Biomedical subjects

Masuro Shintani

Publications and source records attributed to Masuro Shintani.

8 recordsLinked to original sources

PubMed2006

Cerebral cortical dysfunction in patients with temporomandibular disorders in association with jaw movement observation.

Temporomandibular disorders (TMD) represent a group of chronic painful conditions in the masticatory musculature and temporomandibular joint. To examine possible changes in cortical machinery in TMD patients, we compared neuromagnetic signals evoked by cortical neurons between healthy subjects and TMD patients while they were carefully observing the video frames of jaw-opening movements performed by another person. During the movement observation task in the healthy subjects, we found cortical activation in the following sequence with left hemisphere dominance: (1) the occipitotemporal region near the inferior temporal sulcus (human homologue of MT/V5 in monkeys), (2) the inferior parietal cortex (IPC), and (3) the anterior part of the inferior-lateral precentral gyrus (PrCG). In the TMD patients, however, we found deficit or marked attenuation of the neuromagnetic responses in the PrCG and IPC, while the activity of the MT/V5 showed no differences from that in the healthy subjects. In addition, we could not find any differences in cortical magnetic responses between healthy subjects and TMD patients when they were observing palm-opening movements, indicating that cortical dysfunction associated with jaw-movement observation is specific phenomena in the patients of TMD. Thus the present study provides new neuropathological evidence that TMD patients exhibit dysfunction of recognition mechanisms in cerebral cortex during motor observation, and suggests that disturbance of cortical functions regulating visuomotor integration would play a crucial role in development as well as aggravation of TMD.

Adult↗

PubMed2006

Cortical reorganization and somatic delusional psychosis: a magnetoencephalographic study.

A woman complained of feeling a "metal-like thing" in her oral cavity 4 years after a stroke. She was convinced of the physical nature of her complaint despite intact dental and neurological findings. Somatosensory evoked magnetic fields suggested that her decreased right SII function was compensated for by the right SI region, probably contributing to the delusional symptom.

Cerebral Cortex↗

PubMed2004

An earlier component of face perception detected by seeing-as-face task.

To investigate the time sequence of the neural processes underlying face perception, magnetoencephalography was performed using a seeing-as-face task, in which visual inputs were identical across two conditions, but subject perceptions differed: one being a non-specific pattern of geographical shapes, the other being a percept of a face. Subtraction between the two conditions revealed a response occurring 120 ms after stimulus onset in right occipital, approximately 50 ms earlier than previously reported response at a latency of 170 ms at the right fusiform gyrus. As our novel task completely excluded differences in low-level properties of visual stimuli between control and face conditions, these two responses were considered specific to face perception. The result supported the two-stage theory of face processing.

Adult↗

PubMed2004

Evaluation of missing fundamental phenomenon in the human auditory cortex.

OBJECTIVE: Harmonic complex tones consisting of four or more continuous harmonics of a certain stem frequency are perceived as the pitch of the fundamental frequency tone, it is referred to as the missing fundamental phenomenon (MFP). It is considered that the MFP is produced in the central auditory system, not in the periphery. However, it remains unclear where and how complex sounds is integrated. Using 306ch magnetoencephalography (MEG), we investigated when and where the MFP was integrated in the auditory cortex. METHOD: We examined six subjects who were selected by MEG in 12 healthy right-handed adult volunteers with normal auditory sensation. Ears were randomly stimulated with five different complex tones consist of fundamental frequency tone and harmonic complex tones. The location and direction of equivalent current dipoles (ECD) were evaluated at P50 and N100 in the right temporal lobe by MEG. Dispersion of the source of ECD was respectively evaluated on their brain MRI. RESULTS: Stimulation of ears with harmonic complex tones and the stem frequency tone revealed the localization of P50 and N100 ECD in the transverse temporal gyrus and their peripheral superior temporal gyrus. Although the sources of P50 ECD for harmonic complex tones and the fundamental tone were varied around the transverse temporal gyrus and superior temporal gyrus, the sources of N100 ECD were almost identical at the transverse temporal gyrus, demonstrating the MFP. This phenomenon were similarly observed, even when dichotic listening were stimulated. CONCLUSION: These findings suggest that the MFP occurs in the transverse temporal gyrus and the superior temporal gyrus, which are the primary auditory cortex, between P50 and N100.

Acoustic Stimulation↗

PubMed2004

Face area representation of primary somatosensory cortex in humans identified by whole-head magnetoencephalography.

The feasibility of precise mapping was investigated noninvasively on the face component in predominantly unilateral primary somatosensory cortices (SI) in six healthy subjects. We recorded somatosensory evoked magnetic fields (SEFs) from the SI and secondary somatosensory cortices (SII) following the electrical stimulation of six skin sites: the infraorbital foramen, the angle of mouth, the upper lip, the lower lip, the mental foramen, and the mandibular angle. The median nerve at the wrist was stimulated as a standard of the map. The location of the equivalent current dipoles (ECDs) estimated from the distribution of magnetic fields was identified on MR images of the brain on each subject. The ECDs of the early components of SEF with peaks of 20-30 ms aligned along the SI in the hemisphere contralateral to the stimulation site. Late components with peaks of 80-150 ms were recorded from the bilateral hemispheres, and their ECDs were identified in the SII of the bilateral hemispheres. There was a distinct separation between the ECD locations representing discrete sites on the face and thumb in the SI of the contralateral hemisphere. Five sites of the face area in SI at the contralateral hemisphere were compatible with the conventional arrangement of homunculus in one subject. However, the remaining subjects had variations in the arrangement. The face area reorganization in the SI is possible to be related to the use-dependent cortical plasticity of the individual or to the perceptual experience by vision and proprioception.

Adult↗

PubMed2003

Magnetoencephalographic study of the starting point of voluntary swallowing.

Clear findings relative to where in the brain the starting point of voluntary swallowing is controlled were obtained in the present magnetoencephalographic study. Namely, the cerebral activity was observed in the cingulate gyrus and supplementary motor area for about 80 ms between 1,000 and 1,500 ms before swallowing in all test subjects. Thus, it is clear that this type of central control mechanism also plays an important role in complicated swallowing movements.

Adult↗

PubMed2002

Visual protective sheet can increase blink rate while playing a hand-held video game.

PURPOSE: To evaluate the effectiveness of a protective sheet in reducing eye strain caused by unnecessary light reflection on portable liquid crystal display panels while playing Game Boy (Nintendo, Kyoto, Japan). DESIGN: Nonrandomized clinical trial. METHODS: The blink rates of 24 normal volunteers were measured under relaxed conditions while viewing a portable liquid crystal display panel and playing Game Boy with and without the protective sheet of polyethylene terephthalate with antiglare coating for a total of 10 minutes each. RESULTS: The results showed a dramatic increase (from 5.6 +/- 3 to 9.1 +/- 4.9 [P <.0001]) in blinks/minute with use of the protective sheet. CONCLUSION: The protective sheet has shown the possibility of increasing the blink rate by making the screen easier to see.

Adult↗

PubMed2002

Experimental device for detecting laryngeal movement during swallowing.

It has been reported that swallowing is a rhythmic movement, in which the onset of the oro-pharyngeal stage of swallowing starts from the mylohyoid muscle, followed by movement of the oral and pharyngeal muscles, and reaching the superior esophageal sphincter muscle. This is defined as the oro-pharyngeal stage of swallowing. It has also been reported that along with this movement, the larynx elevates in an antero-superior direction. To investigate the swallowing movement, it would be useful to be able to detect the start of swallowing movements from the body surface. Such a device was designed in this study to investigate the relationships between the onset of laryngeal movement and the EMG initiation of the anterior digastric muscle. Although experimental conditions must be further examined, we were able to record the reproducible movement and the position of larynx using our device provides another tool for studying the swallowing movement.

Deglutition↗