Biomedical subjects

R Kawashima

Publications and source records attributed to R Kawashima.

At least 19 recordsLinked to original sources

PubMed2007

Nonlinear local electrovascular coupling. II: From data to neuronal masses.

In the companion article a local electrovascular coupling (LEVC) model was proposed to explain the continuous dynamics of electrical and vascular states within a cortical unit. These states produce certain mesoscopic reflections whose discrete time series can be reconstructed from electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). In this article we develop a recursive optimization algorithm based on the local linearization (LL) filter and an innovation method to make statistical inferences about the LEVC model from both EEG and fMRI data, i.e., to estimate the unobserved states and the unknown parameters of the model. For a better understanding, the LL filter is described from a Bayesian point of view, providing the particulars for the case of hybrid data (e.g., EEG and fMRI), which could be sampled at different rates. The dynamics of the exogenous synaptic inputs going into the cortical unit are also estimated by introducing a set of Gaussian radial basis functions. In order to study the dynamics of the electrical and vascular states in the striate cortex of humans as well as their local interrelationships, we applied this algorithm to EEG and fMRI recordings obtained concurrently from two subjects while passively observing a radial checkerboard with a white/black pattern reversal. The EEG and fMRI data from the first subject was used to estimate the electrical/vascular states and parameters of the LEVC model in V1 for a 4.0 Hz reversion frequency. We used the EEG data from the second subject to investigate the changes in the dynamics of the electrical states when the frequency of reversion is varied from 0.5-4.0 Hz. Then we made use of the estimated electrical states to predict the effects on the vasculature that such variations produce.

Bayes Theorem↗

PubMed2005

Fusing EEG and fMRI based on a bottom-up model: inferring activation and effective connectivity in neural masses.

The elucidation of the complex machinery used by the human brain to segregate and integrate information while performing high cognitive functions is a subject of imminent future consequences. The most significant contributions to date in this field, known as cognitive neuroscience, have been achieved by using innovative neuroimaging techniques, such as electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI), which measure variations in both the time and the space of some interpretable physical magnitudes. Extraordinary maps of cerebral activation involving function-restricted brain areas, as well as graphs of the functional connectivity between them, have been obtained from EEG and fMRI data by solving some spatio-temporal inverse problems, which constitutes a top-down approach. However, in many cases, a natural bridge between these maps/graphs and the causal physiological processes is lacking, leading to some misunderstandings in their interpretation. Recent advances in the comprehension of the underlying physiological mechanisms associated with different cerebral scales have provided researchers with an excellent scenario to develop sophisticated biophysical models that permit an integration of these neuroimage modalities, which must share a common aetiology. This paper proposes a bottom-up approach, involving physiological parameters in a specific mesoscopic dynamic equations system. Further observation equations encapsulating the relationship between the mesostates and the EEG/fMRI data are obtained on the basis of the physical foundations of these techniques. A methodology for the estimation of parameters from fused EEG/fMRI data is also presented. In this context, the concepts of activation and effective connectivity are carefully revised. This new approach permits us to examine and discuss some future prospects for the integration of multimodal neuroimages.

Brain↗

PubMed2004

fMRI activation maps based on the NN-ARx model.

The most significant progresses in the understanding of human brain functions have been possible due to the use of functional magnetic resonance imaging (fMRI), which when used in combination with other standard neuroimaging techniques (i.e., EEG) provides researchers with a potential tool to elucidate many biophysical principles, established previously by animal comparative studies. However, to date, most of the methods proposed in the literature seeking fMRI signs have been limited to the use of a top-down data analysis approach, thus ignoring a pool of physiological facts. In spite of the important contributions achieved by applying these methods to actual data, there is a disproportionate gap between theoretical models and data-analysis strategies while trying to focus on several new prospects, like for example fMRI/EEG data fusion, causality/connectivity patterns, and nonlinear BOLD signal dynamics. In this paper, we propose a new approach which will allow many of the abovementioned hot topics to be addressed in the near future with an underlying interpretability based on bottom-up modeling. In particular, the theta-MAP presented in the paper to test brain activation corresponds very well with the standardized t test of the SPM99 toolbox. Additionally, a new Impulse Response Function (IRF) has been formulated, directly related to the well-established concept of the hemodynamics response function (HRF). The model uses not only the information contained in the signal but also that in the structure of the background noise to simultaneously estimate the IRF and the autocorrelation function (ACF) by using an autoregressive (AR) model with a filtered Poisson process driving the dynamics. The short-range contributions of voxels within the near-neighborhood are also included, and the potential drift was characterized by a polynomial series. Since our model originated from an immediate extension of the hemodynamics approach [Friston, K.J., Mechelli, A., Turner, R., Price C.J. (2000a). Nonlinear responses in fMRI: the balloon model, volterra kernels, and other hemodynamics. NeuroImage 12, 466-477.], a natural interpretability of the results is feasible.

Algorithms↗

PubMed2003

TNF combined with IFN-alpha accelerates NF-kappaB-mediated apoptosis through enhancement of Fas expression in colon cancer cells.

Immunostaining and EMSA revealed that NF-kappaB was activated strongly by TNF/IFN-alpha compared to TNF alone in a human colon adenocarcinoma cell line, RPMI4788. Although inhibition of activated NF-kappaB, by using an NF-kappaB decoy, reduced cell viability after treatment with TNF only, NF-kappaB decoy resulted in recovery of cell viability after TNF/IFN-alpha treatment. Caspase-3 activity was increased in cells induced by TNF/IFN-alpha, while suppression of caspase-3 activity was observed in cells transfected with NF-kappaB decoy and then treated by TNF/IFN-alpha. On the other hand, Fas expression was strongly enhanced by TNF/IFN-alpha, and inhibition of TNF/IFN-alpha-induced NF-kappaB activation, by using NF-kappaB decoy, decreased Fas expression. Cell viability and caspase-3 activity decreased in cells treated with TNF/IFN-alpha and anti-FasL antibody. Taken together, our findings suggest that activated NF-kappaB induced by the crosstalk between TNF and IFN-alpha is a novel pro-apoptotic signal acting via enhancement of Fas expression.

Antibodies↗

PubMed2002

Brain activation during the fist-edge-palm test: a functional MRI study.

The purpose of our study is to clarify, using functional MRI, brain regions activated during the fist-edge-palm task (FEP) compared to relatively simple hand motor tasks using either the right or the left hand in right-handed normal volunteers. The FEP was introduced to detect a disorder of voluntary movement, and it is believed to be closely related to contralateral frontal lobe damage. However, this assumption still remains controversial. Ten subjects participated in this study. Hand motor tasks were as follows: (1) the FEP, in which the subjects were requested to place their hand in three different positions sequentially: a fist resting horizontally, a palm resting vertically, and a palm resting horizontally; (2) a fist-palm task (FP), in which the subjects were asked to clench and unclench their fist alternately; and (3) a control task requiring the subjects to knock lightly with their clenched fist. The contralateral sensomotor and premotor areas were activated in the FP with the right hand and the contralateral sensorimotor, premotor, and supplementary motor areas (SMA) were activated in the FP with the left hand. In the FEP with either hand, bilateral premotor and left parietal areas and ipsilateral cerebellum were also activated as well as contralateral sensorimotor area and SMA. Our results suggest that successful performance of the FEP requires the participation of more brain areas than FP, which may explain why some patients without frontal lobe damage failed to perform the FEP.

Adult↗

PubMed2001

Hypoperfusion in the supplementary motor area, dorsolateral prefrontal cortex and insular cortex in Parkinson's disease.

The changes of regional cerebral blood flow (rCBF) in Parkinson's disease (PD) were investigated. Because of individual differences in brain volume and the extent of brain atrophy, previous functional imaging studies involved potential methodological difficulties. In this study, using the statistical parametric mapping technique, 99mTechnetium-labeled hexamethylpropyleneamineoxime brain single-photon emission computed tomography images from 18 patients with PD were transformed into standard brain-based stereotaxic coordinate spaces and then compared with such images for 11 control subjects matched for age and extent of brain atrophy. A rCBF decrement in the supplementary motor area (SMA) and such decrement in the dorsolateral prefrontal cortex (DLPFC) were observed in the summarized PD images as compared with controls (p<0.005). In a subgroup in the Hoehn-Yahr III/IV stage (11 cases), the rCBF decrement was demonstrated not only in the SMA, but also in the DLPFC and insular cortex (p<0.001). There was a correlation between the degree of the rCBF decrement in the DLPFC or the insular cortex and the score of the unified Parkinson's disease rating scale (p<0.05), while the rCBF decrement in the SMA showed no relationship with the severity of disease. The function of the SMA is closely associated with the nigro-striatal pathway and its impairment can explain the basic akinetic symptoms in PD, which are responsive to L-DOPA treatment. On the other hand, the DLPFC and insular cortex may play key roles in specific symptoms of impairment at advanced stages, such as impaired working memory, postural instability and autonomic dysfunction. We hypothesize that the impairment of the DLPFC and insular function is correlated with the progression of the disease and is related to DOPA-refractory symptoms, which are major problems in the care of patients with advanced PD.

Adult↗

PubMed2001

A probabilistic atlas and reference system for the human brain: International Consortium for Brain Mapping (ICBM).

Motivated by the vast amount of information that is rapidly accumulating about the human brain in digital form, we embarked upon a program in 1992 to develop a four-dimensional probabilistic atlas and reference system for the human brain. Through an International Consortium for Brain Mapping (ICBM) a dataset is being collected that includes 7000 subjects between the ages of eighteen and ninety years and including 342 mono- and dizygotic twins. Data on each subject includes detailed demographic, clinical, behavioural and imaging information. DNA has been collected for genotyping from 5800 subjects. A component of the programme uses post-mortem tissue to determine the probabilistic distribution of microscopic cyto- and chemoarchitectural regions in the human brain. This, combined with macroscopic information about structure and function derived from subjects in vivo, provides the first large scale opportunity to gain meaningful insights into the concordance or discordance in micro- and macroscopic structure and function. The philosophy, strategy, algorithm development, data acquisition techniques and validation methods are described in this report along with database structures. Examples of results are described for the normal adult human brain as well as examples in patients with Alzheimer's disease and multiple sclerosis. The ability to quantify the variance of the human brain as a function of age in a large population of subjects for whom data is also available about their genetic composition and behaviour will allow for the first assessment of cerebral genotype-phenotype-behavioural correlations in humans to take place in a population this large. This approach and its application should provide new insights and opportunities for investigators interested in basic neuroscience, clinical diagnostics and the evaluation of neuropsychiatric disorders in patients.

Adult↗

PubMed2001

Hemispheric shape of European and Japanese brains: 3-D MRI analysis of intersubject variability, ethnical, and gender differences.

Hemispheric shape is studied using magnetic resonance imaging and 3-D reconstructions in right-handed, male and female, European and Japanese subjects. Japanese hemispheres are relatively shorter, but wider than European hemispheres. Regions of maximal intersubject variability in hemispheric shape are present in the occipital and temporal lobes in each sample. Deviations from this general pattern are found in the (i) right inferior parietal lobule (European hemispheres are more variable than Japanese), (ii) lower third of the pre- and postcentral gyri (female Japanese hemispheres are less variable than the other samples), (iii) right inferior frontal gyrus (male European hemispheres are more variable than the other samples), and (iv) polar part of the frontal lobe (female European hemispheres are less variable than the other samples). The distribution of intersubject variability between the hemispheres is less asymmetric in female than male brains. Male Japanese hemispheres are shorter but wider than female Japanese hemispheres, whereas European hemispheres show the inverse gender relations. These results demonstrate that hemispheric shape shows a considerable intersubject variability, which is not randomly distributed over the cortical surface but displays distinct regions of higher variability. Despite this intersubject variability significant interethnic- and gender-related differences in hemispheric shape are present, which may be relevant if individual brains have to be warped to a single or mean reference brain or realistic brain models are to be constructed.

Adult↗

PubMed2001

Activation reduction in anterior temporal cortices during repeated recognition of faces of personal acquaintances.

Repeated recognition of the face of a familiar individual is known to show semantic repetition priming effect. In this study, normal subjects were repeatedly presented faces of their colleagues, and the effect of repetition on the regional cerebral blood flow change was measured using positron emission tomography. They repeated a set of three tasks: the familiar-face detection (F) task, the facial direction discrimination (D) task, and the perceptual control (C) task. During five repetitions of the F task, familiar faces were presented six times from different views in a pseudorandom order. Activation reduction through the repetition of the F tasks was observed in the bilateral anterior (anterolateral to the polar region) temporal cortices which are suggested to be involved in the access to the long-term memory concerning people. The bilateral amygdala, the hypothalamus, and the medial frontal cortices, were constantly activated during the F tasks, and considered to be associated with the behavioral significance of the presented familiar faces. Constant activation was also observed in the bilateral occipitotemporal regions and fusiform gyri and the right medial temporal regions during perception of the faces, and in the left medial temporal regions during the facial familiarity detection task, which are consistent with the results of previous functional brain imaging studies. The results have provided further information about the functional segregation of the anterior temporal regions in face recognition and long-term memory.

Adult↗

PubMed2001

Different distribution of the activated areas in the dorsal premotor cortex during visual and auditory reaction-time tasks.

Sensorimotor association is an essential aspect of behavior. The dorsal part of the premotor cortex (PMd) is known to have an important role in sensorimotor association. Although it is suggested that the partially segregated groups of neurons are involved in sensorimotor association in different sensory modalities, it is not yet clear whether these groups occupy the PMd to the same or different extent. Therefore, we performed a functional magnetic resonance imaging study to compare activated regions in the PMd during simple reaction-time tasks with visual and auditory cues. Eight normal volunteers performed two simple reaction time tasks with a conventional on-off design; one is with a visual cue and the other is with an auditory cue. In both tasks, two regions in the left primary motor area (M1) (4a and 4p) and the bilateral PMd were activated. The two activated regions in the left M1 occupied the same areas in both the visual and the auditory tasks. However, in the PMd, the activated regions were situate medially during the visual task and laterally during the auditory task, along the precentral sulci. There was no overlap of significantly activated regions between two tasks, and areas specifically activated during the visual task were observed in the middle of the precentral sulci, bilaterally. The results suggest that the distribution of PMd subregions involved in sensorimotor association differ when the sensory cues are in different modalities.

Adult↗

PubMed2001

Activation in the ipsilateral posterior parietal cortex during tool use: a PET study.

The basis of perceptual assimilation of tool and hand has been considered to be in modification of body schemata, for which integration of multimodal sensory information about our body parts is required. Using positron emission tomography and H(2)(15)O, we aimed to identify brain regions that change their neural activity in association with changes in neural processing of visual and/or somatosensory information when humans use a simple tool. Normal subjects were instructed to manipulate a small graspable object with a pair of tongs or with the fingers of their right or left hand. The only site activated during manipulation with the tool, compared with the fingers, with the right hand was the lateral edge of the right intraparietal sulcus (IPS). During manipulation using the left hand with the tool, compared with using the fingers, an area in the middle part of the left IPS was activated. Areas in the contralateral hemisphere were activated during both the tool-use and the finger-use tasks compared to the control task, but there was no statistically significant difference between the tool-use and the finger-use tasks. Therefore, the results suggest that the ipsilateral posterior parietal cortex was recruited during the tool-use tasks to integrate visuosomatosensory information.

Adult↗

PubMed2001

Neural substrates for recognition of familiar voices: a PET study.

Identification of familiar people is essential in our social life. We can identify familiar people by hearing their voices as well as by viewing their faces. By measuring regional cerebral blood flow (rCBF) by positron emission tomography (PET), we identified neural substrates for the recognition of familiar voices. The brain activity during discrimination of voices of the subjects' associates and friends from those of unfamiliar people was compared with that during an analogous discrimination of their own voice from unfamiliar voices as well as during vowel discrimination. The left frontal pole, right temporal pole, right entorhinal cortex, and left precuneus were activated to a greater extent during discrimination of familiar voice than during control discriminations, suggesting that these brain regions are involved in the recognition of familiar voices. Furthermore, the adjusted values of rCBF in the left frontal pole and right temporal pole correlated with the number of subjects' correct identification of familiar voices. The present results suggest that these two regions are coactively associated with matching the currently heard voice to familiar voices in one's memory.

Adult↗

PubMed2001

Different neural systems for recognizing plants, animals, and artifacts.

The purpose of this study was to investigate functional organization in the human brain involved in the representation of knowledge regarding plants. We measured the brain activity of eight male volunteers during the recognition of visual stimuli representing plants, animals and artifacts, using positron emission tomography. The participants were presented with and were required to name silently two different images each of 15 entities belonging to three ontological categories, and 30 series of four to six digits. Marked increases in regional cerebral blood flow were found in the hippocampus and the parahippocampal areas bilaterally and the right lateral occipital cortex during the silent naming of all three categories, compared with that during the silent reading of digits. The right lateral occipital cortex was specifically activated in association with the naming of plants, and the right fusiform cortex was specifically activated in association with the naming of animals. In addition, the right temporo-occipital cortex was activated only during animals and plants, not artifacts. Our results indicate that there were a few characteristic activations for the different categories, and that entities belonging to the different categories are not necessarily represented in different locations of the brain.

Cerebral Cortex↗

PubMed2001

Effect of naturally occurring E2F-4 alterations on transcriptional activation and proliferation in transfected cells.

E2F is a family of transcription factors implicated in the regulation of gene expression required for progression through the G(1)-S transition. We have previously detected tumor-specific mutations at a trinucleotide repeat coding sequence of E2F-4 gene in a subset of human sporadic colorectal cancers. The purpose of this study was to investigate the potential functional consequences of these E2F-4 mutations. We transfected NIH3T3 fibroblasts with expression constructs containing wild-type as well as mutant E2F-4 cDNA, and the effect of the E2F-4 mutations on proliferation was examined. Alteration in transactivation of the E2F consensus promoter sequence was also examined by transient cotransfection of a E2F-4 with a DP-2 construct into cultured human cells. Transfected cell clones overexpressing mutant E2F-4 grew more rapidly and showed higher proliferative activity by increased immunohistochemical staining for proliferating cell nuclear antigen (PCNA). All three mutant forms of E2F-4 showed elevated transactivation of the E2F consensus promoter sequence. Thus, expression of mutant E2F-4s confers a growth advantage in vivo, and this effect may be related to the acquisition of a neoplastic phenotype.

3T3 Cells↗

PubMed2001

Platelet-derived growth factor is involved in the augmentation of airway responsiveness through remodeling of airways in diesel exhaust particulate-treated mice.

BACKGROUND: Thickening of the region adjacent to the basement membrane is a key component of the remodeling of the asthmatic airway and is caused by collagen deposition in the region. OBJECTIVE: We sought to clarify the role of platelet-derived growth factor (PDGF), a competence factor of fibroblast, in the enhanced airway responsiveness and remodeling in a murine model. METHODS: Diesel exhaust particulates (DEPs) were administered intranasally every other day for 2 weeks with or without anti-PDGF-beta neutralizing antibody or goat IgG. Pulmonary function was then analyzed by using whole-body plethysmography before and after acetylcholine inhalation. RESULTS: Anti-PDGF-beta neutralizing antibody significantly inhibited both the elevation of airway resistance elicited by 1.25 and 2.5 mg/mL acetylcholine and the increase in the airway wall thickening induced by DEPs. In addition, bronchoalveolar lavage fluid cell analysis revealed that anti-PDGF-beta neutralizing antibody did not affect cellular infiltration at the airways. CONCLUSION: PDGF plays an important role in the process of remodeling brought about by DEP exposure in mice.

3T3 Cells↗

PubMed2001

[Functional imaging studies of attention].

Functional organization of the human brain involved in attention has been determined in many human brain imaging studies. Most of these studies focused on brain mechanism related to selective attention using different sensory modality or sub-modality stimuli. Recently, we have shown other aspects of human attentional system, that is spatial attention, using event-related functional MRI. In this study, using delayed sequential saccade paradigm, subjects were forced to pay their attention towards right or left visual field. We could not find significant difference in brain activation patterns between right and left visual field attention tasks. The results are inconsistent to the findings of the previous lesion studies of humans showing spatial neglect. Further collaborative studies of neurological and brain mapping researches should be necessary to understand human higher cognitive functions.

Attention↗

PubMed2000

Retention of words in long-term memory: a functional neuroanatomical study with PET.

We used PET to identify brain regions associated with retention of verbal materials in long-term memory. During a PET scan, subjects repeated many sets of words one after another. In a retention condition, they were simultaneously required to retain 10 key words that were irrelevant to the repetition task. Significant increases in regional cerebral blood flow during the retention condition were found in bilateral parahippocampal regions, the left prefrontal and parietal association cortices, the supplementary motor area, the neostriatum and the cerebellum. We clearly demonstrated that retention of verbal materials was accompanied by neural activities in the medial temporal lobes. We also showed that, in the early phase, retention of words in long-term memory recruited left cortical areas surrounding those relevant to verbal short-term memory.

Acoustic Stimulation↗

PubMed2000

Passive and active recognition of one's own face.

Facial identity recognition has been studied mainly with explicit discrimination requirement and faces of social figures in previous human brain imaging studies. We performed a PET activation study with normal volunteers in facial identity recognition tasks using the subject's own face as visual stimulus. Three tasks were designed so that the activation of the visual representation of the face and the effect of sustained attention to the representation could be separately examined: a control-face recognition task (C), a passive own-face recognition task (no explicit discrimination was required) (P), and an active own-face recognition task (explicit discrimination was required) (A). Increased skin conductance responses during recognition of own face were seen in both task P and task A, suggesting the occurrence of psychophysiological changes during recognition of one's own face. The left fusiform gyrus, the right supramarginal gyrus, the left putamen, and the right hypothalamus were activated in tasks P and A compared with task C. The left fusiform gyrus and the right supramarginal gyrus are considered to be involved in the representation of one's own face. The activation in the right supramarginal gyrus may be associated with the representation of one's own face as a part of one's own body. The prefrontal cortices, the right anterior cingulate, the right presupplementary motor area, and the left insula were specifically activated during task A compared with tasks C and P, indicating that these regions may be involved in the sustained attention to the representation of one's own face.

Adult↗