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Biomedical subjects

H Shibasaki

Publications and source records attributed to H Shibasaki.

At least 181 records · Page 10Linked to original sources
PubMed1996

Functional anatomy on perception of position and motion in depth.

To investigate the neural substrates for the perception of motion and of position in depth, we examined the changes in regional cerebral blood flow during positional and motion stereopsis in humans by positron emission tomography. During positional stereopsis, the right striate and peristriate cortices (areas V1/V2 and V3) and the inferior parietal lobule were significantly activated. During motion stereopsis, the right striate and peristriate cortices (V1/V2) and the ventrolateral occipital cortex (V5) were significantly activated. These results suggest that brain regions active during stereopsis may be dependent, despite their considerable overlap, on the properties of stereopsis, i.e. positional or motion stereopsis.

Adolescent↗
PubMed1996

Abnormal sensorimotor integration in writer's cramp: study of contingent negative variation.

To investigate the pathophysiology of idiopathic focal dystonia, we recorded contingent negative variation (CNV) as a physiological index of sensorimotor integration in 14 right-handed patients with writer's cramp and compared it with normative data. CNV was recorded in the S2 choice reaction time paradigm: Two kinds of auditory S2 (Go or No-Go) were given 2 s after the auditory S1, and the subject reacted only to the Go signal by extending the wrist. In normal subjects, the late CNV amplitude had no difference at Cz between left- and right-hand tasks and was symmetric without significant amplitude laterality irrespective of the side of hand movement. In patients with writer's cramp, the late CNV amplitude at Cz was relatively larger for the left-hand task than the right-hand task (p < 0.03), and a significant amplitude laterality of the late CNV (larger on the right) was present especially at the central area for the right-hand task (p < 0.03). Since the late CNV is known to be generated, at least in part, from primary and supplementary motor cortices, the significant laterality of the late CNV seen with the right-hand task in patients with writer's cramp might represent functional abnormality of motor cortices possibly as the result of basal ganglia function.

Adult↗
PubMed1996

Clinical trial of piracetam in patients with myoclonus: nationwide multiinstitution study in Japan. The Myoclonus/Piracetam Study Group.

Sixty patients with disabling myoclonus excluding mainly spinal myoclonus were treated by piracetam as an open-labeled study, and myoclonus score, neurological symptoms, functional disability, and intensity of myoclonus were scored before and after treatment, including a blinded video inspection. Electrophysiological correlation also was investigated before and after treatment. Piracetam was effective in myoclonus, especially that of cortical origin, in both monotherapy and polytherapy. Piracetam also had positive benefits on gait ataxia and convulsions but not on dysarthria, and feeding and hand writing improved much more significantly. Psychologically significant improvement was seen in decreased motivation, sleep disturbance, attention deficit, and depression, all of which might be possibly secondary benefits associated with improvement of myoclonus. There was no positive correlation between clinical and electrophysiological improvement. Tolerance was good, and side effects were transient. However, hematological abnormalities observed in at least two patients in the present study should be kept in mind when relatively large doses of piracetam are administered, especially in combination with other antimyoclonic drugs.

Administration, Oral↗
PubMed1996

Focal cortical blood flow activation is regulated by intrinsic cortical cholinergic neurons.

We evaluated the cholinergic mechanism underlying focal cortical vascular response to neuronal activation, using positron emission tomography for use on animals to measure cerebral blood flow and glucose metabolism activation upon vibrotactile stimulation in cats. Bromopyruvate, which blocks acetylcholine synthesis through inhibition of the production of acetyl CoA, was injected into the cerebral cortex and basal forebrain as well as the sphenopalatine ganglion, all of which have been confirmed to supply cholinergic terminals to the cerebral cortex. Although glucose metabolism was preserved, indicating that the neuronal activities were enhanced, cerebral blood flow increase during cortical neuronal activation was abolished by bromopyruvate injection into only the cerebral cortex and not other cholinergic systems. We conclude that the cholinergic intrinsic neurons control the focal cerebral blood flow increase in response to neuronal activation.

Analysis of Variance↗
PubMed1996

Time-varying activation of different cytoarchitectonic areas of the human SI cortex after tibial nerve stimulation.

We followed cortical activation in eight healthy adults after electric stimulation of the left tibial nerve at the ankle. The recordings were made noninvasively with a whole-scalp neuromagnetometer. The first cortical activation peaked in different subjects at 37-45 ms in the foot area of the right (contralateral) primary somato-sensory (SI) cortex, with mean source current orientation perpendicular to the longitudinal fissure. The current orientation changed within the next 5 ms counterclockwise in all subjects, with a mean rotation of 64 degrees. A two-dipole time-varying model, with two dipoles differing by 28-119 degrees in orientation but less than 1 cm in location in the right SI cortex, explained the signal pattern satisfactorily during the first 100 ms. We suggest that the observed field patterns reflect sequential activation of different cytoarchitectonic areas in the foot SI cortex and imply considerable differences in the structural organization between the foot and the hand SI cortices. The initial activation is considered to take place in area 3b facing the interhemispheric fissure, and the later source, due to the systematic rotations of the field patterns, is assumed to reflect activation of area 5 in the anterior wall of the marginal ramus of the cingulate sulcus.

Adult↗
PubMed1996

Somatosensory evoked potentials following proprioceptive stimulation of finger in man.

Brisk passive flexion of the proximal interphalangeal joint of the middle finger, produced by using a newly devised instrument, elicited evoked potentials on the scalp. The present study carefully excluded the possible contribution of sensory modalities other than proprioception. The initial part of cortical response was a positive deflexion at the contralateral central area (P1 at 34.6 ms after the stimulus). This was followed by a midfrontal negative wave (N1 at 44.8 ms) and a clear positivity at the contralateral centroparietal area (P2 at 48.0 ms). The evoked responses persisted in spite of the abolition of cutaneous and joint afferents of the finger caused by ischemic anesthesia, but they were lost by ischemic anesthesia of the forearm. Thus, the cortical evoked responses obtained in this study most probably reflect muscle afferent inputs. The scalp distribution of P1 suggested that its cortical generator source was different from that of the N20-P20 components of evoked potentials to electrical median nerve stimulation. Brodmann areas 2 and 3a of human brain, which are known to receive deep receptor inputs, are the most plausible generator sites for the early components of the proprioception-related evoked responses. The amplitude of P2 was related to the velocity but not to the magnitude of movement. In conclusion, the present study established a method for recording the evoked responses to the brisk passive movement of the finger joint, which mainly reflect the dynamic aspects of proprioception mediated through muscle afferent.

Adult↗
PubMed1996

Simplified quantification of regional cerebral blood flow with 99mTc-ECD SPECT and continuous arterial blood sampling.

The goal of this study was to develop a simple method for quantification of regional cerebral blood flow (rCBF) with 99mTc-ethyl cysteinate dimer (ECD) SPECT. Following an intravenous constant infusion of ECD for one minute, serial dynamic SPECT imaging was performed for 40 minutes in 6 healthy male volunteers with intermittent arterial blood sampling. PET scan with 15O-water was performed on the same day before the SPECT study for measurement of rCBF. Arterial blood data demonstrated rapid conversion of ECD to the hydrophilic metabolites, and most of the arterial input to the brain was completed within 5 minutes after the injection. Brain activity reached a peak value soon after the cessation of infusion, and was stable thereafter with very little washout. Net extraction of ECD in the brain calculated by arterial input of ECD and rCBF demonstrated a rapid decrease within a few minutes, reaching 42.7% at 5 minutes. The simulation study suggested that the arterial blood activity obtained by continuous drawing for 5 minutes and a single SPECT scan would provide a reasonable estimate of rCBF under the assumption of constant net extraction in the brain.

Adult↗
PubMed1996

Pain-related and cognitive components of somatosensory evoked potentials following CO2 laser stimulation in man.

We recorded cortical potentials evoked by painful CO2 laser stimulation (pain SEP) employing an oddball paradigm in an effort to demonstrate event-related potentials (ERP) associated with pain. In 12 healthy subjects, frequent (standard) pain stimuli (probability 0.8) were delivered to one side of the dorsum of the left hand while rare (target) pain stimuli (probability 0.2) were delivered to the other side of the same hand. Subjects were instructed to perform either a mental count or button press in response to the target stimuli. Two early components (N2 and P2) of the pain SEP demonstrated a Cz maximal distribution, and showed no difference in latency, amplitude or scalp topography between the oddball conditions or between response tasks. In addition, another positive component (P3) following the P2 was recorded maximally at Pz only in response to the target stimuli with a peak latency of 593 msec for the count task and 560 msec for the button press task. Its scalp topography was the same as that for electric and auditory P3. The longer latency of pain P3 can be explained not only by its slower impulse conduction but also by the effects of task difficulty in the oddball paradigm employing the pain stimulus compared with electric and auditory stimulus paradigms. It is concluded that the P3 for the pain modality is mainly related to a cognitive process and corresponds to the P3 of electric and auditory evoked responses, whereas both N2 and P2 are mainly pain-related components.

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

Cortical potentials preceding voluntary elbow movement in recovered hemiparesis.

Scalp-recorded movement-related cortical potentials (MRCPs) preceding voluntary elbow flexion were studied in two hemiparetic patients 8 months after a stroke. Both cases had unilateral lenticular and internal capsular vascular lesion sparing the cortex. The motor recovery stage of their paretic arm remained in flexion or extension "synergistic" movements of shoulder, elbow, wrist and fingers. The NS' (negative slope) amplitude preceding voluntary unilateral elbow flexion of the intact arm showed a distinct preponderance over the contralateral precentral area, whereas NS' amplitude preceding flexion of the paretic arm was symmetrically maximal at bilateral precentral areas. It is postulated that the unilateral synergistic elbow flexion of the paretic arm is associated with an activation of bilateral brachial areas of the sensorimotor cortex (SI-MIs), whereas the isolated elbow flexion of the intact arm is associated with an activation of mainly the contralateral SI-MI.

Adult↗
PubMed1996

Subdural potentials at orbitofrontal and mesial prefrontal areas accompanying anticipation and decision making in humans: a comparison with Bereitschaftspotential.

Field potentials associated with the execution of a warned choice Go/No-Go reaction task were recorded from prefrontal supplementary (SMA) and primary motor cortex (MI) by using subdural electrodes in 5 epileptic patients during presurgical evaluation. The choice was between a Go and a No-Go imperative stimulus (S2) in the S1-S2 paradigm. Orbitofrontal and mesial prefrontal areas generated a slow preceding potential before S2 (most likely late CNV), and bilateral mesial prefrontal areas generated a transient potential, most likely related to decision making, upon S2 in both Go and No-Go conditions. In self-paced, repetitive movement, the Bereitschaftspotential was seen only at SMA and MI, but not in the prefrontal area. The present result, therefore, suggests that in humans orbitofrontal and mesial frontal areas play an important role in preparation for cognition and in decision making, whereas SMA and MI do so in motor preparation.

Adult↗
PubMed1996

Movement-related slow cortical magnetic fields and changes of spontaneous MEG- and EEG-brain rhythms.

Cortical activity was recorded from 5 healthy adults with a 122-channel whole-head magnetometer while the subjects performed during unilateral finger movements at self-paced intervals exceeding 6 s. The readiness field (RF) started over the contralateral somatomotor area 0.3-1 s prior to the movement onset in subjects (Ss) 1, 2, and 4, and culminated in the motor field (MF) 30 ms after it (Ss 1-4). These signals were followed by movement evoked fields MEFI (Ss 1-5) and MEFII (Ss 1-4) at 100-150 ms and 200-250 ms after the movement onset, respectively. One subject showed clear RF over the ipsilateral hemisphere as well. The contralateral dominance of the RF contrasted the more symmetric distribution of the simultaneously recorded electric Bereitschaftspotential (BP). The RF onset never preceded the BP onset. We suggest that BP receives contribution from the early bilateral activation of the crown of the precentral gyrus, whereas RF reflects later activity of the fissural motor cortex. Spontaneous oscillations in the background activity (spontaneous activity) of approximately 10 Hz started to dampen 2-3 s prior to the movement onset in the somatomotor areas of both hemispheres with contralateral predominance (S1 and S3), and returned to a steady level 0.8-2 s after the movement onset in all subjects. Higher frequency bands in the same area displayed a prominent rebound about 1 s after the movement onset in 4 subjects. Execution of self-paced movements is evidently expressed differently in the slow movement-related fields and in the cortical spontaneous activity.

Adult↗
PubMed1996

Cerebral activation during performance of a card sorting test.

The Wisconsin Card Sorting Test (WCST) is used clinically for evaluating frontal lobe function, but there is some controversy as to its specificity for detecting frontal lobe damage. To investigate the cerebral regions essential to the performance of the Card Sorting Test, we measured the regional cerebral blood flow (rCBF) in 18 normal subjects by PET under the three conditions: (i) during the Modified Card Sorting Test (MCST); (ii) during a matching-to-sample (MTS) task, based on the MCST, but with selective attention to one of three stimulus categories (colour, number or shape) as a control to cancel the effects of maintenance of sets in the MCST; (iii) under resting conditions as overall control. When rCBF during the MCST was compared with that during each MTS task separately, significant activations were observed during the MCST in the left or bilateral dorsolateral prefrontal cortex (DLPFC), bilateral inferior parietal lobes, left superior occipital gyrus and left cerebellum. Compared with all the MTS tasks inclusively, significant increase in rCBF was detected during the MCST in the bilateral DLPFC, inferior parietal lobes, striate cortex, cerebellum and left occipital cortex. These results suggest the involvement of the DLPFC and other related areas such as the inferior parietal cortex in the execution of the MCST, and may help explain why a variety of brain lesions can result in impaired performance on the Card Sorting Test.

Adult↗
PubMed1996

Supplementary motor area seizure resembling sleep disorder.

Two patients presented with a complaint of frequent sudden arousals during sleep followed by tachypnea and palpitation associated with stiffness in the upper extremities in one case and by elevation of the left lower limb in the other. All night video-electroencephalogram (EEG) polysomnography (VPSG) confirmed the diagnosis of seizure arising from the supplementary motor area (SMA seizure) in both cases. Carbamazepine (CBZ) produced remarkable improvement both in clinical seizures and in their subjective sleep quality. Repeated polysomnography after treatment showed a clear improvement in sleep architecture with higher percentages of slow wave sleep. SMA seizure could disturb nocturnal sleep and is one of the important differential diagnoses for a patient complaining of frequent arousals associated with motor disturbance during sleep.

Adult↗
PubMed1996

Subdural recording of ictal DC shifts in neocortical seizures in humans.

PURPOSE: Invasive ictal EEG recording is often necessary to delineate epileptogenic areas in patients with intractable partial epilepsy, but even intracranial ictal recordings often reveal ill-defined onset zones in neocortical epilepsy. We studied the physiologic significance of ictal direct current (DC) potentials recorded intracranially in human epilepsy. METHODS: We made intracranial ictal EEG recordings in three patients with intractable partial seizures arising from frontal, lateral temporal, and parietal neocortical areas by using closely spaced subdural electrodes (platinum in two patients and stainless steel in one patient) with both standard (1.5 Hz) and open (0.016 Hz) low-frequency filter (LFF) settings. RESULTS: The initial ictal pattern was localized to two to nine subdural electrodes and characterized by very low voltage and high-frequency rhythmic activity ("electrodecremental pattern"). A slow-rising negative potential (DC potential) was seen in a slightly more restricted area (two to six electrodes) and occurred 1-10 s before the initial ictal EEG discharges in two patients. CONCLUSIONS: These results agree with those of previous studies of ictal DC shifts in animals and suggest that ictal DC shifts may be helpful in delineating the epileptogenic area more precisely in human epilepsy.

Adolescent↗
PubMed1996

Pain-related somatosensory evoked potentials can quantitatively evaluate hypalgesia in Wallenberg's syndrome.

In 6 patients with Wallenberg's syndrome who showed a dissociated loss of pain sense, we recorded pain-related somatosensory evoked potentials following CO2 laser stimulation of the hand dorsum (pain SEPs). Two components, N2 and P2, were recorded by stimulation of the unaffected hand, whereas on the affected side they were absent or decreased in proportion to the severity of hypalgesia which was evaluated by both needle test and CO2 laser stimulation. Latency of either component, if appeared, was longer in the affected hand stimulation than that in the unaffected one. In contrast, N20 of the conventional electrically-stimulated SEPs (electric SEPs) showed no difference between the two sides. It is concluded that, unlike other electrophysiological methods, pain SEPs following CO2 laser stimulation can quantitatively evaluate functional impairment of the spinothalamic tract in Wallenberg's syndrome.

Adult↗