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Biomedical subjects

H Shibasaki

Publications and source records attributed to H Shibasaki.

At least 91 records · Page 5Linked to original sources
PubMed2000

Role of primary sensorimotor cortices in generating inhibitory motor response in humans.

To clarify the mechanism by which inhibitory motor responses such as cortical negative myoclonus are generated in humans, three patients with medically intractable partial epilepsy (two with frontal lobe epilepsy and one with parietal lobe epilepsy) were studied by means of direct cortical stimulation with a single electric pulse through subdural electrodes. All underwent chronic long-term video/EEG monitoring, cortical mapping by 50 Hz electric cortical stimulation and recording of cortical somatosensory evoked potentials with chronically implanted subdural grid electrodes (3 mm in diameter and centre-to-centre distance of 1 cm) to map both epileptogenic and functional zones. After these clinical evaluations, cortical stimulation by single electric pulse (0.3 ms duration, 1 Hz) was carried out through pairs of subdural electrodes located at the primary sensorimotor area (MI-SI), pre-supplementary motor area (pre-SMA) and lateral negative motor area (lateral NMA), while surface EMG was recorded from the muscles of the contralateral hand. The results showed that (i) in all subjects, single pulse stimulation of MI-SI elicited a motor evoked potential (MEP) followed by a silent period (SP) in the contralateral distal hand muscles, the latter lasting 300 ms after the stimulus. The duration of SP was proportional to the size of the preceding MEP. In one subject, SP without any preceding MEP was elicited, and, in another subject, there was a short SP immediately before MEP in the contralateral thenar muscle. (ii) Following the stimulation of either pre-SMA or lateral NMA, no SP was observed. It is concluded that the inhibitory mechanism within the MI-SI, but probably not in the non-primary motor areas, either closely linked to or completely independent of excitation, most likely plays an important role in eliciting brief negative motor phenomena such as cortical negative myoclonus or SP.

Adult↗
PubMed2000

Abnormal premovement gating of somatosensory input in writer's cramp.

One characteristic of focal dystonia is the sensory trick, by which sensory input to a certain area of the body can reduce abnormal contractions in muscles nearby. This suggests that adjusting the link between sensory input and movement allows motor commands to be issued more effectively from the brain. To explore this sensorimotor link, we studied the attenuation (gating) of somatosensory evoked potentials (SEPs) before and during hand movements in patients with writer's cramp. For premovement gating, 10 patients and 11 age-matched normal subjects were given a warning sound followed 1s later by an electric stimulus to the right median nerve at the wrist. The latter served both as a reaction signal to start a finger extension task and as the input to evoke SEPs over the scalp. Because reaction times always exceeded 70 ms, short-latency SEPs thus obtained were unaffected by the afferents activated by the movement. The amplitudes of frontal N30 components were significantly decreased over the frontal leads compared with SEPs elicited at rest (P: < 0.002) in the normal group, whereas significant gating was found not for N30 but for frontal P22 (P: = 0. 002) in the patient group. For midmovement gating studies, SEPs to the right median nerve stimulation were recorded in 16 patients and 12 age-matched normal subjects at rest, and during active and passive finger extension-flexion movements. In contrast to the premovement SEPs, the frontal N30 was equally gated during active and passive movements both in the patient (P: < or = 0.002) and the normal group (P: < or = 0.003). These findings indicate that in writer's cramp the sensitivity of sensory input channels from the hand is wrongly set by the central command to move. Perhaps the sensory trick, by supplying additional input not usually present during unobstructed movement, is a manoeuvre to correct this imbalance. Dystonia may result not only from abnormalities in the central motor command but also from disturbed central processing of sensory input.

Adult↗
PubMed2000

Nonlinear Markov process amplitude EEG model for nonlinear coupling interaction of spontaneous EEG.

To develop an appropriate model for representing spontaneous electroencephalography (EEG) is an important and necessary work in the field of neuroscience. The Markov process amplitude (MPA) EEG model has been proposed in our previous work for representing the features of the EEG in terms of a few parameters. However, being a linear model, the linear MPA EEG model cannot perfectly describe the spontaneous EEG that displays nonlinear phenomena. In this paper, the nonlinear Markov process amplitude (nonlinear MPA) EEG model that includes nonlinear components is introduced. The consistent consideration of the nonlinear features of the EEG investigated by N. Wiener and P. L. Nunez can be seen from the nonlinear MPA EEG model. The similarity in the time domain and the goodness of fitting in the frequency domain with respect to the ongoing EEG are shown. As a result, the EEG power spectrum can be decomposed into the spontaneous components and the nonlinearly coupled components by use of the nonlinear MPA EEG model, which is useful for a better understanding the mechanism of the EEG generation.

Biomedical Engineering↗
PubMed2000

Use of cavernous sinus EEG in the detection of seizure onset and spread in mesial temporal lobe epilepsy.

PURPOSE: The study goal was to evaluate the clinical usefulness of intravenous EEG recording by placing wire electrodes in the cavernous sinus (CS) and the superior petrosal sinus (SPS) in patients with intractable temporal lobe epilepsy (TLE), with special emphasis on the ictal recording. METHODS: We placed Seeker Lite-10 guide wire as electrodes in the bilateral CS, SPS, or both to simultaneously record both ictal and interictal EEGs with the scalp EEG in five patients with TLE. In addition, in one patient, we averaged interictal scalp and intravascular EEG time-locked to the epileptiform discharge recorded from the CS/SPS-EEG to further delineate the relationship of the spikes between scalp and intravenous recording. RESULTS: In four of five patients, clinically useful recording was obtained to determine ictal focus. We recorded habitual seizures in three patients, and the detailed characteristics of ictal epileptiform discharges were shown. The averaged waveform of interictal epileptiform discharges clarified the spike distribution in the scalp EEGs, which was otherwise undetectable in the single trace. All of the patients completed the intravenous EEG monitoring without any neurological or psychological problems. CONCLUSIONS: The CS/SPS-EEG is a relatively noninvasive method that is useful for the detection of ictal focus and its spreading pattern and thus for the selection of surgical candidate among patients with intractable TLE. Although the number of seizures detected during the short monitoring period may be limited, due to the advantages of its safety and simplicity, it is worth trying for potential surgical candidates before more invasive examinations are applied. A further study with a larger number of patients is needed to estimate its practical risk.

Adult↗
PubMed2000

Carotid brainstem reflex myoclonus after hypoxic brain damage.

A patient comatose after acute anoxia developed bilaterally synchronous, periodic myoclonic jerks most prominently in the bilateral upper limbs. Although the myoclonus seemed to occur spontaneously, electrophysiological studies showed that the myoclonic jerks correlated in timing and size with arterial pulses, and was suppressed by massage over the carotid sinus. It is proposed that the present myoclonus is a variant of brainstem reflex myoclonus in which arterial pulses served as intrinsic trigger stimuli via the carotid sinus and the medullary reticular formation.

Aged↗
PubMed2000

Inaudible high-frequency sounds affect brain activity: hypersonic effect.

Although it is generally accepted that humans cannot perceive sounds in the frequency range above 20 kHz, the question of whether the existence of such "inaudible" high-frequency components may affect the acoustic perception of audible sounds remains unanswered. In this study, we used noninvasive physiological measurements of brain responses to provide evidence that sounds containing high-frequency components (HFCs) above the audible range significantly affect the brain activity of listeners. We used the gamelan music of Bali, which is extremely rich in HFCs with a nonstationary structure, as a natural sound source, dividing it into two components: an audible low-frequency component (LFC) below 22 kHz and an HFC above 22 kHz. Brain electrical activity and regional cerebral blood flow (rCBF) were measured as markers of neuronal activity while subjects were exposed to sounds with various combinations of LFCs and HFCs. None of the subjects recognized the HFC as sound when it was presented alone. Nevertheless, the power spectra of the alpha frequency range of the spontaneous electroencephalogram (alpha-EEG) recorded from the occipital region increased with statistical significance when the subjects were exposed to sound containing both an HFC and an LFC, compared with an otherwise identical sound from which the HFC was removed (i.e., LFC alone). In contrast, compared with the baseline, no enhancement of alpha-EEG was evident when either an HFC or an LFC was presented separately. Positron emission tomography measurements revealed that, when an HFC and an LFC were presented together, the rCBF in the brain stem and the left thalamus increased significantly compared with a sound lacking the HFC above 22 kHz but that was otherwise identical. Simultaneous EEG measurements showed that the power of occipital alpha-EEGs correlated significantly with the rCBF in the left thalamus. Psychological evaluation indicated that the subjects felt the sound containing an HFC to be more pleasant than the same sound lacking an HFC. These results suggest the existence of a previously unrecognized response to complex sound containing particular types of high frequencies above the audible range. We term this phenomenon the "hypersonic effect."

Acoustic Stimulation↗
PubMed2000

Vascular cell components of the medullary arteries in Binswanger's disease brains: a morphometric and immunoelectron microscopic study.

BACKGROUND AND PURPOSE: It has been hypothesized that fibrohyalinosis of the medullary arteries may cause white matter lesions in Binswanger's disease (BD). However, previous reports have been inconsistent on the pathological alterations of the cellular components, which may vary in terms of vessel sizes. We therefore quantitatively examined vasculopathy in the medullary arteries of a defined caliber in BD brains with a quantitative technique. METHODS: A total of 20 brains were examined: 10 from patients with BD and 10 from age-matched nonneurological control patients. The alterations in the vascular cell components were examined with quantitative immunohistochemistry and immunoelectron microscopy for collagen and smooth muscle actin. RESULTS: The nonneurological control patients showed no white matter lesions. In contrast, the patients with BD invariably had marked white matter lesions, as well as fibrohyalinosis of the medullary arteries. The ratio of the area immunolabeled for collagen type I and type IV to the cross-sectional area was 2-fold higher in the BD patients than in the control patients, regardless of the vessel caliber (P<0.005). Although the ratio for smooth muscle actin in the BD brains was increased in arteries of <100 microm (P<0.0001), there was no corresponding increase in the arteries of >100 microm. However, in the ultrastructure of these vessels, the cell bodies immunolabeled for smooth muscle actin were hypertrophic and segregated from each other by proliferated fibrils. The basal lamina appeared multilayered, and the endothelial cells were swollen. Collagen type I and type IV immunoreactive fibrils also proliferated in the pericapillary space of the BD brains. CONCLUSIONS: The proliferation of collagen fibrils in the media and adventitia of the blood vessels in BD brains was not specific to small arteries and arterioles but also occurred in the pericapillary spaces. Pericapillary sclerosis, smooth muscle cell proliferation in the terminal arterioles, and their morphological transformation in the proximal arteries may alter the shear rates and thus cause profound microcirculatory disturbances in BD brains.

Actins↗
PubMed2000

Automatic detection of open and closed eye states in the electroencephalographic (EEG) record for background EEG interpretation by the trigger method.

Automatic detection of open and closed eye states in electroencephalographic (EEG) records was investigated in this study as a part of procedures for the precise interpretation of the background EEG to achieve a comprehensive automatic EEG interpretation system. The features of eye open and closure were extracted from the EEG using a Markov process amplitude (MPA) EEG model, which could efficiently express the features of the EEG using a small number of parameters. A new technique, named the trigger method, was also developed to overcome the difficulty resulting from large differences in the EEG features among different subjects, because an accurate detection could not be obtained by using the conventional threshold method. The proposed method gave satisfactory results which conformed with those of visual inspection by a qualified EEGer and could be clinically used as a preprocessing method for the automatic interpretation of the awake background EEG.

Adult↗
PubMed2000

Cortical potentials associated with voluntary mandibular movements.

Movement-related cortical potentials (MRCPs) are negative potentials over the scalp, which gradually increase prior to voluntary movements, and might be applied to elucidate the cortical efferent function of the mandibular movements. We compared the MRCPs accompanying various mandibular movements to study the motor control mechanism underlying these movements. Electroencephalograms (EEGs) were recorded from 11 electrodes placed over the scalp (F3, Fz, F4, T3, C3, Cz, C4, T4, P3, Pz, and P4), according to the International 10-20 System, and electromyograms (EMGs) were obtained from surface electrodes over the masseter muscle and the anterior belly of the digastric muscle. Ten healthy subjects were requested to make brisk and self-paced mandibular movements in 4 different directions (mouth-opening and -closing, and left and right lateral movements). We obtained MRCPs by averaging the EEG, using the visually determined EMG onset as a trigger signal. In all the movements, a slowly increasing, bilaterally widespread negativity starting 1.5 to 2.0 sec before the EMG onset (Bereitschaftspotential, or BP proper) was observed, with the maximum over the vertex region. The negative slope (NS') occurred about 300 to 700 msec before the EMG onset. The cortical maps of BP/NS' (BP and NS' combined), immediately prior to the mouth-opening and closing, showed a symmetrical distribution, whereas that for the lateral movements showed a tendency of predominance over the hemisphere ipsilateral to the direction of the movement. BP/NS' amplitudes at the onset of movement differed significantly or tended to do so between open, close, and lateral movements, suggesting that MRCP recordings may thus provide a means to explore the role of the cerebral cortex in the control of mandibular movements.

Adult↗
PubMed2000

Avoidance of solidification of sesame oil at low temperature by self-interesterification with immobilized lipase.

To reduce the freezing point of sesame oil, the lipase-catalyzed interesterification of sesame oil in a solvent free system was studied. The lipase was immobilized on Celite and refined sesame oil was used as the only substrate for the reaction. After interesterification, the oil did not solidify at 0 degrees C even after 24 h, and even longer storage at 2-4 degrees C did not result in solidification. The change of physical behavior was investigated with a differential scanning calorimeter and X-ray diffraction, and reduction in the thermodynamic and crystallographic stability of the interesterified oil was demonstrated. The change in triacylglycerol species composition after the reaction was analyzed, showing that content of trisaturated acylglycerol was decreased.

Calorimetry, Differential Scanning↗
PubMed1999

Pre-movement gating of short-latency somatosensory evoked potentials.

Somatosensory evoked potentials (SEPs) are reduced in amplitude during movement (gating). The mechanism involves central gating of afferent input and competition from other afferents activated by the movement. We distinguished these two by giving 11 normal subjects a warning sound followed 1 s later by an electric stimulus to the right median nerve at the wrist. The latter served both as a cue to start a finger movement and as stimulation to evoke SEPs. Gating effects were widespread in frontal (N30) and central (N60) areas, but were also seen, albeit to a lesser extent, in the recordings at P3 (P30). Since finger movement began after the stimulus, such gating must have been purely central in origin, presumably reflecting motor preparation.

Adult↗
PubMed1999

The effect of sequential lesioning in the basal forebrain on cerebral cortical glucose metabolism in rats. An animal positron emission tomography study.

We studied the effect of the cortical projection from the basal forebrain on the cerebral cortical metabolism using positron emission tomography (PET) with [(18)F] fluorodeoxyglucose. Unilateral damage of the nucleus basalis magnocellularis (NBM) did not cause a permanent reduction of cortical metabolism: recovery was observed 4 weeks after the operation. Destruction of the contralateral side after recovery from unilateral damage produced persistent bilateral suppression of glucose metabolism, with partial recovery. We speculate that recovery from the unilateral NBM lesions is partly ascribable to the cholinergic projection from the contralateral NBM, and partly due to non-cholinergic systems, and conclude that bilateral damage might be responsible for persistent cortical glucose metabolism suppression.

Animals↗
PubMed1999

Cerebral glucose metabolism in unilateral entorhinal cortex-lesioned rats: an animal PET study.

To evaluate the effect of entorhinal cortical lesion on cerebral cortical function, we studied cerebral glucose utilization (CMRGlc) using a high resolution PET scanner after quinolinic acid lesion of the unilateral entorhinal cortex in rats. [18F]Fluorodeoxyglucose PET was performed at 4 days and 4 weeks after surgery, and CMRGlc in the bilateral frontal, parietal and temporal regions were analyzed. At 4 days, the entorhinal lesion induced a 12-15% decrease in CMRGlc of frontal, parietal and temporal regions ipsilateral to the lesion. The hypometabolism continued at 4 weeks in the temporal region. These findings suggest that entorhinal lesion induces cerebral cortical hypometabolism, which implies a pathogenetic role of entorhinal area on the cortical hypometabolism in Alzheimer's disease.

Analysis of Variance↗
PubMed1999

Somesthetic function of supplementary motor area during voluntary movements.

To clarify the somesthetic functions of the supplementary motor area (SMA), we recorded the cortical potentials following the median nerve electric stimulation directly from the SMA and investigated the modulation caused by voluntary movements in two patients with intractable SMA seizures. The evoked potentials over the SMA consisted of positive (61.5ms) and negative (100.0 ms) peaks, which were enlarged by voluntary movements of the stimulated hand. The present finding is in strong contrast with the attenuation (gating) of the response at the primary sensorimotor area (SM1) and suggests that the voluntary movements differently modulate the somatosensory functions of SMA and SM1.

Adult↗
PubMed1999

Activities of the primary and supplementary motor areas increase in preparation and execution of voluntary muscle relaxation: an event-related fMRI study.

Brain activity associated with voluntary muscle relaxation was examined by applying event-related functional magnetic resonance imaging (fMRI) technique, which enables us to observe change of fMRI signals associated with a single motor trial. The subject voluntarily relaxed or contracted the right upper limb muscles. Each motor mode had two conditions; one required joint movement, and the other did not. Five axial images covering the primary motor area (M1) and supplementary motor area (SMA) were obtained once every second, using an echoplanar 1.5 tesla MRI scanner. One session consisted of 60 dynamic scans (i.e., 60 sec). The subject performed a single motor trial (i.e., relaxation or contraction) during one session in his own time. Ten sessions were done for each task. During fMRI scanning, electromyogram (EMG) was monitored from the right forearm muscles to identify the motor onset. We calculated the correlation between the obtained fMRI signal and the expected hemodynamic response. The muscle relaxation showed transient signal increase time-locked to the EMG offset in the M1 contralateral to the movement and bilateral SMAs, where activation was observed also in the muscle contraction. Activated volume in both the rostral and caudal parts of SMA was significantly larger for the muscle relaxation than for the muscle contraction (p < 0.05). The results suggest that voluntary muscle relaxation occurs as a consequence of excitation of corticospinal projection neurons or intracortical inhibitory interneurons, or both, in the M1 and SMA, and both pre-SMA and SMA proper play an important role in motor inhibition.

Adult↗
PubMed1999

Cortical visuomotor integration during eye pursuit and eye-finger pursuit.

To elucidate cortical mechanisms of visuomotor integration, we recorded whole-scalp neuromagnetic signals from six normal volunteers while they were viewing a black dot moving linearly at the speed of 4 degrees /sec within a virtual rectangle. The dot changed its direction randomly once every 0.3-2 sec. The subject either (1) fixated a cross in the center of the screen (eye fixation task), (2) followed the moving dot with the eyes (eye pursuit task), or (3) followed the dot with both the eyes and the right index finger (eye-finger pursuit task). Prominent magnetic signals, triggered by the changes of the direction of the dot, were seen in all conditions, but they were clearly enhanced by the tasks and were strongest during the eye-finger pursuit task and over the anterior inferior parietal lobule (aIPL). Source modeling indicated activation of aIPL [Brodmann's area (BA) 40], the posterosuperior parietal lobule (SPL; BA 7), the dorsolateral frontal cortex (DLF; BA 6), and the occipital cortex (BA 18/19). The activation first peaked in the occipital areas, then in the aIPL and DLF, and some 50 msec later in the SPL. Our results suggest that all these areas are involved in visuomotor transformation, with aIPL playing a crucial role in this process.

Adult↗
PubMed1999

Sleep-disordered breathing at an early stage of amyotrophic lateral sclerosis.

Eighteen amyotrophic lateral sclerosis (ALS) patients having neither respiratory complaints nor subjective symptoms of sleep disturbance were studied by using an ambulatory multi-parameter monitoring system during sleep. They were divided into two groups: 11 patients with predominantly bulbar form and seven with non-bulbar form. After performing daytime pulmonary function tests, the presence of sleep-disordered breathing (SDB) was evaluated by using a portable device. ALS patients did not show significant SDB as a whole, and the respiratory disturbance index (RDI) was not significantly different between the bulbar group and the non-bulbar group. However, three patients of the bulbar group showed significant SDB, and the patterns of apnea/hypopnea suggested that both bulbar weakness and minimal diaphragmatic weakness might cause SDB in ALS patients at an early clinical stage. Multi-parameter respiratory monitoring during sleep should be included in the routine evaluation of ALS patients at an early clinical stage, especially those with predominantly bulbar involvement, in order to predict early respiratory failure.

Aged↗