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Biomedical subjects

Shozo Tobimatsu

Publications and source records attributed to Shozo Tobimatsu.

At least 19 recordsLinked to original sources
PubMed2006

EEG findings in early-stage corticobasal degeneration and progressive supranuclear palsy: a retrospective study and literature review.

OBJECTIVE: Although neuroimaging and electrophysiological tests are potentially useful to distinguish corticobasal degeneration (CBD) from progressive supranuclear palsy (PSP), little is known about the diagnostic value of electroencephalography (EEG) for their distinction. We assessed the value of EEG for differentiating CBD from PSP. METHODS: We reviewed conventional EEGs recorded at an early stage of disease in 10 CBD patients and 14 PSP patients. We focused on slowing of background activity (SBA), frontal intermittent rhythmic delta activity (FIRDA) and focal slow waves (FSWs). Statistical analysis was performed by Fisher's exact test. RESULTS: SBA was observed in 1 CBD patient and 2 PSP patients. FSWs were found in 8 CBD patients (80.0%), but only 2 PSP patients (14.3%) (p=0.002); they appeared contralateral to the dominantly-affected side in 6 of 8 CBD patients, and ipsilateral to the side with most atrophy on MRI in 7 of 8 CBD patients. FIRDA was observed in 2 CBD patients (20.0%) and 5 PSP patients (35.7%) (p=0.357). CONCLUSIONS: FSWs are characteristic of CBD, but FIRDA was not disease-specific. SIGNIFICANCE: FSWs on EEG, in addition to clinical criteria, yield useful supplementary information to distinguish between these diseases at early stages.

Adult↗
PubMed2006

Studies of human visual pathophysiology with visual evoked potentials.

Visual evoked potentials (VEPs) offer reproducible and quantitative data on the function of the visual pathways and the visual cortex. Pattern reversal VEPs to full-field stimulation are best suited to evaluate anterior visual pathways while hemi-field stimulation is most effective in the assessment of post-chiasmal function. However, visual information is processed simultaneously via multiple parallel channels and each channel constitutes a set of sequential processes. We outline the major parallel pathways of the visual system from the retina to the primary visual cortex and higher visual areas via lateral geniculate nucleus that receive visual input. There is no best method of stimulus selection, rather visual stimuli and VEPs' recording should be tailored to answer specific clinical and/or research questions. Newly developed techniques that can assess the functions of extrastriate as well as striate cortices are discussed. Finally, an algorithm of sequential steps to evaluate the various levels of visual processing is proposed and its clinical use revisited.

Brain Diseases↗
PubMed2006

Functional network of the basal ganglia and cerebellar motor loops in vivo: different activation patterns between self-initiated and externally triggered movements.

The basal ganglia and cerebellar loops are known to participate differently in self-initiated (SI) and externally triggered (ET) movements. However, no previous neuroimaging studies have illustrated functional organization of these loops in vivo. Here, we aimed to functionally visualize these loops during motor execution using functional magnetic resonance imaging (fMRI) with structural equation modeling (SEM). Twelve normal subjects (24-29 years old) were scanned while performing five different frequencies of sequential left finger movements using either SI or ET movements. Random effect analysis combined with a parametric approach revealed a significant positive linear dependence of cerebral activation upon movement rate in the right Put, GPi, VL, SMC and SMA during SI tasks. During ET tasks, significant positive linear relationships were found in the right SMC, VPL, left CB and DN, whereas tendency for linear relationships was seen in the right PMv. SEM further showed significant interactions within the right basal ganglia-thalamo-motor loop during SI tasks. In contrast, there were significant interactions within the entire right cerebral hemisphere-left cerebellar loop involving CB, DN, VPL, PMv and SMC during ET tasks. Therefore, our modeling approach enabled identification of different contributions of the motor loops of basal ganglia and cerebellum to SI and ET tasks during motor execution.

Adult↗
PubMed2005

Familiarity facilitates the corticocortical processing of face perception.

The visual evoked potentials elicited by mosaic pictures were used to elucidate the initial step of face perception. Three different mosaic levels (subthreshold, threshold, suprathreshold) for familiar and unfamiliar faces and objects were randomly presented for 250 ms. The latencies of occipital N1 and posterior-temporal N2 were shortened by decreasing the mosaic levels of faces but not for object. The N2 amplitude significantly increased at threshold and suprathreshold levels for familiar and unfamiliar faces. The latency difference between N1 and N2 at threshold level for a familiar face was significantly shortened compared with that for an unfamiliar face. Our findings suggest the initial step of face perception is already set in the primary visual cortex, and familiarity can facilitate the corticocortical processing of face information.

Adult↗
PubMed2005

Left hemisphere specialization for rapid temporal processing: a study with auditory 40 Hz steady-state responses.

OBJECTIVE: To investigate rapid temporal processing in the auditory cortex by using auditory 40 Hz steady-state responses (SSRs). METHODS: A 40 Hz tone-burst at 500 Hz spectral frequency was presented monaurally to record SSRs in 10 normal subjects. The recording electrodes were placed over C1, C2, C3, C4, C5, C6, T3, T4, Fz, Cz and Pz, referring to an electrode at the 7th cervical spinous process. For comparison, unstimulated SSRs were recorded. A total of 200 responses of 1s epoch were averaged and subjected to discrete fast Fourier transforms to yield the amplitude and phase of the 40 Hz component. The coherence (Coh) values of the 40 Hz component between homologous electrodes were also calculated. RESULTS: At the temporal electrodes contralateral to the stimulated ear, the amplitude was significantly larger and its phase was significantly smaller than those of the ipsilateral side. The interhemispheric Coh between T3 and T4 in response to right ear stimulation was significantly greater than those of left ear stimulation or the unstimulated condition. CONCLUSIONS: Our results suggest that 40 Hz auditory information is predominantly processed in the left auditory cortex, interacting with the right hemisphere. This finding is consistent with the fact that the left auditory cortex plays an important role in rapid temporal processing. SIGNIFICANCE: Auditory 40 Hz SSRs with Coh analysis are useful for investigating the left hemisphere specialization for rapid temporal processing.

Acoustic Stimulation↗
PubMed2005

Functional characterization of mismatch negativity to a visual stimulus.

OBJECTIVE: To record mismatch negativity (MMN) to a visual stimulus fulfilling similar criteria to those of auditory MMN (A-MMN). METHODS: Twelve normal adults were instructed to simultaneously listen to a story and to pay attention to a visual target. Three windmill patterns that differed in the number of vanes (standard, deviant, or target) were used as visual stimuli, and were randomly presented. To ensure endogeneity, standard and deviant stimuli were alternated. To vary differences between frequent (standard) and infrequent (deviant) stimuli, deviants were changed by modulating the number of vanes. To examine effects of physical features of the target stimulus on changes in detection, two target conditions were used. The deviant-related component (DRC) was obtained by subtracting event-related potentials (ERPs) to the deviant stimulus from those to the standard stimulus. RESULTS: Seven subjects completed all phases of the experiment. Behavioral performances indicated that subjects' attention was directed by auditory context and identification of the target stimulus. Visual DRC appeared 150-300 ms after stimulus onset, and consisted of an early (DRN1) and a late (DRN2) component. Magnitude of deviancy from standard stimulus significantly influenced latency of DRN2 but not its magnitude, while changes in target stimulus affected latencies of both DRN1 and DRN2. CONCLUSIONS: Our DRCs satisfied criteria for A-MMN. In contrast to A-MMN, only latency of the DRC was associated with visual sensory discrimination and attentional reorienting. SIGNIFICANCE: It is possible to record valid MMN to a visual stimulus, which allows the study of preattentive visual information processing.

Adult↗
PubMed2005

Cerebral concentrations of myo-inositol in rats with induced brain death.

In anaesthetized, mechanically ventilated rats with brain death induced by epidural balloon inflation, we assessed the levels of cerebral myo-inositol in three brain areas 4 h after brain death had been confirmed. The levels were measured using HPLC, along with the water content. Myo-inositol levels were significantly increased in the cerebellum (P<0.05) and decreased in the brainstem (P<0.001), compared to findings in controls. Such changes can serve as hallmarks of brain death.

Animals↗
PubMed2005

Ocular dominancy in conjugate eye movements at reading distance.

We recorded conjugate eye movements to elucidate whether ocular dominancy was present at reading distance in 21 normal volunteers with the right-handedness by using a video-oculographic (VOG) measurement. This included the velocity of smooth pursuits, and the latency and velocity of saccades. We defined the dominant eye for each subject by means of the near-far alignment test and 20 subjects showed the right dominant eyes. Although the ocular dominancy was not found in the velocity of smooth pursuit and vertical saccades, the velocity of horizontal saccades in the dominant eyes was faster than that in the non-dominant eyes. These results suggest that the dominant eye is functionally activated prior to non-dominant eye in horizontal saccades at reading distance, which thus indicates the functional dominancy of the dominant eye in conjugate eye movements.

Adult↗
PubMed2005

[A patient with focal dystonia induced by golf and presenting a decrease in activity of cerebral motor cortex on task].

We here report a 45-year-old man with left arm focal dystonia induced by golf. He was a swimming instructor. From 35 years of age, he swung a golf club for 4 hours everyday. At 37 years of age, he noted difficulties in moving left arm when swinging, and developed involuntary movement of left arm toward his back thereafter. His involuntary movement was exacerbated even in several years after stopping both golf and swimming. Neurologically, simultaneous contraction was observed in left triceps and biceps muscles and his left arm dropped when raising arm to front. A 'sensory trick' was also observed. Thus, he was diagnosed as having a rare focal dystonia, and its clinical characteristics and course were basically different from those of 'yips', a focal dystonia that is characterized by anxiety and distal dominant dystonia presenting only on golf. Magnetic resonance imaging (MRI), FDG-positron emission CT (FDG-PET), C11-Raclopride PET and 99mTc-single photon emission CT (SPECT) revealed no abnormality in cerebral cortex and basal ganglias. However, motor evoked potentials (MEPs) were not evoked bilaterally when magnetic stimulation was applied on primary motor cortex. On functional MRI (fMRI), 40 seconds raising left arm task-induced activation in the right primary motor, supplementary motor, and premotor areas was apparently decreased, while left motor areas, the normal side, were reasonably activated. Motor-associated areas are generally overactivated by task in focal dystonia patients whereas excitability in primary motor area is decreased in idiopathic generalized dystonia. Therefore, dystonia of the present case appears to be similar to focal dystonia clinically but may partly have a mechanism similar to idiopathic generalized dystonia as shown in the fMRI studies.

Arm↗
PubMed2004

Effect of immunotherapy in myelitis with atopic diathesis.

OBJECTIVE: A recent nationwide survey of myelitis with atopic diathesis in Japan disclosed that the disease frequently shows a chronic persistent course. A neuropathological study of the spinal cord also revealed chronic active inflammation. Since the effects of various immunotherapies have not been studied extensively in this condition, we evaluated the efficacies of various immunotherapies in patients with myelitis with atopic diathesis. PATIENTS AND METHODS: Forty-two treatments in 26 patients with myelitis with atopic diathesis were retrospectively analyzed. One of the following therapies was administered: (1) corticosteroids (CS) (pulse therapy followed by oral administration with gradual tapering); (2) intravenous immunoglobulin (IVIG) (400 mg/kg/day for 5 consecutive days); (3) plasma exchanges (PE); or (4) PE followed by IVIG or CS (PE+IVIG/CS). The therapeutic efficacies were evaluated by thorough neurological examination and laboratory tests including MRI, somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs). RESULTS: Objective neurological findings improved in 89% of the PE group and 90% of the PE+IVIG/CS group, compared with only 72% of the CS and 60% of the IVIG groups. Improvement determined by laboratory tests was seen in 57% of the PE and 57% of the PE+IVIG/CS groups, compared with only 15% of the CS and none of the IVIG groups. Thus, the improvement rate determined by laboratory tests was significantly greater for therapies including PE than for those without PE (p=0.0187). CONCLUSIONS: These data suggest that immunotherapy is effective in myelitis with atopic diathesis despite a chronic persistent course, and that PE is the most beneficial immunotherapy.

Adolescent↗
PubMed2004

Electrophysiological correlates of associative visual agnosia lesioned in the ventral pathway.

Visual agnosia has been well studied by anatomical, neuropsychological and neuroimaging studies. However, functional changes in the brain have been rarely assessed by electrophysiological methods. We carried out electrophysiological examinations on a 23-year-old man with associative visual agnosia, prosopagnosia and cerebral achromatopsia to evaluate the higher brain dysfunctions of visual recognition. Electrophysiological methods consisted of achromatic, chromatic and category-specific visual evoked potentials (CS-VEPs), and event-related potentials (ERPs) with color and motion discrimination tasks. Brain magnetic resonance imaging revealed large white matter lesions in the bilateral temporo-occipital lobes involving the lingual and fusiform gyri (V4) and inferior longitudinal fasciculi due to multiple sclerosis. Examinations including CS-VEPs demonstrated dysfunctions of face and object perception while sparing semantic word perception after primary visual cortex (V1) in the ventral pathway. ERPs showed abnormal color perception in the ventral pathway with normal motion perception in the dorsal pathway. These electrophysiological findings were consistent with lesions in the ventral pathway that were detected by clinical and neuroimaging findings. Therefore, CS-VEPs and ERPs with color and motion discrimination tasks are useful methods for assessing the functional changes of visual recognition such as visual agnosia.

Adult↗
PubMed2004

Interhemispheric functional synchronization at the first step of visual information processing in humans.

OBJECTIVE: We examined the interhemispheric functional synchronization of the visual cortex using coherence (Coh) analysis. METHODS: Achromatic or isoluminant chromatic sinusoidal grating stimuli were presented to each hemifield at a rate of 8 reversals/s to record steady-state visual-evoked potentials (S-VEPs) in 10 healthy subjects. Four recording electrodes were placed at O1, O2, P3 and P4, referred to an electrode at Cz. A total of 50 responses of 1 s epoch were averaged, and were subjected to discrete fast Fourier transforms to yield the amplitude and phase of the 8 Hz component. Ordinary and partial Coh values were also calculated. RESULTS: For both achromatic and chromatic stimuli, the 8 Hz amplitudes of O1 and O2 were significantly larger than those of P3 and P4 without any significant difference between O1 and O2. The phase lag between O1 and O2 was approximately 30 degrees (latency shift 10.4 ms). Partial Coh between O1 and O2 at 8 Hz was significantly greater than that of the unstimulated condition, and this was only observed at 8 Hz. CONCLUSIONS: These results suggest that interhemispheric synchronization in the occipital area occurs despite the nature of the visual stimuli. Therefore, the activation of interhemispheric connection is important for the early stage of the visual information processing. SIGNIFICANCE: Our results indicate that the first step of the visual information processing requires interhemispheric functional synchronization.

Adult↗
PubMed2004

Subclinical cranial nerve involvement in hereditary motor and sensory neuropathy: a combined conduction study with electrical and magnetic stimulation.

OBJECTIVE: To evaluate the electrophysiological findings of clinically unaffected cranial nerves (facial, accessory and hypoglossal nerves) in hereditary motor and sensory neuropathy (HMSN). METHODS: The conduction times of the facial, accessory, and hypoglossal nerves in 10 patients with HMSN type I (HMSN I), 2 patients with HMSN Type II (HMSN II), and 20 normal controls were determined. The extra- and intracranial segments of the cranial nerves were stimulated electrically and magnetically, respectively. The relationships between the conduction parameters of the cranial nerves and limb nerves were analyzed. RESULTS: In patients with HMSN I, the conduction times of the distal and proximal segments were significantly prolonged in all 3 cranial nerves. A positive correlation was found between the conduction parameters of the cranial nerves and the limb nerves. CONCLUSIONS: Electrophysiological involvement of the whole segment of the facial, accessory and hypoglossal nerves is common in patients with HMSN I without clinical signs of alterations. The degree of conduction slowing of the facial, accessory, and hypoglossal nerves paralleled that of limb nerves.

Accessory Nerve↗
PubMed2004

Changes of the cerebral mannitol concentrations in the course of brain death of a rodent model.

Determining the time of brain death is one of the critical issues in forensic examinations. Few authors have attempted to determine the time of brain death using pharmacokinetic approaches. We investigated cerebral concentrations of mannitol of which a single dose (1 g/kg) was administered in the course of brain death. The inflation of an epidural balloon was adopted as a rodent model of brain death. Brain death was determined using ordinary tests. Specimens were collected 4 h after brain death. Brain water content was higher in brain dead (BD) groups than those in control groups. Cerebral concentrations of mannitol in the BD group were significantly higher than those in the control group (P<0.01). In all areas of brain the concentration was the highest at the time when mannitol was administered during balloon inflation. Interhemispheric difference in the cerebrum was observed, followed by balloon inflation (P<0.05). Significant differences were observed in the average concentration of administered mannitol before and after brain death in the contralateral hemisphere (P<0.01) and in the brainstem (P<0.01). As the concentrations of mannitol in the brain are affected by cerebral trauma and brain death follows, mannitol can be used to determine the time of brain death at forensic examinations.

Animals↗
PubMed2004

Non-invasive evaluation of face and motion perception in humans.

The neural mechanisms for the perception of face and motion were studied using psychophysical threshold measurements, event-related potentials (ERPs), and functional magnetic resonance imaging (fMRI). A face-specific ERP component, N170, was recorded over the posterior temporal cortex. Removal of the high-spatial-frequency components of the face altered the perception of familiar faces significantly, and familiarity can facilitate the cortico-cortical processing of facial perceptions. Similarly, the high-spatial-frequency components of the face seemed to be crucial for the recognition of facial expressions. Aging and visuospatial impairments affected motion perception significantly. Two distinct components of motion ERPs, N170 and P200, were recorded over the parietal region. The former was related to horizontal motion perception while the latter reflected the perception of radial optic flow motion. The results of fMRI showed that horizontal movements of objects and radial optic flow motion were perceived differently in the V5/MT and superior parietal lobe. We conclude that an integrated approach can provide useful information on spatial and temporal processing of face and motion non-invasively.

Cognition Disorders↗
PubMed2004

[Development of visual function: a neurophysiological point of view].

Recent findings on the development of visual function in children are summarized. First, visual evoked potentials (VEPs) in normal school children, following two types of visual stimuli (pattern reversal and light emitting diode stimulation) by transient and steady-state stimulation, are presented. Reproducible VEPs with the 4 stimulation conditions can be obtained. Transient and steady-state methods provide complementary results. Second, mechanisms for photosensitive epilepsy (PSE) are discussed. We recorded flicker VEPs to different color combinations and quantified the effects of changes in color and luminance combinations. Two amplitude peaks (9 and 18 Hz) were observed for all kinds of isoluminant color combination stimuli against temporal frequency. In addition, this characteristic was modulated by luminance. Normal children showed much higher sensitivity to contrast changes and color combination compared with normal young adults, which may be responsible for PSE in childhood. Third, cognitive function for facial expression of normal children and adults is mentioned. For Chernoff's faces showing anger and sadness produced by computer, children showed higher scores compared with adults, suggesting higher sensitivity for facial expression. Knowledge of developmental changes in children allows us to understand the maturational and degenerative changes of the central nervous system.

Adult↗
PubMed2003

Interhemispheric functional desynchronization in the human vibratory system.

We examined the differences in interhemispheric functional correlation in the somatosensory system using coherence (Coh) analysis. Ten healthy adult volunteers served as subjects for this experiment. Vibratory stimulation (modulation frequency, 21 Hz) was given to each palm to record vibratory steady-state somatosensory evoked potentials (S-SEPs). S-SEPs were recorded from four electrodes placed at 2 cm posterior and anterior to C3 and C4, referred to an electrode at Fpz, respectively. For comparison, unstimulated S-SEPs were also recorded. A total of 50 responses of 1-s epochs was averaged and subjected to discrete fast Fourier transforms to yield the amplitudes of major harmonic components and Coh value. The Coh value between the two signals, x and y at each frequency f, was calculated as [Coh(xy)(f)](2)=[S(xy)(f)](2)/[S(xx)(f)xS(yy)(f)]. The amplitude at 21 Hz in the contralateral somatosensory area was significantly larger than that in the other electrodes. The interhemispheric Coh of the somatosensory area at 21 Hz was significantly lower than that in the unstimulated condition or intrahemispheric Coh. The initial somatosensory information is desynchronized. These findings indicate less significance of interhemispheric correlation as the first step of the vibratory information processing in the somatosensory cortex.

Adult↗