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H Shibasaki

Publications and source records attributed to H Shibasaki.

At least 163 records · Page 9Linked to original sources
PubMed1997

The cortical generators of the contingent negative variation in humans: a study with subdural electrodes.

Contingent negative variations (CNVs) and Bereitschaftspotentials (BPs) were recorded from subdural electrodes implanted in 14 patients with intractable epilepsy. For recording CNVs, a Go/NoGo S2 choice reaction-time paradigm was employed. Two seconds after presentation of a low tone burst (S1), either a medium (S2m) or a high tone burst (S2h) was delivered at random. Patients were instructed to make middle finger extensions after S2m but not after S2h. For recording BPs, patients repeated self-paced middle finger extensions. BPs were recorded from the primary motor area (MI), the primary sensory area (SI) and the supplementary sensorimotor area (SSMA). CNVs showed a patchy distribution in the prefrontal area and SSMA for the early component and in the prefrontal area, MI, SI, temporal area, occipital area and SSMA for the late component. These results suggest that the CNV recorded from the scalp is the summation of multiple cortical potentials which have different origins and different functions. The cortical distribution of the late CNVs was different from that of BPs. Late CNVs are not equivalent to BPs and are not related to motor preparation alone. After S2, 3 kinds of potentials, probably related to decision making, somatosensory feedback and motor execution under specific conditions, respectively, were observed.

Adolescent↗
PubMed1997

Dissociation between contingent negative variation (CNV) and Bereitschaftspotential (BP) in patients with parkinsonism.

In order to clarify the generator mechanism of the late component of contingent negative variation (CNV), we compared the late CNV with Bereitschaftspotential (BP) in patients with parkinsonism (Parkinson's disease and progressive supranuclear palsy). In patients with mild symptoms (Hoehn Yahr grade I and II) both the late CNV and BP were clearly seen. In patients with severe symptoms (Hoehn Yahr grade III, IV and V) the BP was normally seen, but the late CNV was significantly smaller or absent (P < 0.001 at Cz) and it was also significantly smaller than that obtained from age-matched normals. In one patient (H-Y grade II) who had normal BP, the late CNV was diminished selectively at the midline area. Since it was reported that the late CNV arises from at least the supplementary motor area (SMA), selective diminution of the late CNV at the midline could be explained by the decreased activity of the SMA in parkinsonism. It was also previously reported that the BP was absent but the late CNV was normally present in a patient with cerebellar efferent lesion (Ikeda et al., 1994). Taken together with the experimental results indicating that movement-related neurons in the putamen behave contingent on external stimuli, it is suggested that subcortical generating mechanism is different for the late CNV and BP although both commonly share at least some cortical generators, and that the basal ganglia are most likely responsible for the generation of the late CNV and the cerebellar efferent system for the generation of the BP.

Adult↗
PubMed1997

Cortical mechanism underlying externally cued gait initiation studied by contingent negative variation.

In order to clarify the cortical mechanism underlying gait initiation, we examined the scalp distribution of the contingent negative variation (CNV) preceding externally cued gait initiation in a simple reaction-time paradigm in 10 healthy right-handed men, and compared the results with the CNV preceding simple foot dorsiflexion. A pair of auditory stimuli was given with an interstimulus (S1-S2) interval of 2 s and gait consisting of at least 3 steps was initiated with the right footstep as fast as possible in response to S2. Brisk dorsiflexion of the right foot was employed as a control task. It was found that the late CNV in the gait initiation task started about 1 s before S2, and was largest at Cz (-9.3 +/- 3.1 microV) without clear asymmetry over the scalp. However, it was ill defined in the parietal area. In the foot dorsiflexion task, the late CNV was maximal at Cz (-7.1 +/- 2.9 microV), and clearly seen also over the parietal area. The late CNV at Cz was significantly (P < 0.01) larger in the gait initiation than in the simple foot dorsiflexion. The amplitude of the late CNV preceding the foot dorsiflexion task was not significantly different between the sitting and the standing posture. In view of the results of previous invasive studies in both humans and animals which showed some frontal areas, including the supplementary motor area (SMA) and the primary motor cortex, as the generators of the late CNV, it is suggested that the cerebral cortex is active in initiation of externally triggered gait in a different way from the simple foot movement, and that bilateral SMAs may play a more important role in gait initiation than in simple foot movement.

Adolescent↗
PubMed1997

Subclinical REM sleep behavior disorder in a patient with corticobasal degeneration.

Various neurodegenerative diseases have been reported to be associated with rapid eye movement (REM) sleep behavior disorder (RBD). This is the first report of a patient with corticobasal degeneration (CBD) associated with subclinical RBD. A 72-year-old woman was admitted complaining of fine tremor of the right hand and weakness of the right lower extremity. She was diagnosed as having CBD on the basis of clinical features and neuroimaging studies. Her family noticed snoring and increase in sleep talk, but they did not regard them as pathological. All-night polysomnography (PSG) revealed REM sleep without atonia (RWA) during which 14 episodes of talking and singing were observed. They ranged from the utterance of one word to that of comprehensible words of a song for about 3 minutes accompanied by various nonpurposeful movements of the mouth, hands, and limbs. These episodes were not associated with any sleep-disturbed breathing. Future PSG studies on CBD patients together with postmortem analysis of brain stem structures that are crucial for generating REM sleep-related atonia are warranted for further understanding of the pathophysiological mechanism of RBD.

Aged↗
PubMed1997

Event-related potentials associated with judgment: comparison of S1- and S2-choice conditions in a contingent negative variation (CNV) paradigm.

To elucidate the functional role of association cortex in judgment and decision-making about external stimuli, the scalp topography of contingent negative variation (CNV) recorded in 9 normal volunteers was compared in two settings; dichotomous S1- and S2-choice paradigms using right wrist extension or flexion movement upon S2 as the choice reaction task with an S1-S2 interstimulus interval of 2 s. Two main findings were obtained. First, early CNV in the S1-choice paradigm consisted of a frontal to frontopolar midline negative potential, most likely representing judgment more than orienting response, and a left-sided parietal positive potential, at least partially representing P3b, whereas in the S2-choice paradigm it consisted only of a smaller frontal negative potential shift, most likely representing merely an orienting response. This suggests that the prefrontal and left parietal association cortexes might be active in the judgment and decision-making process. Second, after S2, two positive peaks (334 and 545 ms after S2) were observed at the midline central to left parietal areas only in the S2-choice paradigm. In the S1-choice paradigm, one large negative peak (275 ms after S2) was observed. We postulate that the first peak of the S2-choice paradigm is related to decision making or judgment and that the second peak is related to the following cognitive process. We conclude that at least the prefrontal and parietal association cortexes generate transient potentials accompanying judgment, and possibly decision making.

Adult↗
PubMed1997

Frontopolar ictal epileptiform discharges on scalp electroencephalogram in temporal lobe epilepsy.

We report 3 patients with medically intractable complex partial seizures (CPS) arising from the temporal lobe judged by surgical outcome, in whom scalp electroencephalogram (EEG) showed ictal epileptiform discharges at the frontopolar region. In all patients, results of cranial magnetic resonance imaging (MRI), positron emission tomography (PET), and ictal single photon emission computed tomography (SPECT) were consistent with those of temporal lobe epilepsy (TLE). The epileptogenic area was defined in the temporal lobe by chronic subdural recording in 2 patients. After surgical treatment (amygdalohippocampectomy, anterior temporal lobectomy, and temporal lesionectomy, respectively), all 3 patients became seizure-free and the interictal frontopolar epileptiform discharges on scalp EEG disappeared. Patients with TLE may show ictal scalp EEG with frontopolar onset. This is most likely explained by direction of dipolar orientation of epileptiform discharges in 1 of our patients; rapid spread of ictal activity to the frontopolar area can also be considered in the 2.

Adult↗
PubMed1997

Scalp-recorded, ictal focal DC shift in a patient with tonic seizure.

PURPOSE: We recorded focal ictal DC shifts from scalp electrodes in a 9-year-old boy with intractable, clinically generalized tonic seizures. The patient had a high intensity signal abnormality of the left temporal cortex with thickening of the gyri on T2-weighted MRI. METHODS: Scalp digital EEGs were recorded using electrodes made of silver/silver chloride. The low frequency filter (LFF) was set at 0.016 Hz. Recorded seizures were subsequently analyzed with LFF settings of 1.0, 0.016 and 0.03 Hz. RESULTS: All recorded seizures initially showed diffuse, low voltage, high frequency activity (electrodecremental pattern) followed 10-20 s later by quasirhythmic activity over the left frontotemporal region. In two seizures, LFF of 0.016-0.03 Hz revealed a slow negative shift over the left frontotemporal area simultaneously with onset of the bilateral electrodecremental pattern. However, in the other seizures, this initial slow negative shift was obscured by artifacts. Subsequent electrocorticography (ECoG) delineated frequent epileptiform discharges in the left temporal as well as frontal cortex. CONCLUSIONS: Scalp-recorded ictal DC shifts may help identify focal epileptogenic brain area in patients with clinically generalized seizures although the technique is vulnerable to artifact.

Child↗
PubMed1997

Subdural recording of Bereitschaftspotential is useful for functional mapping of the epileptogenic motor area: a case report.

A 26-year-old man with intractable focal motor seizure beginning with tonic contraction of the left orbicularis oculi muscle had prolonged EEG monitoring with subdural grid electrodes placed over the right perirolandic cortex. Electrical stimulation of the cortex with implanted subdural electrodes showed a relatively low threshold for afterdischarges (ADs) but could not disclose the motor area for the left upper face where or near where the epileptogenic area was expected to be present. Bereitschaftspotential recorded from the subdural electrodes in association with self-paced voluntary blink (eyelid closing) disclosed the motor area specifically related to voluntary movements of the left upper face, which was most likely buried in the sulcus. This observation suggests that recording of Bereitschaftspotential from subdural electrodes is useful for mapping the motor cortex, especially in patients with focal motor seizure with low threshold for ADs to electric stimuli.

Adult↗
PubMed1997

"Cavernous sinus EEG": a new method for the preoperative evaluation of temporal lobe epilepsy.

PURPOSE: In presurgical evaluation of temporal lobe epilepsy (TLE), invasive methods are necessary if results of various noninvasive methods are not sufficiently convergent enough to identify the epileptogenic area accurately. To detect the epileptiform discharges originating specifically from the mesial temporal lobe, we applied the cavernous sinus catheterization technique. METHODS: We placed Seeker Lite-10 guide wire electrodes into bilateral cavernous sinus through the internal jugular veins to record EEG (cavernous sinus EEG) in 6 patients with intractable TLE. Scalp EEG was simultaneously recorded in all 6 and electrocorticogram (ECoG) was also recorded in 4. RESULTS: The cavernous sinus EEG demonstrated clear epileptiform discharges, sometimes even when they were absent on the simultaneously recorded scalp EEG. The epileptiform discharges recorded from the cavernous sinus electrodes were specifically associated with those in the mesial temporal region on ECoG. Ictal EEG pattern originating from mesial temporal lobe was also clearly documented on the cavernous sinus EEG. CONCLUSIONS: This new, semi-invasive method of identifying epileptogenic areas can detect the epileptiform discharges specifically arising from the mesial temporal lobe; it is as useful as or complements the invasive techniques such as foramen ovale or depth recording.

Adolescent↗
PubMed1997

Human second somatosensory area: subdural and magnetoencephalographic recording of somatosensory evoked responses.

OBJECTIVE: To investigate somesthetic functions of the perisylvian cortex. METHODS: Somatosensory evoked magnetic fields (SEFs) and somatosensory evoked potentials (SEPs) of the perisylvian cortex were recorded directly from subdural electrodes in a patient with a left frontal brain tumour. RESULTS: The most prominent SEP components after electrical stimulation of the right and left hands and the right foot were double peaked negativity recorded just above the sylvian fissure (latency 80 to 150 ms), respectively (N1a and N1b). Generator sources for the magnetoencephalographic counterparts of those peaks (N1a(m) and N1b(m)) were both localised at the upper bank of the sylvian fissure, and those of N1a(m) were more anteromedially located than those of N1b(m). CONCLUSIONS: These findings suggest the existence of at least two separate somatosensory areas within the human perisylvian cortex.

Adult↗
PubMed1997

REM sleep motor dysfunction in multiple system atrophy: with special emphasis on sleep talk as its early clinical manifestation.

Various neurodegenerative diseases involving brainstem structures as one of the main pathological lesions are reported to be associated with REM sleep behaviour disorder. Full blown REM sleep behaviour disorder can be diagnosed clinically, but REM sleep motor dysfunction, a pathophysiological basis of REM sleep behaviour disorder, is difficult to detect without all night polysomnography. Twenty one consecutive patients with multiple system atrophy with no complaints of nocturnal abnormal behaviours were clinically evaluated to determine the presence of sleep related symptoms. All night polysomnography with video monitoring was performed to investigate REM sleep characteristics and patients' behaviours. In 85.7% (18 of 21) of the patients' sleep talk started or increased around or after the clinical onset of the primary diseases. REM sleep without atonia occupied more than 15% (16.2%-100%) of the REM sleep time in all but one patient. In 90.5% (19 of 21) of patients, motor events such as sleep talk and various combinations of craniofacial, orofacial, or limb movements occurred at various frequencies mostly during REM sleep without atonia. In patients with multiple system atrophy, REM sleep motor dysfunction is a common polysomnographic finding which is otherwise overlooked, and sleep talk may be its early clinical manifestation.

Aged↗
PubMed1997

Assessment of benzodiazepine receptors using iodine-123-labeled iomazenil single-photon emission computed tomography in patients with ischemic cerebrovascular disease. A comparison with PET study.

BACKGROUND AND PURPOSE: [123I]Iomazenil (IMZ) is a tracer used for single-photon emission computed tomography (SPECT) that has the characteristics of selectively binding to central benzodiazepine receptors (BZR) in the neuron membrane. To determine whether IMZ SPECT provides new information on assessing neuronal damage after ischemic insult to the brain, we compared IMZ SPECT images with the cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), and cerebral metabolic rate of glucose (CMRGlc) studied by position emission tomography in the chronic stage of ischemic stroke. METHODS: Five patients (male; mean age, 63.2 +/- 6.0 years) with ischemic cerebrovascular disease and 6 age- and sex-matched normal control subjects were studied. IMZ images obtained 180 minutes after injection were analyzed for BZR binding, and these images were compared with the CBF, CMRO2, and CMRGlc obtained by position emission tomography in the same perfusion areas both visually and quantitatively. RESULTS: In the visual analysis of data obtained from 4 patients with subcortical infarction, decreased IMZ accumulation was observed locally in the overlying normal-appearing cortices of the affected hemisphere, where extensive hypoperfusion and hypometabolism were seen on the images of CBF, CMRO2, and CMRGlc. The regional relative IMZ uptake (regional to cerebellar ratio) for all 5 patients was significantly correlated with the corresponding regional CMRO2 values (r = .45, P < .05). However, no significant correlation was found of the IMZ uptake with either the regional CBF or the regional CMRGlc. CONCLUSIONS: The use of IMZ SPECT provides new information on the neuronal alteration induced by chronic ischemic cerebrovascular disease.

Aged↗
PubMed1997

Tinnitus remission by lidocaine demonstrated by auditory-evoked magnetoencephalogram. A preliminary report.

An auditory-evoked magnetic field was recorded before and during tinnitus remission induced by an intravenous lidocaine injection. One and 4 kHz probe tones were presented monaurally in four tinnitus patients, and the responses were recorded using a 122-channel magnetometer. Three normal volunteers were also examined as controls. In tinnitus patients, the N100 m peak became sharper, while there was no marked change except for slight reduction in amplitude in normal subjects. Tinnitus remission by lidocaine may be related to attenuation of a masking-like effect of tinnitus on the sound-evoked responses.

Aged↗
PubMed1997

[Use of jerk-locked back averaging for detecting the epileptiform discharge in a patient with supplementary motor seizure].

A 23-year-old, right handed women has suffered from supplementary motor seizures manifesting tonic followed by clonic contractions of the left foot, occasionally spreading to the left hand and trunk, since the age of 7 years. The mean frequency of seizures on admission was about 10 times per day. A brain MRI showed an abnormal intensity area about 3 cm in diameter in the right mesial frontal lobe involving the superior frontal and cingulate gyri. Six habitual seizures were recorded during long-term monitoring with digital EEG segments time-locked to the clonic contractions of the left foot, a negative spike was detected about 50 ms before the EMG onset at the midline fronto-central area slightly lateralized to the left. In the focal motor seizure arising from the mesial frontal lobe like in the present case, jerk-locked back averaging helps detecting the epileptiform activity which is otherwise undetectable.

Adult↗
PubMed1997

[A case of cortical reflex myoclonus manifesting tremor].

A 58-year-old woman developed slowly progressive tremulous myoclonus provoked mainly by action and posture. She had neither seizure nor dementia. No one in her family had similar symptoms. The presence of giant somatosensory evoked potentials (SEP) with enhanced long loop reflex and premovement cortical spikes demonstrated by the jerk-locked averaging method suggest that the involuntary movement is cortical reflex myoclonus. Magnetoencephalogram revealed that the generator sources of giant SEPs were the post-central somatosensory cortex and probably also the pre-central motor cortex. Symptoms improved after treatment with zonisamide, clonazepam and valpolate. This kind of involuntary movement might be called cortical myoclonic tremor.

Anticonvulsants↗
PubMed1996

Neural control of micturition in man examined with single photon emission computed tomography using 99mTc-HMPAO.

THE neural mechanisms of micturition in man were studied using single photon emission computed tomography (SPECT). The areas activated during micturition, relative to the resting state, were the upper pons, the left sensorimotor cortex, the right frontal cortex and the bilateral supplementary motor areas. Some of these regions have been established by clinical and experimental studies as the neural control centre for voiding. We confirmed the neural micturition centre in healthy men using SPECT for the first time.

Adult↗