked potentials (MEPs) recorded from the agonist and antagonist muscles of the forearm was studied in 10 normal subjects in whom transcranial magnetic stimulation (TMS) was applied to the hand motor area before voluntary wrist movements. MEP recorded from the agonist muscles, that is, radial extensor muscles for wrist extension and ulnar flexor muscle for wrist flexion, were gradually facilitated with shortening of the interval between the magnetic stimulation and the voluntary muscle contraction. In contrast, MEP recorded from the antagonist muscles, that is, ulnar flexor muscle for wrist extension and radial extensor muscles for wrist flexion, were gradually suppressed as the interval shortened. The reciprocal change of MEP was recognized when TMS was applied within 60 ms prior to the voluntary movements. The present data confirmed that reciprocal change of MEP was recognized before voluntary movements; they further suggest that cortically originated reciprocal control of the corticospinal pathway may exist and that it may be generated just before the voluntary movement.

Adult↗
PubMed1996

Clinical application of automatic integrative interpretation of awake background EEG: quantitative interpretation, report making, and detection of artifacts and reduced vigilance level.

Methods for the automatic detection of artifacts and vigilance level of the EEG record were developed for a preprocessing procedure for the automatic integrative interpretation of awake background EEG. All equations for the detection were derived such that they would conform to the procedure that an EEGer adopts for visual EEG inspection. The automatic EEG interpretation system was improved by adding the proposed preprocessing procedure and gave satisfactory interpretation results for the EEG data even contaminated with artifacts or in the drowsy state. The automatic EEG interpretation method proposed here is suggested for clinical use as an assistant tool for EEGers and physicians.

Arousal↗
PubMed1996

Somatosensory evoked magnetic fields following stimulation of the lip in humans.

The topography of somatosensory evoked magnetic fields (SEFs) following stimulation of the upper and lower lips was investigated in 6 normal subjects. When the lateral side of the upper lip was stimulated, P20m and its counterpart, N20m, were identified in the hemisphere contralateral to the stimulated side. The equivalent current dipoles (ECDs) of N20m-P20m were considered to be located in lip area of the primary sensory cortex (SI). Middle latency deflections (N40m-P40m, N60m-P60m, and N80m-P80m) were identified in bilateral hemispheres. Their ECDs were located in the SI in both hemispheres. Long latency deflections (P110m-N110m) were recognized in both hemispheres, and their ECDs were located inferior to the SI, in an area considered to be the secondary sensory cortex (SII). When the midline of the lip was stimulated, similar short and middle latency deflections was also identified, but SII deflections (P110m-N110m) were decreased in amplitude. When the lower lip was stimulated, the ECDs of short and middle latency deflections were located at a site in the SI inferior to or near those elicited by upper lip stimulation. The ECDs of P110m-N110m were located in an area of the SII similar to that upon stimulation of the upper lip, but their orientations were different.

Adult↗
PubMed1996

Effects of noxious cooling of the skin on pain perception in man.

By means of somatosensory evoked brain potentials following painful CO2 laser stimulation (pain SEPs) and a pain visual analogue scale (VAS), we investigated changes in pain perception caused by noxious cooling of the skin in normal subjects. Pain SEPs were recorded from scalp electrodes following laser stimulation applied to the leg under various conditions as follows: (1) control (without any interference); (2) 46 degrees C foot (dipping the foot ipsilateral to the stimulated leg in hot water at 46 degrees C); (3) 0 degrees C foot (dipping the foot ipsilateral to the stimulated leg in ice water at 0 degrees C); and (4) 0 degrees C hand (dipping the hand contralateral to the stimulated leg in ice water at 0 degrees C). Marked decreases in amplitude of pain SEPs and VAS were observed under all conditions as compared with the control (P < 0.001); the degree of pain relief was significantly correlated with changes in pain SEPs. These changes were greatest in the '0 degrees C hand' condition, followed in decreasing order by '0 degrees C foot' and '46 degrees C foot', and there was a significant difference between '0 degrees C hand' and the '46 degrees C foot' condition. We considered that the decrease in pain is due to the diffuse noxious inhibitory control (DNIC). The reason why the degree of pain relief in '0 degrees C foot' condition was less than that in '0 degrees C hand' condition is unclear, but some particular spatial summation of two kinds of nociceptive impulses mediated by the same pathway might take place.

Adult↗
PubMed1996

Intracerebral interactions caused by bilateral median nerve stimulation in man: a magnetoencephalographic study.

Somatosensory evoked magnetic fields (SEFs) following stimulation of the median nerves bilaterally ('bilateral' waveform) were examined in normal subjects to determine the interference effects of activation of sensory areas in bilateral hemispheres. SEFs following right median nerve stimulation and those following left median nerve stimulation were summated ('summated' waveform). A 'difference' waveform was induced by subtraction of the 'bilateral' waveform from 'summated' waveform. Short-latency deflections showed no consistent differences between the 'summated' and 'bilateral' waveforms, but the middle-latency deflection. N60m-P60m, in the 'bilateral' waveform was significantly (P < 0.01) smaller than that in the 'summated' waveform. The long-latency deflection, the N90m-P90m, in the 'bilateral' waveform was markedly (P < 0.001) reduced in amplitude as compared with the 'summated' waveform. The differences were clearly identified in the 'difference' waveform, in which the main deflections, U90m-D90m, were found in all subjects. Equivalent current dipoles (ECDs) of the short- and middle-latency deflections were located in the primary sensory cortex (SI) contralateral to the stimulated nerve, but ECDs of the N90m-P90m and U90m-D90m were located in bilateral second sensory cortices (SII) which are considered to receive ascending signals from bilateral sides of the body.

Adult↗
PubMed1996

Effects of judgement process on motor evoked potentials in Go/No-go hand movement task.

We examined the motor evoked potentials (MEP) of the forearm muscles following transcranial magnetic stimulation after the Go/No-go reaction-time hands movement in ten normal subjects. Facilitation of MEP of the agonistic muscles and suppression of MEP of the antagonistic muscles were recognized during the 'Go' session, while the MEPs of both muscles were markedly suppressed in the 'No-go' session. We considered that this MEP changes reflected the inhibition on the pyramidal tract during the 'No-go' session.

Adult↗
PubMed1996

Effects of sleep on somatosensory evoked responses in human: a magnetoencephalographic study.

We studied the effects of sleep on somatosensory evoked magnetic fields (SEFs) following median nerve stimulation in normal subjects, to investigate the changes of functional processing of sensory perception in the primary and second sensory cortices (SI and SII). The early components, 1M, 2M and 3M, which were generated in SI contralateral to the stimulated nerve, showed no significant change of latency or amplitude in stage 1 or 2 as compared with those in the awake state. The long-latency response, 4M whose latency was about 100 ms, was significantly enhanced in stage 2. The 4M was considered to be generated in SI and SII in the awake state, but the enhanced 4M in stage 2 was restricted in SI. The 4M(I) generated in SII of the hemisphere ipsilateral to the stimulated nerve, corresponding to 4M in the contralateral hemisphere, was absent during sleep. These findings were probably due to the difference of activities between SI and SII during sleep, that is, an increase of sensitivity to somatosensory stimulation in SI but a decrease or disappearance in SII.

Adult↗
PubMed1996

Differentiation of receptive fields in the sensory cortex following stimulation of various nerves of the lower limb in humans: a magnetoencephalographic study.

The authors investigated magnetoencephalography following stimulation of the posterior tibial (PT) and sural (SU) nerves at the ankle, the peroneal nerve (PE) at the knee, and the femoral nerve (FE) overlying the inguinal ligament in seven normal subjects (14 limbs) and confirmed its usefulness in clarifying the detailed differentiation of the receptive fields in the lower limb area of the primary sensory cortex in humans. The results were summarized as follows: 1) the equivalent current dipoles (ECDs) estimated by the magnetic fields following stimulation of the PT and SU were located very close to each other, along the interhemispheric fissure in all 14 limbs. They were directed horizontally to the hemisphere ipsilateral to the stimulated nerve. 2) The ECD following stimulation of the FE was clearly different from that seen in the other nerves, in terms of the location and/or direction, in all 14 limbs. The ECDs of 14 limbs were classified into two types according to the distance of ECD location between PT and FE; Type 1 (> 1 cm, nine limbs) and Type 2 (< 1 cm, five limbs). The ECD following FE stimulation was located on the crown of the postcentral gyrus or at the edge of the interhemispheric fissure in Type 1 and was close to the ECDs following PT and SU stimulation along the interhemispheric fissure in Type 2. 3) The ECD following PE stimulation was located along the interhemispheric fissure in all 14 limbs as for PT and SU. Its location was slightly but significantly higher than that of PT and SU in Type 1 and was close to ECDs following PT and SU stimulation in Type 2. The present findings indicated that approximately 65% (nine of 14) of the limbs showed the particular receptive fields compatible with the homunculus. Large inter- and the intraindividual (left-right) differences found in the present study indicated a significant anatomical variation in the area of the lower limb in the sensory cortex of humans.

Adult↗
PubMed1996

Recurrent demyelinating transverse myelitis in a high titer HBs-antigen carrier.

A 46-year-old man who was an extremely high titer hepatitis B surface (HBs)-antigen carrier had three attacks of acute demyelinating transverse myelitis associated with signs of meningeal irritation. Each episode showed good response to corticosteroid therapy. The cerebrospinal fluid was characterized by elevated levels of myelin basic protein (MBP) and predominating CD4+CD29+ helper-inducer T cells during the acute stages, and also by persistently positive HBs antigen. There were neither autoantibodies nor evidence of vasculitis. However, circulating immune complexes composed of HBs antigen disappeared after treatment, indicating that immunity to hepatitis B virus played a role in the demyelinative lesion formation in the central nervous system (CNS). In light of the animal studies demonstrating autoimmunity triggered by molecular mimicry between MBP and hepatitis B virus antigens, this patient may serve as a rare example of CNS demyelination in humans with the same autoimmune etiology.

Autoantigens↗
PubMed1995

Somatosensory evoked magnetic fields after mechanical stimulation of the scalp in humans.

Somatosensory evoked magnetic fields after mechanical stimulation by air-pressure-induced tapping which was applied to the forehead and occiput were examined in normal human 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. The ECD of the subsequent magnetic fields, 2M, was identified in bilateral second sensory cortices (SII). The ECD position of 1M in SI generated after the scalp stimulation was closely inferior to the hand area of the SI, which was consistent with the well-known somatotopic organization, 'homunculus'.

Adult↗
PubMed1995

Pain-related magnetic fields following painful CO2 laser stimulation in man.

The initial somatosensory evoked magnetic fields following painful heat stimulation by CO2 laser beam applied to the upper and lower limb were investigated in normal subjects. The main deflections, 'Pain MA' and 'Pain ML' following the arm and leg stimulation, respectively, were identified in the bilateral second sensory cortices (SII). The onset latencies of Pain MA and Pain ML were approximately 150 and 200 ms, respectively. No consistent equivalent current dipole was found in other areas including the primary sensory cortex in each hemisphere. Therefore, we consider that neurons in the bilateral SII are initially activated following painful heat stimulation.

Adult↗