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Hideaki Koizumi

Publications and source records attributed to Hideaki Koizumi.

16 recordsLinked to original sources
PubMed2006

Ethical considerations of neuroscience research: the perspectives on neuroethics in Japan.

Recent technologies and developments in neuroscience have contributed to remarkable scientific discoveries, and have also raised many new philosophical, ethical, legal, and social issues. Research in "neuroethics" has identified various ethical issues, which will be difficult for current biomedical ethics to resolve from both an experimental and a social perspective, such as criminal applications of brain scans, incidental findings during non-clinical brain imaging, and cognitive enhancement. Although American and European neuroscience societies have demonstrated immediate, concrete reactions to these ethical issues, including academic conferences, study programs, and publications, Japanese neuroscientists have so far produced little response. Ethics is tightly linked with one's religion, nationality, culture, and social background, whereas science is tightly linked with the demand, economics, and politics of the society to which individuals belong. Taken together, it is important and necessary for Japanese neuroscientists to consider the ethical problems in Japanese neuroscience. In this paper, we first review the history of neuroethics in the world, and then report the less-developed ethical issues in the Japanese neuroscience community, focusing on neuroimaging and manipulative neuroscience as a first step in discussing how to apply principles in neuroethics to this rapidly progressing field of research.

Bioethical Issues↗
PubMed2006

Effect of fMRI acoustic noise on sensorimotor activation examined using optical topography.

Functional magnetic resonance imaging (fMRI) is an important tool for noninvasively imaging the hemodynamic responses accompanying brain activity, but fMRI measurements are accompanied by loud acoustic noises resulting from Lorentz forces that cannot be completely excluded when the present technology is used. We used recorded fMRI acoustic noise and examined its effect on sensorimotor activation in optical topography measurement when subjects were instructed to tap the fingers of the right hand under a 23-dB non-noise condition and 46-, 56-, and 65-dB noise conditions. The results showed that the amplitude of the activation signal (relative change in concentration) for oxygenated hemoglobin in the sensorimotor cortex decreased with increasing noise. The activation signal for deoxygenated hemoglobin did not depend significantly on the noise level but did tend to decrease with increasing noise. These results suggest that fMRI acoustic noise affects the hemodynamics of cortical areas associated with the processing of information other than auditory information.

Adult↗
PubMed2005

Effects of alcohol on hemodynamic and cardiovascular reaction in different genotypes.

This study assessed hemodynamic changes associated with alcohol intake in people who have different sensitivities to alcohol due to an inactive form of mitochondrial aldehyde dehydrogenase (ALDH). People with ALDH2*1/*2 are more sensitive to alcohol than people with ALDH2*1/*1. Six ALDH2*1/*1 subjects and four ALDH2*1/*2 subjects participated in this study. The subjects drank whisky with water (0.4 ml/kg of ethanol). Optical topography (Hitachi Medical Corporation: ETG-100) was used to measure hemodynamic changes in an occipital region during visual stimulation. Hemodynamic changes, heart rate, mean blood pressure, and reaction time were measured 20 min before, immediately after, and 20, 40, and 60 min after alcohol intake. Breath-alcohol concentration was measured at each of the assessment points. After alcohol intake, the hemodynamic peak value, peak time, reaction time, and heart rate of the ALDH2*1/*2 subjects differed from those of the ALDH2*1/*1 subjects. The hemodynamic peak value and reaction time gradually increased 60 min after alcohol exposure, and the peak time was shortest 20 min after alcohol intake. These results might reflect different acetaldehyde levels causing changes in the reactivity of the vascular smooth muscle and cerebral activity in the visual cortex.

Aldehyde Dehydrogenase↗
PubMed2004

Prefrontal cortical activation associated with working memory in adults and preschool children: an event-related optical topography study.

It is well known that lateral areas of the prefrontal cortex (LPFC) play a central role in working memory (a critical basis of various cognitive functions), but it remains unknown whether the LPFC of children of preschool age is responsible for working memory. To address this issue, we adopted a recently developed non-invasive imaging technique, optical topography (OT), which can potentially be applied to functional mapping in childhood. We firstly examined changes of activity in the LPFC using OT while adult subjects performed an item-recognition task, which requires working memory, under different memory-load conditions. We observed activation in the bilateral LPFC during performance of this task, the magnitude of which differed depending on memory-load. Then, we applied the same technique on 5- and 6-year-old children and observed the activation associated with working memory in the LPFC. Areas and properties of such activity were similar in adults and preschool children. Thus, for the first time, we demonstrate that the LPFC of preschoolers is active during working memory processes, indicating that in 5- and 6-year-old children, the LPFC has already developed processing of this important cognitive function.

Adult↗
PubMed2004

The concept of 'developing the brain': a new natural science for learning and education.

From the viewpoint of biology, learning and education can be defined as the processes of forming neuronal connections in response to external environmental stimuli, and of controlling or adding appropriate stimuli, respectively. Learning and education can thus be studied as a new field of natural sciences with the entire human life span as its subject, thus including various problems such as fetal environment, childcare, language acquisition, general/special education, and rehabilitation. Non-invasive imaging of higher-order brain functions in humans will clarify the brain's developmental processes, and will provide various evidence for learning sciences. This new approach is called 'developing the brain' or 'brain science and education'. The origin of the concept and its present state are described and its future prospects are briefly analyzed.

Brain↗
PubMed2003

Sounds and silence: an optical topography study of language recognition at birth.

Does the neonate's brain have left hemisphere (LH) dominance for speech? Twelve full-term neonates participated in an optical topography study designed to assess whether the neonate brain responds specifically to linguistic stimuli. Participants were tested with normal infant-directed speech, with the same utterances played in reverse and without auditory stimulation. We used a 24-channel optical topography device to assess changes in the concentration of total hemoglobin in response to auditory stimulation in 12 areas of the right hemisphere and 12 areas of the LH. We found that LH temporal areas showed significantly more activation when infants were exposed to normal speech than to backward speech or silence. We conclude that neonates are born with an LH superiority to process specific properties of speech.

Humans↗
PubMed2003

Brain imaging in awake infants by near-infrared optical topography.

Studies of young infants are critical to understand perceptual, motor, and cognitive processing in humans. However, brain mechanisms involved are poorly understood, because the use of brain-imaging methods such as functional magnetic resonance imaging in awake infants is difficult. In the present study we show functional brain imaging of awake infants viewing visual stimuli by means of multichannel near-infrared spectroscopy, a technique that permits a measurement of cerebral hemoglobin oxygenation in response to brain activation through the intact skull without subject constraint. We found that event-related increases in oxyhemoglobin were evident in localized areas of the occipital cortex of infants aged 2-4 months in response to a brief presentation of a checkerboard pattern reversal while they maintained fixation to attention-grabbing stimuli. The dynamic change in cerebral blood oxygenation was qualitatively similar to that observed in the adult brain. This result introduces near-infrared optical topography as a method for investigating the functional development of the brain in early infancy.

Brain↗
PubMed2003

Acute effects of alcohol on hemodynamic changes during visual stimulation assessed using 24-channel near-infrared spectroscopy.

The purpose of this study was to evaluate the effects of alcohol on hemodynamic changes induced by visual stimulation. Ten healthy human subjects were examined using Optical Topography((R)) (Hitachi Medical Corporation: ETG-100). Each subject gradually drank 0.4 ml/kg alcohol over 10 min. Changes in oxy-hemoglobin (Hb), deoxy-Hb and total-Hb concentration were measured five times: 20 min before alcohol intake, immediately after alcohol intake, and at 20, 40 and 60 min after alcohol intake. A questionnaire was used to assess subjective feelings of alcohol. Blood-alcohol concentration (BAC) was estimated from ethanol concentration in expired air four times: immediately after alcohol intake and at 20, 40 and 60 min after alcohol intake. The visual stimulation tool was a checkerboard. It showed alternations of black and red patterns at a frequency of 8 Hz. The stimulus was displayed for 10 s after a rest of 30 s. The stimulus was repeated 10 times. Oxy-Hb concentration increased and deoxy-Hb concentration decreased during visual stimulation before and after alcohol intake, despite changes in the score of subjective feelings of alcohol and BAC. Alcohol intake does not significantly affect hemodynamic changes caused by visual stimulation in the visual cortex.

Adult↗
PubMed2003

Optical topography: practical problems and new applications.

We will briefly review the present status of optical topography and then discuss the method of improving practicality, i.e., the signal-to-noise (S/N) ratio and the spatial resolution in observations of higher-order brain functions. The optimum wavelength pair improved the S/N ratio sixfold for deoxyhemoglobin, and new configurations of light irradiation and detection positions doubled the spatial resolution. We also report on developing application fields of optical topography. This modality will bridge the gap between natural sciences, neuroscience, and pedagogy, and show actual real-time brain activity.

Brain↗
PubMed2002

Arranging optical fibres for the spatial resolution improvement of topographical images.

Optical topography is a method for visualization of conical activity. Ways of improving the spatial resolution of the topographical image with three arrangements of optical fibres are discussed. A distribution of sensitivity is obtained from the phantom experiment, and used to reconstruct topographical images of an activation area of the brain with the fibres in each arrangement. The correlations between the activated area and the corresponding topographical images are obtained, and the effective arrangement of the optical fibres for improved resolution is discussed.

Brain↗
PubMed2002

Non-invasive assessment of language lateralization by transcranial near infrared optical topography and functional MRI.

Near infrared optical topography (OT) is the simultaneous acquisition of hemoglobin absorption from an array of optical fibers on the scalp to construct maps of cortical activity. We demonstrate that OT can be used to determine lateralization of prefrontal areas to a language task that has been validated by functional MRI (fMRI). Studies were performed on six subjects using a visually presented language task. Laterality was quantified by the relative number of activated pixels in each hemisphere for fMRI, and the total hemoglobin responses in each hemisphere for OT. All subjects showed varying degrees of left hemisphere language dominance and the mean laterality indices for subjects who underwent both OT and fMRI were in good agreement. These studies demonstrate that OT gives predictions of hemispheric dominance that are consistent with fMRI. Due to the ease of use and portable nature of OT, it is anticipated that optical topography will be valuable tool for neurological examinations of cognitive function.

Adult↗
PubMed2002

Simultaneous recording of event-related auditory oddball response using transcranial near infrared optical topography and surface EEG.

Near infrared optical topography (OT) is the measurement of hemoglobin absorption simultaneously from an array of optical fibers on the scalp to construct maps of cortical activity. We demonstrate that OT can be used to simultaneously detect and characterize the hemodynamic responses associated with an "oddball" auditory stimulus and that corresponding electrical event related potentials can be acquired simultaneously using conventional scalp recordings. In addition to the measured electrical response, the hemodynamic localization is consistent with fMRI studies, which show significant activation in the temporal and parietal cortical regions. The event-related response of total hemoglobin showed relatively slow peak latencies (5.8 +/- 0.3 s), which were also consistent with fMRI. The current study shows the regions of peak hemodynamic activity that are in closest proximity to areas of peak electrical activity. This is the first demonstration of simultaneous ERP electrical recording and non-invasive optical mapping in human subjects, which promises to be an important tool in the characterization of both normal and abnormal brain function.

Auditory Cortex↗
PubMed2002

Near-infrared spectroscopic topography as a tool to monitor motor reorganization after hemiparetic stroke: a comparison with functional MRI.

BACKGROUND AND PURPOSE: Motor functional recovery from stroke can occur, but the mechanisms underlying this restorative process remain to be elucidated. We used near-infrared spectroscopic (NIRS) topography in comparison with functional MRI (fMRI) to evaluate the compensatory motor activation of cortical regions in patients who recovered from hemiparesis after cortical cerebral infarction. METHODS: We examined 6 right-handed patients who suffered cerebral infarction of the middle cerebral artery territory with minimal or mild residual contralateral hemiparesis (4 men and 2 women, 59 to 79 years old, all had left hemiparesis). Both fMRI and NIRS were studied during a hand movement task at chronic stages. Five right-handed, normal subjects (3 men and 2 women, 44 to 81 years old) served as controls. RESULTS: fMRI and NIRS detected very similar cerebral cortical activation, although NIRS detected only superficial activation. The spatial resolution of NIRS was less than that of fMRI, but NIRS provided a dynamic profile of activation. Normal subjects activated predominantly the contralateral primary sensorimotor cortex and supplementary motor areas during each hand movement. All the stroke patients exhibited the normal activation pattern during normal hand movement. On affected hand movement, the stroke patients showed extended activation not only in the contralateral motor cortex but also in the ipsilateral motor cortex (primary motor cortex and supplementary motor areas). CONCLUSIONS: Both fMRI and NIRS studies provided evidence for the contribution of ipsilateral motor cortical compensation or reorganization to the recovery from poststroke hemiparesis. The result demonstrated that NIRS was a unique tool to monitor poststroke alterations in cortical motor functions.

Adaptation, Physiological↗
PubMedDate not supplied

Intersubject variability of near-infrared spectroscopy signals during sensorimotor cortex activation.

We investigate the intersubject signal variability of near-infrared spectroscopy (NIRS), which is commonly used for noninvasive measurement of the product of the optical path length and the concentration change in oxygenated hemoglobin (DeltaC'oxy) and deoxygenated hemoglobin (DeltaC'deoxy) and their sum (DeltaC'total) related to human cortical activation. We do this by measuring sensorimotor cortex activation in 31 healthy adults using 24-measurement-position near-infrared (NIR) topography. A finger-tapping task is used to activate the sensorimotor cortex, and significant changes in the hemisphere contralateral to the tapping hand are assessed as being due to the activation. Of the possible patterns of signal changes, 90% include a positive DeltaC'oxy, 76% included a negative DeltaC'deoxy, and 73% included a positive DeltaC'total. The DeltaC'deoxy and DeltaC'total are less consistent because of a large intersubject variability in DeltaC'deoxy; in some cases there is a positive DeltaC'deoxy. In the cases with no positive DeltaC'oxy in the contralateral hemisphere, there are cases of other possible changes for either or both hemispheres and no cases of no change in any hemoglobin species in either hemisphere. These results suggest that NIR topography is useful for observing brain activity in most cases, although intersubject signal variability still needs to be resolved.

Adult↗
PubMedDate not supplied

Within-subject reproducibility of near-infrared spectroscopy signals in sensorimotor activation after 6 months.

Near-infrared spectroscopy (NIRS) can measure the product of the optical path length and the concentration change in oxygenated hemoglobin (DeltaC'oxy), deoxygenated hemoglobin (DeltaC'deoxy), and their sum (DeltaC'total) in the human cerebral cortex, and it has been used for noninvasive investigation of human brain functions. We evaluate the within-subject reproducibility of the NIRS signals by repeated measurement of the sensorimotor cortex in healthy adults taken over a period of about 6 months using near-infrared (NIR) topography. The maximum signal amplitudes and the location of activation centers are compared between two sessions for each subject. The signal amplitudes vary between sessions and no consistent tendency in the changes is found among subjects. However, the distance between the activation centers identified in two sessions is relatively small, within 20 mm on average across subjects, which is comparable to the smallest distance between measurement positions in the NIR topography (21 mm). Moreover, within-subject comparisons of signal time courses show high correlation coefficients (>0.8) between the two sessions. This result, demonstrating a high within-subject reproducibility of the temporal information in NIRS signals, particularly contributes to the development of a new application of NIRS.

Adult↗