Biomedical subjects

Kazuhiro Shinosaki

Publications and source records attributed to Kazuhiro Shinosaki.

9 recordsLinked to original sources

PubMed2006

Spatially filtered magnetoencephalographic analysis of cortical oscillatory changes in basic brain rhythms during the Japanese 'Shiritori' Word Generation Task.

BACKGROUND: 'Shiritori' (capping verses) is a traditional Japanese word generation game, and is very familiar to native Japanese speakers. The shiritori task is expected to more strongly activate temporal language-related regions than conventional word generation to letters because of its characteristic way to make cue letters. OBJECTIVES: The aim of this study was to examine the cortical oscillatory changes in basic brain rhythms during silently performing a shiritori task. METHODS: Using synthetic aperture magnetometry (SAM) analysis of magnetoencephalography, we estimated the tomographic distributions of the statistically significant differences of the power in the alpha and beta frequency bands between the resting and the task periods. RESULTS: Significant event-related desynchronization (ERD) in the 8- to 25-Hz band, thought to reflect neural activation, was localized within task-related cortical regions with left-side dominance. The significant ERDs were estimated in both the frontal and temporal language-related regions encompassing Broca's and Wernicke's areas, although previous neuroimaging studies using word generation to letters showed neural activation predominantly in frontal regions. CONCLUSIONS: Our results show the potential of SAM analysis for reliable brain mapping of language processing, and suggest that the shiritori task might be more suitable for examining the language-related network in the brain than conventional word generation to letters.

Adult↗

PubMed2005

Information processing flow and neural activations in the dorsolateral prefrontal cortex in the Stroop task in schizophrenic patients. A spatially filtered MEG analysis with high temporal and spatial resolution.

Using a spatially filtered magnetoencephalography analysis (synthetic aperture magnetometry), we estimated neural activations in the Stroop task in nearly real time for schizophrenic patients with/without auditory hallucinations and for normal control subjects. In addition, auditory hallucinations were examined through the information processing flow of the brain neural network, including the frontal regions. One hundred unaveraged magnetoencephalography signals during the incongruent stimulus responses were analyzed with a time window of 200 ms in steps of 50 ms. In the 25-60-Hz band, cortical regions that showed significant current source density changes were examined for each time window. The three groups showed significantly decreased current source density, corresponding to neural activation, with temporal overlap along the fundamental cognitive information processing flow: sensory input system, executive control system, motor output system. Transient neural activations in the dorsolateral prefrontal cortex were bilateral with left-side dominancy for normal controls, left-lateralized for nonhallucinators and right-lateralized for hallucinators. Our results suggest that the dysfunction in the left dorsolateral prefrontal cortex was related to auditory hallucinations, while the information processing flow was unaffected in the schizophrenic subjects in the Stroop task.

Adolescent↗

PubMed2004

Slow repetitive transcranial magnetic stimulation increases somatosensory high-frequency oscillations in humans.

Repetitive transcranial magnetic stimulation (rTMS) has been proposed as a possible treatment for psychiatric and neurological disorders characterized by focal brain excitability, such as major depression and action myoclonus. However, the mechanism of modulating excitability by rTMS is unclear. We examined the changes in high frequency oscillations (HFOs) of somatosensory evoked potentials (SEPs) before and after slow rTMS over the right primary somatosensory cortex (0.5 Hz, 50 pulses, 80% motor threshold intensity). The HFOs, which represent a localized activity of intracortical inhibitory interneurons, were significantly increased after slow rTMS, while the SEPs were not changed. Our results suggest that slow rTMS affects cortical excitability by modulating the activity of the intracortical inhibitory interneurons beyond the time of the stimulation and that rTMS may have therapeutic effects on such disorders.

Adult↗

PubMed2003

Interictal spikes in the fusiform and inferior temporal gyri of an epileptic patient with colored elementary visual auras: a 5-year longitudinal MEG ECD study.

Using equivalent current dipole (ECD) analysis of magnetoencephalography (MEG), we examined the locations of interictal spikes for 5 years in an epileptic patient who had experienced colored elementary visual auras that gradually disappeared with medication. During the period that the patient frequently experienced colored elementary visual auras, six of nine spikes occurred in the right fusiform and inferior temporal gyri. As the frequency of the visual auras decreased, the spikes were widely distributed in the right hemisphere, but were not localized to these areas. After the visual auras ceased, six of seven spikes occurred in the right transverse gyrus of Heschl. These results suggest that colored elementary visual auras of epileptic-positive symptoms originate in the fusiform and inferior temporal gyri and that these regions are involved in human color processing. This is the first MEG study suggesting that the fusiform gyrus and the inferior temporal cortex are related to human color processing.

Adult↗

PubMed2003

[Research strategy for understanding neuronal plasticity and degeneration].

After the disclosure of human genomic information in 2003, the new era of post-genomic research will be in full bloom in the field of neuroscience, brain science as well as in neuropsychiatry. In this paper, the authors discussed possible strategies for understanding neuronal plasticity and neuronal degeneration in the post-genomic research paradigm. Five presentations are discussed in the following orders; 1) pharmacogenomics and epigenetics, 2) neuronal stem cell differentiation and transplantation into brain tissue, 3) Elucidation of the mechanism of neuro-protection and neurogenesis, 4) mechanisms of protein processing, especially importance of regulated intramembranous proteolysis, and 5) simulation analysis of signal transduction pathways. All of these newly developing strategies will be of increasing importance in the research in neuropsychiatry.

Nerve Degeneration↗

PubMed2002

Parallel distributed processing neuroimaging in the Stroop task using spatially filtered magnetoencephalography analysis.

Parallel distributed processing neuroimaging in the Stroop color word interference task in five healthy subjects was studied. The total reaction time was set at 650 ms with a time window of 200 ms in steps of 50 ms. Spatially filtered magnetoencephalography analysis, as used in synthetic aperture magnetometry, was used. Neural activation began in the left posterior parietal-occipital area (150-250 ms post-stimulus), followed by the right prefrontal polar area (250-350 ms), the left dorsolateral prefrontal cortex (250-400 ms), and the mid- to lower- primary motor area (350-400 ms). Successive and temporally overlapping activation of various cortical regions were successfully estimated within a short 200 ms time interval, contrary to previous positron emission tomography and fMRI studies.

Adult↗

PubMed2002

MEG study of long-term cortical reorganization of sensorimotor areas with respect to using chopsticks.

The movements required to use chopsticks are overlearned and routine in Asians. Most non-Asians, on the other hand, typically have difficulty performing this unfamiliar manual activity, and have to focus their attention on the movements required to use chopsticks adequately. Using magnetoencephalography (MEG) we compared the cortical activation of highly trained Asian chopstick users to the activation of Europeans who only occasionally used chopsticks, while they performed the same tasks with chopsticks or a control task of simple tapping of the same fingers. The data were analyzed using the new method of synthetic aperture magnetometry (SAM). In Europeans there was a significantly higher ratio of spectral power in the higher gamma frequency band (60-80 Hz) over the sensorimotor area compared to the Asian subjects. From these results we conclude that the high gamma band activity in the sensorimotor area may reflect focused attention and functional reorganization of the cortical network with respect to sensorimotor experience.

Adult↗

PubMed2001

Landau-Kleffner Syndrome: Localization of Epileptogenic Lesion Using Wavelet- Cross-Correlation Analysis.

Magnetoencephalographic findings in a 6-year-old patient suffering from acquired aphasia with convulsive disorder (Landau-Kleffner Syndrome, LKS) are presented. The data were analyzed using wavelet-cross-correlation analysis, a nonstationary analysis method developed to analyze the localization of an epileptogenic lesion and the propagation of epileptiform discharges. The results indicate that LKS might be a disorder of the primary temporal cortex, and that the auditory neural network may function as the circuit for the epileptic discharge propagation.

Journal Article↗

PubMedDate not supplied

Evaluation of regional cerebral blood flow in fahr disease with schizophrenia-like psychosis: a case report.

We report the case of a patient with Fahr disease presenting with schizophrenia-like psychosis for whom a technetium Tc99 methyl cysteinate dimmer brain study was used to evaluate regional blood flow. A brain single photon-emission CT study showed increased cerebral blood flow to the bilateral temporal lobes. Such perfusion abnormalities may reflect psychotic symptoms, including auditory hallucinations and delusions, which suggests a disruption of the cortico-subcortical neural circuits in psychosis.

Adult↗