Biomedical subjects

S Tobimatsu

Publications and source records attributed to S Tobimatsu.

At least 19 recordsLinked to original sources

PubMed1996

Western versus Asian types of multiple sclerosis: immunogenetically and clinically distinct disorders.

The polymorphism of HLA-DRB1, -DRB3, and -DRB5 genes as well as magnetic resonance images of the brain and spinal cord were studied in 57 Japanese patients with multiple sclerosis (MS). Twenty-three patients clinically displayed selective involvement of the optic nerve and spinal cord and were classified as having Asian-type MS. The other 34 patients had disseminated central nervous system involvement and were classified as having Western-type MS. Patients with Asian-type MS had fewer brain lesions shown by magnetic resonance imaging, but more gadolinium-enhanced spinal cord lesions than did patients with Western-type MS (47% vs 17%). Furthermore, the DR2-associated DRB1*1501 allele and DRB5*0101 allele were associated with Western-type MS (41.2%), but not with either Asian-type MS (0%) or healthy control subjects (14.2%). Heterogeneity in the immunogenetic background and in the magnetic resonance imaging features between the two subtypes of MS thus suggests the presence of two etiologically distinct diseases in Asians.

Alleles↗

PubMed1996

Human VEPs to isoluminant chromatic and achromatic sinusoidal gratings: separation of parvocellular components.

To extract the responses specific to the parvocellular system (color vision and form perception) in humans, visual evoked potentials (VEPs) in response to the onset of isoluminant chromatic (red-green) and achromatic (black-white) sinusoidal gratings were recorded in 15 young adults. Chromatic stimulation evoked a characteristic negative wave (N1) with peak latencies around 120 msec. The amplitude resembled an inverse U-shaped function against the spatial frequency with a peak at 2 c/deg. In contrast, VEPs to achromatic gratings showed different spatial frequency characteristics with a peak at 5.3 c/deg. With variations in the luminous intensity ratio between the red and green gratings, N1 was seen to respond maximally to isoluminant stimulation. These results indicate that the combined use of isoluminant chromatic and achromatic patterns could stimulate the parvocellular system selectively in humans.

Adult↗

PubMed1996

The effect of binocular stimulation on each component of transient and steady-state VEPs.

We recorded the monocular and binocular VEPs to the alternation of sinusoidal gratings in order to evaluate the binocular interaction in each component of transient and steady-state VEPs in 13 normal subjects. Three spatial frequencies (1.3, 2.6 and 5.3 c/deg) with a 90% contrast were used as visual stimuli. The latencies and amplitudes of N70 and P100 of the transient VEPs were measured. The steady-state VEPs were Fourier analyzed, and both the phase and amplitude of the second (2F) and fourth (4F) harmonic responses were obtained. Binocular interaction was influenced by spatial frequency such that a binocular summation or even an inhibition occurred. For the transient VEPs, a binocular summation was more pronounced in the amplitude of N70 than in that of P100 at all spatial frequencies. There were no significant effects of binocular stimulation on latencies of N70 or P100. However, the latencies of N70 and P100 showed different spatial frequency characteristics. For the steady-state VEPs, the amplitude of 2F revealed a binocular summation that was more pronounced at 5.3 c/deg, whereas the 4F amplitude showed binocular inhibition at 2.6 and 5.3 c/deg. The 2F phase showed binocular inhibition at all spatial frequencies, whereas no such inhibition was observed in the 4F phase. These results suggest that individual components of transient and steady-state VEPs are physiologically distinct and may therefore be generated from different neuronal populations in striate cortex.

Adult↗

PubMed1996

Normal variability of the amplitude and phase of steady-state VEPs.

The present study quantifies the amplitude and phase variability of steady-state VEPs (S-VEPs) and compares this variability between subjects and between individual runs. The S-VEPs were recorded repeatedly in 14 normal subjects with varying spatial and temporal frequencies of sinusoidal gratings; 6 spatial frequencies (range 0.5-8.0 c/deg) with 3 temporal frequencies (4, 6 and 8 Hz) were used. A total of 75 responses were averaged and analyzed by the Fourier method. Four recordings were obtained in each spatio-temporal combination. In general, the phase data showed small inter- and intrasubject variability. As anticipated, the amplitude data showed a large degree of intersubject variability, although the intrasubject variability was very small. In addition, in some stimulus conditions the inter- and intrasubject variability increased, which thus suggested the existence of an optimal spatio-temporal combination. Therefore, these stimulus parameters should be taken into consideration when S-VEPs are applied in clinical practice.

Adult↗

PubMed1995

Functional mapping of the sensorimotor cortex: combined use of magnetoencephalography, functional MRI, and motor evoked potentials.

Combined use of magnetoencephalography (MEG), functional magnetic resonance imaging (f-MRI), and motor evoked potentials (MEPs) was carried out on one patient in an attempt to localise precisely a structural lesion to the central sulcus. A small cyst in the right frontoparietal region was thought to be the cause of generalised seizures in an otherwise asymptomatic woman. First the primary sensory cortex was identified with magnetic source imaging (MSI) of somatosensory evoked magnetic fields using MEG and MRI. Second, the motor area of the hand was identified using f-MRI during hand-squeezing. Then transcranial magnetic stimulation localised the hand motor area on the scalp, which was mapped onto the MRI. There was a good agreement between MSI, f-MRI and MEP as to the location of the sensorimotor cortex and its relationship to the lesion. Multimodality mapping techniques may thus prove useful in the precise localisation of cortical lesions, and in the preoperative determination of the best treatment for peri-rolandic lesions.

Adult↗

PubMed1995

Parvocellular and magnocellular contributions to visual evoked potentials in humans: stimulation with chromatic and achromatic gratings and apparent motion.

Psychophysical evidence suggests that two major parallel pathways, the parvocellular (P) and the magnocellular (M) pathways, exist in humans. We herein report that responses specific to the P and M systems can be recorded in human visual evoked potentials (VEPs) by using the appropriate stimuli. The onset of isoluminant chromatic (red-green) and high contrast achromatic sinusoidal gratings were used for stimulating the P-system. A chromatic stimulation evoked a characteristic negative wave (N1) with peak latencies around 120 msec. The amplitude showed an inverse U-shaped function as a function of spatial frequency with a peak at 2 c/deg. In contrast, VEPs to achromatic (black-white) gratings showed different spatial frequency characteristics with a peak at 5.3 c/deg. By varying the luminous intensity ratio between the red and green gratings, N1 was found to reach a maximum during isoluminant stimulation. An apparent motion display was used for stimulating the M-system. The speed of alternation (i.e., the interstimulus interval (ISI)) was varied to record both the transient and steady-state VEPs. Transient VEPs showed triphasic waves with the major positive peak (P1) at around 120 ms. Steady-state VEPs were quasi-sinusoidal waveforms, depending on the ISI, and were quite stable across all subjects. There was a also high correlation between the motion threshold and the VEP amplitude. The above observations indicate that characteristic potentials may distinguish between these two parallel visual systems in humans. Thus, the combined use of isoluminant color and high contrast achromatic gratings and an apparent motion display is considered to be useful for evaluating both systems electrophysiologically.

Adolescent↗

PubMed1995

The interaction of the somatosensory evoked potentials to simultaneous finger stimuli in the human central nervous system. A study using direct recordings.

In order to investigate the interaction of sensory electrophysiologic fields arising from the adjacent second (II) and third (III) fingers and the distant second and fifth (V) fingers, direct recordings of somatosensory evoked potentials (SEPs) were performed from the sensory and motor cortices, the sensory thalamic nucleus (nucleus ventralis caudalis, VC) and the cuneate nucleus in humans during neurosurgical operations. Electrical stimulation was given to the II, III or V fingers individually, and also to pairs of either the II and III fingers or the II and V fingers simultaneously. The interaction ratio (IR) was devised as the ratio of amplitude attenuation caused by the simultaneous stimulation to two fingers compared with the amplitude of the arithmetically summed SEPs to the individual stimulation of two fingers. The IRs were calculated on N20 and P25 from the sensory cortex, P22 from the motor cortex, P17thal from the VC, and N16cune and P35cune from the cuneate nucleus. With both stimulations to the II and III fingers and the II and V fingers, P25 showed the greatest IR, followed by P22, then by P17thal, with N16cune exhibited the smallest IR. N20 and P35cune showed similar IRs and significantly greater IRs with II and III finger stimulation compared with II and V finger stimulation. These results thus indicate that the interaction of somatosensory impulses occurs in several structures along the sensory pathway in CNS, including the cuneate nucleus, the sensory thalamic nucleus, as well as sensory and motor cortices, with the greatest IRs in the cerebral cortices and the weakest ones in the brain-stem.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

Aging and pattern visual evoked potentials.

Visual abilities decline during senescence. Age-related declines cannot be attributed entirely to changes in optical factors (senile miosis and opacification of the ocular media) and must therefore be caused by changes in the visual pathways. Because pattern visual evoked potentials (VEPs) provide information regarding the sensory function and integrity of the visual system, recent research on age-related changes in VEPs is reviewed. The results of this review show that stimulus parameters of VEPs (luminance, contrast, spatial and temporal frequencies) modify the age-related changes in VEPs. The visual system consists of multiple, parallel channels which process different information. Therefore, it is hypothesized that aging may affect the specific functional subdivisions in the visual pathways differentially.

Adolescent↗

PubMed1995

[Segmental muscular atrophy of unilateral upper limb associated with cervical disc herniation in a juvenile male].

A 25-year-old man first noticed atrophy of right upper arm at the age of 15. This symptom progressed for the following 3 years and then became stable. As he noted difficulty in elevating his right arm above the shoulder level, at the age of 25 he was admitted to our hospital. On neurological examination, he had right scapula alata, moderate atrophy and weakness of right triceps muscle. Right triceps reflex was absent. Other neurological examinations were normal. Needle electromyography revealed neurogenic patterns in the muscles of the C5-T1 segments. Cervical MRI and CT myelography revealed mild cervical disc protrusion toward the right side at the C5/6 level and atrophy of the middle and lower cervical cord on the right side, but nothing suggestive of the fexion myelopathy. The clinical manifestations of the patient resembled those of Hirayama disease, except for the distribution of the involved muscles. Since the most severely involved level of the cervical cord (C7 segment) corresponded to the level of the protruded cervical disc, it was suggested that the cervical disc herniation played an important role in the development of the myelopathy in this patient.

Adult↗

PubMed1994

Periodic synchronous discharges and visual evoked potentials in Creutzfeldt-Jakob disease: PSD-triggered flash VEPs.

We have developed the technique of flash visual evoked potentials (VEPs) triggered by periodic synchronous discharges (PSDs) to investigate the interaction between PSDs and VEPs in 3 patients with Creutzfeldt-Jakob disease (CJD). This technique enables us to explore the cerebral pathophysiology underlying CJD. Unexpectedly, we found that PSDs and VEPs did not interact even when VEPs were evoked in close temporal proximity to PSDs. Thus, it appears that PSDs are generated by a different neuronal mechanism from that involved in VEP generation.

Adult↗

PubMed1994

Temporal frequency deficit in patients with senile dementia of the Alzheimer type: a visual evoked potential study.

To study the temporal aspect of visual processing of senile dementia of the Alzheimer type (SDAT), we recorded the steady-state visual evoked potentials (VEPs) to LED goggle stimulation at five different temporal frequencies in 14 patients with SDAT and 14 control subjects. For comparison, we also studied 14 patients with vascular dementia (VD). All subjects were women, and their ages were closely matched. Temporal frequencies were 5, 10, 15, 20, and 30 Hz. The steady-state VEPs were Fourier analyzed, and both the amplitude and phase of the first and second harmonic responses were obtained. There was a significant difference in the amplitude across the three groups for stimulation at 15, 20, and 30 Hz, but no difference at a stimulation of 5 and 10 Hz. Multiple comparison tests revealed that patients with SDAT had a significantly smaller amplitude than normal controls. Patients with VD had lower amplitudes than normal subjects, but this was not statistically significant. In the phase data, there were also no statistically significant differences across the three groups for any of the temporal frequencies. These results indicate that a temporal frequency deficit exists in SDAT. This phenomenon may be explained by the pathology that affects the early stage of visual signal processing.

Aged↗

PubMed1994

Vitamin B12 metabolism and massive-dose methyl vitamin B12 therapy in Japanese patients with multiple sclerosis.

Serum vitamin B12 levels and unsaturated vitamin B12 binding capacities were measured in 24 patients with multiple sclerosis (MS), 73 patients with other neurological disorders and 21 healthy subjects. There was no decrease in the vitamin B12 levels, however, a significant decrease in the unsaturated vitamin B12 binding capacities was observed in patients with MS when compared with other groups. A massive dose of methyl vitamin B12 (60 mg every day for 6 months) was administered to 6 patients with chronic progressive MS, a disease which usually had a morbid prognosis and widespread demyelination in the central nervous system. Although the motor disability did not improve clinically, the abnormalities in both the visual and brainstem auditory evoked potentials improved more frequently during the therapy than in the pre-treatment period. We therefore consider that a massive dose methyl vitamin B12 therapy may be useful as an adjunct to immunosuppressive treatment for chronic progressive MS.

Adult↗

PubMed1994

[Visual information processing in humans].

Recent advances in parallel information processing of primates and humans have been reviewed. First, I review what is known about physiology and anatomy of the primate visual pathways. Several lines of evidence suggest that the primate visual system consists of the parvocellular (P) and the magnocellular (M) pathways. M-system originates from the A retinal ganglion cells that project to the visual cortex (V1) via the magnocellular layers of the lateral geniculate nucleus (LGN). This system plays an important role for motion and stereopsis. P-system derives from the B retinal ganglion cells that project to V1 via the parvocellular layers of the LGN. This system shows selectivity for color vision and form perception. Second, I focus on the information processing of the human visual pathways. Psychophysical evidence suggests that there are also P and M systems in humans. However, there have been few electrophysiological studies which intend to separate the responses specific to P and M systems in human visual evoked potentials (VEPs). Based on the physiological distinctions between P and M systems, the use of isoluminant color patterns and apparent motion display allows us to evaluate P and M systems, respectively.

Animals↗

PubMed1993

Primary progressive versus relapsing remitting multiple sclerosis in Japanese patients: a combined clinical, magnetic resonance imaging and multimodality evoked potential study.

Thirty-five Japanese patients with relapsing remitting multiple sclerosis (RRMS) and 11 Japanese patients with primary progressive MS (PPMS) were compared by a combined clinical, magnetic resonance imaging (MRI) and multimodality evoked potential (MEP) study. Patients with PPMS showed a more common occurrence of gait disturbance as the initial symptoms as well as a more common occurrence of cerebellar symptomatology than did those with RRMS, while spinal cord symptomatology was frequently observed in both conditions. On brain MRI, patients with PPMS had 3 times more lesions than did those with RRMS (P < 0.001, chi 2-test). The percentage of infratentorial lesions was also significantly higher in PPMS than in RRMS on MRI. Moreover, we found a significantly higher frequency of abnormal records in visual, brainstem auditory and somatosensory evoked potentials in PPMS than in RRMS. Interestingly, clinically unexpected abnormalities were significantly more common in PPMS than in RRMS throughout all modalities of MEPs. Thus, in Eastern MS, there exists a distinction between PPMS and RRMS in the MRI and MEP findings as well as in the clinical findings. Our result therefore suggest that there may be two distinct subtypes in MS.

Adult↗

PubMed1993

Effect of spatial frequency on transient and steady-state VEPs: stimulation with checkerboard, square-wave grating and sinusoidal grating patterns.

We recorded VEPs to the alteration of checkerboard, square-wave grating and sinusoidal grating patterns to evaluate the contribution of the fundamental spatial frequency and higher harmonic components in 12 normal subjects. Their fundamental spatial frequencies were equated and ranged from 0.5 to 8.0 c/deg. Both the transient VEP (T-VEP) and steady-state VEP (S-VEP) were obtained. The latency and amplitude of P100 of T-VEPs were measured. S-VEPs were Fourier analyzed, and phase and amplitude of the second harmonic response were measured. The mean P100 latency and the mean phase had a U-shaped function with a peak at a fundamental spatial frequency of 2.0 c/deg irrespective of the stimulus patterns, while the mean P100 amplitude and the mean amplitude of S-VEPs did not show such spatial selectivity. At low and medium spatial frequencies, differences in P100 latency, phase and amplitude between pattern types were more pronounced. However, this difference became insignificant at high spatial frequencies. These results indicate that VEP responses are predominantly determined by the fundamental spatial frequency, and that the contribution of higher harmonics to VEP responses is not negligible. Our results are consistent with the concept that the human visual system may use spatial frequency-domain information.

Adult↗

PubMed1993

[The variation of human contrast sensitivity with age and optic nerve disease].

Contrast sensitivity function (CSF) was measured in 85 normal subjects and in 23 patients with optic neuropathy, using a personal computer and video monitor system. CSF in normal controls showed an inverted U-shaped function against spatial frequency with a peak at about 4-6 cycles/degree. At higher spatial frequencies, contrast sensitivity decreased with increasing age. CSF in patients was compared with Snellen acuity, visual field examination, critical flicker fusion frequency (CFF) and pattern VEP (P-VEP). CSF and P-VEP were more sensitive than the others in detecting visual dysfunction in optic nerve disease. These results suggest that ranges of normal values should be established for each of several age groups, and that CSF is useful for evaluating visual dysfunction.

Adult↗

PubMed1992

[Adverse effect of antiepileptic drugs on the visual recognition--a contrast sensitivity function study].

Contrast sensitivity function (CSF) was measured in 16 patients (14-60 yr.) with epilepsy to investigate adverse effect of antiepileptic drugs on the central nervous system. Eight patients were treated with phenytoin, while 8 were given polytherapy (phenytoin in combination with phenobarbital, carbamazepine or valproic acid). Thirty-one normal controls (19-59 yr.) were also subjected to this study. Vertical sinusoidal gratings with various spatial frequencies (0.5-20.0 c/deg) were presented on a video monitor. Contrast sensitivity (reciprocal of threshold contrast) was determined at each spatial frequency. CSF of normal subjects showed an inverted U-shaped function against the spatial frequencies with a peak at 6 c/deg (medium size pattern). There was no significant difference in CSF values between normal controls and patients with epilepsy. However, 3 patients with polytherapy showed the significant reduction of contrast threshold. Since these patients did not complain of visual disturbance with normal visual acuity, CSF abnormality was considered as having subclinical visual dysfunction. These results suggest that CSF is useful for evaluating the adverse effect of antiepileptic drugs on the visual recognition, and that polytherapy is responsible for CSF abnormality. Therefore, monotherapy should be scheduled from the onset of therapy.

Adult↗

PubMed1992

The neurophysiologic significance of frontal negativity in pattern-reversal visual-evoked potentials.

To demonstrate that the frontal negative potential (N100) does exist in response to pattern-reversal visual stimulation and its independence of the dipole source from the major occipital positive potential (P100), modifications of P100 and N100 with changes in the check size, contrast, and luminance of the stimulus pattern were studied in healthy subjects. Eight different check sizes (10-90 min of arc), eight different contrast levels (10-85%), and six different luminance levels (11-180 cd/m2) were used. Changing the stimulus conditions modified the latencies and amplitudes of P100 and N100 in different ways. P100 latency had a band pass spatial tuning function against check size; N100 latency did not. P100 was sensitive to changes in contrast and luminance; N100 was less dependent on these parameters. These findings suggest the existence of different physiologic properties for N100. Consequently, frontal negativity is considered to be independent of P100.

Adult↗