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Fumihiko Okada

Bio: Fumihiko Okada is an academic researcher from Hokkaido University. The author has contributed to research in topics: Cyclase & Adenylate kinase. The author has an hindex of 13, co-authored 49 publications receiving 650 citations.

Papers
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Journal ArticleDOI
TL;DR: Observations suggest an application for NIRS in psychiatric disease management, as an addition to clinical monitoring at the bedside, and time resolved 64-channel optical imaging system was constructed.
Abstract: Changes in cerebral blood flow (CBF) and cerebral metabolic rates (CMRO2) have been used as indices for changes in neuronal activity. Near–infrared spectroscopy (NIRS) can also measure cerebral haemodynamics and metabolic changes, enabling the possible use of multichannel recording of NIRS for functional optical imaging of human brain activity. Spatio–temporal variations of brain regions were demonstrated during various mental tasks. Non–synchronous behaviour of cerebral haemodynamics during the neuronsl activation was observed. Gender– and handedness–dependent lateralization of the function between right and left hemispheres was demonstrated by simultaneous measurement using two NIR instruments during the mirror–drawing task. A lack of interhemispheric integration was observed with schizophrenic patients. These observations suggest an application for NIRS in psychiatric disease management, as an addition to clinical monitoring at the bedside. A time–resolved 64–channel optical imaging system was constructed. This consisted of three picosecond laser diodes and 64 channels of TAC and CFD systems. Image reconstruction for phantom model systems was performed. Time–resolved quantitative optical imaging will become real in the very near future.

93 citations

Journal ArticleDOI
TL;DR: Patients with major depression diagnosed by DSM-III-R are examined to find and qualify disturbances in brain oxygenation and hemodynamics during a psychological task, finding the nominally 'nondominant' hemisphere may become dominant during the course of depression.

72 citations

Journal ArticleDOI
TL;DR: Patients with chronic schizophrenia are examined to find and qualify disturbances in interhemispheric integration in brain oxygen metabolism and hemodynamics during a psychological task and certain schizophrenic symptoms may be related to defective interhemisphere integration.
Abstract: We examined 38 patients with chronic schizophrenia to find and qualify disturbances in interhemispheric integration in brain oxygen metabolism and hemodynamics during a psychological task. A group of thirty-eight age- and sex-matched healthy volunteers were monitored as controls. Multi channel near-infrared (NIR) spectrophotometry was used to observed real-time alterations in cerebral oxygenation in areas of both hemispheres of the forebrain adjacent to the forehead during the mirror drawing task (MDT). In response to MDT normal volunteers showed distinct and well-integrated patterns of changes in oxygenated hemoglobin Hb, deoxygenated Hb, and blood volume total Hb. On the other hand, half the schizophrenics showed dysregulated patterns between hemispheres which never appeared in normal volunteers. Certain schizophrenic symptoms may be related to defective interhemispheric integration.

71 citations

Journal ArticleDOI
TL;DR: Functional uncoupling of the N protein from receptors was responsible for early development of desensitization of β‐adrenergic receptor‐mediated adenylate cyclase in the cerebral cortex during desipramine therapy.
Abstract: Continuous treatment (1-10 days) of rats with desipramine (10 mg/kg, twice per day) caused desensitization of the beta-adrenergic receptor-coupled adenylate cyclase system of cerebral cortical membranes. The decrease in the isoproterenol-stimulated adenylate cyclase activity was more rapid and greater than the decrease in the number of beta-adrenergic receptors in membranes during treatment of the membrane donor rats with desipramine, indicating that the desensitization occurring at an early stage of the treatment was not accounted for solely by the decrease in the receptor number. Neither the guanine nucleotide regulatory protein (N) nor the adenylate cyclase catalyst was impaired by the drug treatment, since there was no decrease in the cyclase activity measured in the presence or absence of GTP, guanyl-5'-yl-beta-gamma-imidodiphosphate [Gpp(NH)p], NaF, or forskolin. Gpp(NH)p-induced activation of membrane adenylate cyclase developed with a lag time of a few minutes in membranes from control or drug-treated rats. The lag was shortened by the addition of isoproterenol, indicating that beta-receptors were coupled to N in such a manner as to facilitate the exchange of added Gpp(NH)p with endogenous GDP on N. This effect of isoproterenol rapidly decreased during the drug treatment of rats. Thus, functional uncoupling of the N protein from receptors was responsible for early development of desensitization of beta-adrenergic receptor-mediated adenylate cyclase in the cerebral cortex during desipramine therapy.

60 citations

Journal ArticleDOI
TL;DR: NIR results showed that a large majority of women used both sides of the brain when concentrating on carrying out the MDT, whilst most men, especially left-handers, reacted mainly using the hemisphere which was 'dominant' according to handedness.

53 citations


Cited by
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Journal ArticleDOI
TL;DR: A brief historical overview of the events that have shaped the present status of fNIRS is presented, including the introduction of the commercial multi-channel systems, recent commercial wireless instrumentation and more advanced prototypes.

1,637 citations

Journal ArticleDOI
TL;DR: First near-infrared imaging devices are being applied successfully for low-resolution functional brain imaging andvantages of the optical methods include biochemical specificity, a temporal resolution in the millisecond range, the potential of measuring intracellular and intravascular events simultaneously and the portability of the devices enabling bedside examinations.

1,602 citations

Journal ArticleDOI
TL;DR: The practical implementation of various signal processing techniques for removing physiological, instrumental, and motion-artifact noise from optical data are described within the context of the MATLAB-based graphical user interface program, HomER, which is developed and distributed to facilitate the processing of optical functional brain data.
Abstract: Near-infrared spectroscopy (NIRS) is a noninvasive neuroimaging tool for studying evoked hemodynamic changes within the brain. By this technique, changes in the optical absorption of light are recorded over time and are used to estimate the functionally evoked changes in cerebral oxyhemoglobin and deoxyhemoglobin concentrations that result from local cerebral vascular and oxygen metabolic effects during brain activity. Over the past three decades this technology has continued to grow, and today NIRS studies have found many niche applications in the fields of psychology, physiology, and cerebral pathology. The growing popularity of this technique is in part associated with a lower cost and increased portability of NIRS equipment when compared with other imaging modalities, such as functional magnetic resonance imaging and positron emission tomography. With this increasing number of applications, new techniques for the processing, analysis, and interpretation of NIRS data are continually being developed. We review some of the time-series and functional analysis techniques that are currently used in NIRS studies, we describe the practical implementation of various signal processing techniques for removing physiological, instrumental, and motion-artifact noise from optical data, and we discuss the unique aspects of NIRS analysis in comparison with other brain imaging modalities. These methods are described within the context of the MATLAB-based graphical user interface program, HomER, which we have developed and distributed to facilitate the processing of optical functional brain data.

1,174 citations

Journal ArticleDOI
TL;DR: The theoretical basis for near-infrared or diffuse optical spectroscopy (NIRS or DOS) is developed, and the basic elements of diffuse optical tomography (DOT) are outlined.
Abstract: This review describes the diffusion model for light transport in tissues and the medical applications of diffuse light. Diffuse optics is particularly useful for measurement of tissue hemodynamics, wherein quantitative assessment of oxy- and deoxy-hemoglobin concentrations and blood flow are desired. The theoretical basis for near-infrared or diffuse optical spectroscopy is developed, and the basic elements of diffuse optical tomography are outlined. We also discuss diffuse correlation spectroscopy, a technique whereby temporal correlation functions of diffusing light are transported through tissue and are used to measure blood flow. Essential instrumentation is described, and representative brain and breast functional imaging and monitoring results illustrate the workings of these new tissue diagnostics.

987 citations

Journal ArticleDOI
TL;DR: It is found that, while diffuse optics can provide substantial advantages to the psychiatric researcher relative to the alternative brain imaging methods, the method remains substantially underutilized in this field.

888 citations