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Ryuta Kawashima

Publications and source records attributed to Ryuta Kawashima.

At least 37 records · Page 2Linked to original sources
PubMed2005

[Cognitive rehabilitation for Alzheimer disease--the learning therapy].

We propose a new intervention program, the concept of which is derived from the knowledge of both brain science and clinical studies. We set up a hypothesis that activation of the association cortices by cognitive tasks may well improve the function of these cortices. To choose effective cognitive tasks for activation of the association cortices, we reviewed previous neuroimaging studies. Then, we prepared two tasks in arithmetic and Japanese language, which were systematized basic problems in reading and arithmetic, for the training program. Sixteen experimental and 16 control subjects participated. The subjects of the experimental group were asked to perform a training program using learning tasks in reading and arithmetic. The function of the frontal cortex of the subjects was assessed by FAB (frontal assessment battery at bedside). After six months of training, the FAB score of the experimental group showed a statistically significant improvement. We also observed the restoration of communication and independence, and improvement in relationships with the clinical staff in the experimental group. Our results indicate that learning tasks of reading aloud and arithmetic calculation can be used for cognitive rehabilitation, which improves frontal functions, of dementia patients.

Aged↗
PubMed2005

[A new intervention program for improvement of cognitive functions of senile dementia patients].

We proposed a new intervention program, the concept of which is derived from the knowledge of both brain science and clinical studies. We set up a hypothesis that activation of the association cortices by cognitive tasks may well improve the function of these cortices. To choose effective cognitive tasks for activation of the association cortices, we reviewed previous neuroimaging studies. Then, we prepared two tasks in arithmetic and Japanese language, which were systematized basic problems in reading and arithmetic, for the training program. Sixteen experimental and 16 control subjects participated. The subjects of the experimental group were asked to perform a training program using learning tasks in reading and arithmetic. The function of the frontal cortex of the subjects was assessed by FAB (frontal assessment battery at bedside). After six months of training, the FAB score of the experimental group showed a statistically significant improvement. We also observed the restoration of communication and independence, and improvement in relationships with the clinical staff in the experimental group. Our results indicate that learning tasks of reading aloud and arithmetic calculation can be used for cognitive rehabilitation, which improves frontal functions of dementia patients.

Aged, 80 and over↗
PubMed2004

Role of the cerebellum in implicit motor skill learning: a PET study.

To depict neural substrates of implicit motor learning, regional cerebral blood flow was measured using positron emission tomography (PET) in 13 volunteers in the rest condition and during performance of a unimanual two-ball rotation task. Subjects rotated two balls in a single hand; a slow rotation (0.5 Hz) was followed by two sessions requiring as rapid rotation as possible. The process was repeated four times by a single hand (Block 1) and then by the opposite hand (Block 2). One group of volunteers began with the right hand (n = 7), and the other with the left (n = 6). Performance was assessed by both quickness and efficiency of movements. The former was assessed with the maximum number of rotation per unit time, and the latter with the electromyographic activity under constant speed of the movement. Both showed learning transfer from the right hand to the left hand. Activation of cerebrum and cerebellum varied according to hand. Activation common to both hands occurred in the bilateral dorsal premotor cortex and parasagittal cerebellum, right inferior frontal gyms, left lateral cerebellum and thalamus, supplementary motor area, and cerebellar vermis. The left lateral cerebellum showed the most prominent activation on the first trial of the novel task, and hence may be related the early phase of learning, or "what to do" learning. Left parasagittal cerebellum activity diminished with training both in first and second blocks, correlating inversely with task performance. This region may therefore be involved in later learning or "how to do" learning. The activity of these regions was less prominent with prior training than without it. Thus the left cerebellar hemisphere may be related to learning transfer across hands.

Adult↗
PubMed2004

Mental visual synthesis is originated in the fronto-temporal network of the left hemisphere.

Mental visual synthesis is the capacity for experiencing, constructing, or manipulating 'mental imagery'. To investigate brain networks involved in mental visual synthesis, brain activity was measured in right-handed healthy volunteers during mental imagery tasks, in which the subjects were instructed to imagine a novel object, that does not exist in the real world, by composing it from two visually presented words associated with a real object or two achromatic line drawings of a real object, using functional magnetic resonance imaging (fMRI). Both tasks activated the same areas in the inferior frontal and inferior temporal cortices of the left hemisphere. Our results indicate that the source of mental visual synthesis may be formed by activity of a brain network consisting of these areas, which are also involved in semantic operations and visual imagery.

Adolescent↗
PubMed2004

Different roles of the frontal and parietal regions in memory-guided saccade: a PCA approach on time course of BOLD signal changes.

Although involvement of the frontoparietal regions in visually guided saccade and visuospatial attention has been established, functional difference of the frontal and parietal regions suggested in neuropsychological observations and lesion studies in animals has not been explicitly supported by functional imaging studies. Considering a possible disadvantage of cognitive subtraction in an interregional comparison, we directly compared the time course of BOLD signal changes across regions. Normal subjects performed a modified version of a memory-guided saccade task in which saccade was performed both during encoding and execution phases. In addition, the delay period was fixed and the peripheral target was presented also during the execution phase together with distracters. Therefore, visuospatial representation was likely maintained in the sensory domain during the delay phase. A principal component analysis on the time-course data separated the 20 activated areas into three groups, which largely coincided with the cerebral lobes. The frontal group included the putative human FEF and SEF, and the parietal group PEF. The frontal and occipital groups exhibited the time course of activation with two peaks corresponding to neural responses during the encoding and execution phases, and the parietal group exhibited a single-humped activation pattern corresponding to neural activity during the delay phase. The results suggest that the frontal regions are more associated with the execution of saccade, and the parietal regions with visuospatial representation, presumably in the sensory domain.

Adolescent↗
PubMed2004

A functional MRI study of simple arithmetic--a comparison between children and adults.

The purpose of this study was to examine brain areas involved in simple arithmetic, and to compare these areas between adults and children. Eight children (four girls and four boys; age, 9-14 years) and eight adults (four women and four men; age, 40-49 years) were subjected to this study. Functional magnetic resonance imaging (fMRI) was performed during mental calculation of addition, subtraction, and multiplication of single digits. In each group, the left middle frontal, bilateral inferior temporal and bilateral lateral occipital cortices were activated during each task. The adult group showed activation of the right frontal cortex during addition and multiplication tasks, but the children group did not. Activation of the intraparietal cortex was observed in the adult group during each task. Although, activation patterns were slightly different among tasks, as well as between groups, only a small number of areas showed statistically significant differences. The results indicate that cortical networks involved in simple arithmetic are similar among arithmetic operations, and may not show significant changes in the structure during the second decade of life.

Adolescent↗
PubMed2004

Voxel-based morphometry of human brain with age and cerebrovascular risk factors.

The objectives of this study were to evaluate the correlations of the volumes of the gray matter and white matter with age, and the correlations of the tissue probabilities of the gray matter and white matter with age and several cerebrovascular risk factors. We obtained magnetic resonance (MR) images of the brain and clinical information from 769 normal Japanese subjects. We processed the MR images automatically by correcting for inter-individual differences in brain size and shape, and by segmenting the MR images into the gray matter and white matter. Volumetry of the brain revealed a significant negative correlation between the gray matter volume and age, which was not observed between white matter volume and age. Voxel-based morphometry showed that age, systolic blood pressure, and alcohol drinking correlated with the regional tissue probabilities of the gray matter and white matter.

Adolescent↗
PubMed2004

A state-space model of the hemodynamic approach: nonlinear filtering of BOLD signals.

In this paper, a new procedure is presented which allows the estimation of the states and parameters of the hemodynamic approach from blood oxygenation level dependent (BOLD) responses. The proposed method constitutes an alternative to the recently proposed Friston [Neuroimage 16 (2002) 513] method and has some advantages over it. The procedure is based on recent groundbreaking time series analysis techniques that have been, in this case, adopted to characterize hemodynamic responses in functional magnetic resonance imaging (fMRI). This work represents a fundamental improvement over existing approaches to system identification using nonlinear hemodynamic models and is important for three reasons. First, our model includes physiological noise. Previous models have been based upon ordinary differential equations that only allow for noise or error to enter at the level of observation. Secondly, by using the innovation method and the local linearization filter, not only the parameters, but also the underlying states of the system generating responses can be estimated. These states can include things like a flow-inducing signal triggered by neuronal activation, de-oxyhemoglobine, cerebral blood flow and volume. Finally, radial basis functions have been introduced as a parametric model to represent arbitrary temporal input sequences in the hemodynamic approach, which could be essential to understanding those brain areas indirectly related to the stimulus. Hence, thirdly, by inferring about the radial basis parameters, we are able to perform a blind deconvolution, which permits both the reconstruction of the dynamics of the most likely hemodynamic states and also, to implicitly reconstruct the underlying synaptic dynamics, induced experimentally, which caused these states variations. From this study, we conclude that in spite of the utility of the standard discrete convolution approach used in statistical parametric maps (SPM), nonlinear BOLD phenomena and unspecific input temporal sequences must be included in the fMRI analysis.

Adult↗
PubMed2004

The human parietal cortex is involved in spatial processing of tongue movement-an fMRI study.

The human tongue is so sensitive and dexterous that spatial representations of the inside of the oral cavity for the tongue movement are naturally expected to exist. In the present study, we examined the brain activity associated with spatial processing during tongue movements using a functional magnetic resonance imaging technique. Twenty-four normal subjects participated in the study, which consisted of a periodic series of three blocks; resting of the tongue, tongue movement (pressing the inside of a tooth with the tip of the tongue), and tongue retraction. The cerebral fields of activation during the tongue movement to the left and right side relative to those during rest were found in the primary sensorimotor area and supplementary motor area bilaterally, and in the left inferior parietal lobule (IPL). The activation areas during the tongue retraction relative to those during rest were almost the same, except that activation in the left IPL was not observed. The fields of activation during tongue movement to the left and right side relative to those during tongue retraction were found bilaterally in the dorsal premotor area, superior parietal lobule (SPL), and the IPL. The results indicate that the bilateral SPL and IPL were specifically involved in the processing for human tongue movement. Although no significant laterality was observed, the left parietal area tended to show greater activation in statistical values and area than the right parietal area, thus indicating the possibility that this processing for human tongue movement is related to that for language.

Adult↗
PubMed2004

Target dependency of brain mechanism involved in dispositional inference: a PET study.

The cognitive mechanism for inference of personal dispositions, such as personality traits and abilities, is postulated to be dependent on the amount of episodic memory concerning target persons. To examine whether there is such target dependency in the brain mechanism during dispositional inference, we measured brain activity of normal volunteers while they were performing seven dispositional inference tasks, each for a target person in different categories, using positron emission tomography (PET). Effect of the target-person category on activation was significant in the posterodorsal, polar, and ventral subdivisions of medial prefrontal cortex, right orbitoinsular junction, left temporal pole and superior temporal sulcus, cerebellum, and thalamus, suggesting the existence of target dependency in activation during dispositional inference. The amount of episodic memory concerning a target person measured using the self-evaluative questionnaire was positively correlated with the activation in the polar subdivision of the medial prefrontal cortex, and negatively with that in a region in the left superior temporal sulcus. Together with the available knowledge on the functional roles of these regions and the proposed cognitive model in social psychology, our results suggest that these two regions play roles supplementary to each other in dispositional inference; a region in the superior temporal sulcus is involved in the processing of relevant episodic exemplar and the polar subdivision of the medial prefrontal cortex in the processing of summarized value information about the target person.

Adolescent↗
PubMed2003

Cortical activation during reading aloud of long sentences: fMRI study.

The purpose of this study was to investigate human brain activity during the reading aloud of Japanese sentences using fMRI. Twenty-three right-handed normal Japanese subjects performed three reading tasks: covert reading of meaningful or meaningless sentences, and reading aloud of meaningful sentences. Areas in the bilateral frontal and temporal cortices were activated during the reading-aloud task compared with the covert reading task. In addition, activation of these brain areas showed significant positive correlation with the reading speed during the reading-aloud task. Our results indicate that bilateral frontal-temporal networks are involved in phonological processing during reading aloud.

Adolescent↗
PubMed2003

Can personality traits predict pathological responses to audiovisual stimulation?

The "Pockemon shock" is the most famous accident in the history of the broadcasting industry in Japan. Based on the experiences of this unfortunate accident from famous animation program "Pocket Monster", this study focused on the psychology and psychosomatics of the patients. A head-mounted display was used as the three-dimensional image presentation device and "Descent", a free software shooting game, was used as the software. Ten healthy adult male volunteers were used in this experiment after obtaining their informed consent. The oxygen metabolic change in the anterior lobe of the brain was measured by near infrared spectroscopy and recorded on an electrocardiogram. The mental scaling tendency of the object was analyzed using the type A behavior pattern and the hostility scaling. The Cook and Medley hostility (HO) scale from the Minnesota multiphasic personality inventory (MMPI) was also used in this experiment. From this scaling methodology, the paranoid scale, cynicism scale, lie scale, social support quality and social support quantity were calculated. All measured time series data were kept in the normal range, and no fatal arrhythmia or epilepsy were observed during experiments. In some cases, the brain oxygen metabolism may completely differ for the objects of Type A and Type B behavior patterns. On the whole, correlation did not become significant in type A scaling and hostility scaling. In a comparison of the percent changes of the HF in HRV with lie scaling, significant negative correlation was observed. The social support quantity was calculated from Cook and Medley, and significant negative correlations were observed with percent changes of LF/HF in HRV. The lie scale and social support quantity are opposite scaling. The sympathetic nervous system and parasympathetic nervous system have an opposite function also. Therefore, our results showed an interesting phenomenon, when considering the relationship between the autonomic function and the pathophysiological reaction to the audiovisual stimulations. As for the photo sensitive epilepsy, it was reported to be only 5-10% for all patients. Therefore, 90% or more of the cause could not be determined in patients who started a morbid response. The results in this study suggest that the autonomic function was connected to the mental tendency of the objects. By examining such directivity, it is expected that subjects, which show morbid reaction to an audiovisual stimulation, can be screened beforehand.

Acoustic Stimulation↗
PubMed2003

Neuroanatomical database of normal Japanese brains.

To develop a high-resolution in vivo human neuroanatomy database for Japanese brains, a data set on 1547 normal subjects between the ages of 16 and 79 years has been collected. First, we determined individual reference brains of normal Japanese for each age and gender group. We found there exists cross-generational changes in brain shape, that is, the young generation has a shorter and wider brain than the older generation. Second, we determined the effect of aging on the volume of gray matter and white matter by voxel based morphometry. A significant negative correlation between the gray matter volume and age was observed. We assume that this kind of database is quite useful to investigators who are engaged in basic neuroscience, clinical diagnostics and evaluation of neuropsychiatric disorders in patients.

Adolescent↗
PubMed2003

Thinking of the future and past: the roles of the frontal pole and the medial temporal lobes.

Human lesion data have indicated that the frontal polar area might be critically involved in having an insight into one's future. Retrospective memory mediated by medial temporal lobes and related structures, on the other hand, could be used to extract one's future prospects efficiently. In the present study, we investigated the roles of these two brain structures in thinking of the future and past by using positron emission tomography (PET) and a naturalistic task setting. We measured regional cerebral blood flow (rCBF) in healthy subjects while they were talking about their future prospects or past experiences, with regard to two different temporal windows (in years or days). Many areas in the frontal and the medial temporal lobes were activated during the future and past tasks compared with a control task requiring semantic retrieval. Among these, areas in anteromedial frontal pole showed greater activation during the future tasks than during the past tasks, showing significant effect of temporal distance from the present. Most areas in the medial temporal lobes showed greater or equivalent level of activations during the future tasks compared with the past tasks. The present results suggest that thinking of the future is closely related to retrospective memory, but that specific areas in the frontal pole and the medial temporal lobes are more involved with thinking of the future than that of the past.

Adult↗
PubMed2003

Context-dependent cortical activation in response to financial reward and penalty: an event-related fMRI study.

An event-related fMRI technique was used to assess neural responses to financial reward and penalty during a simple gambling task. We attempted to determine whether brain activities are dependent on the unique context of an event sequence. Thirty-six healthy volunteers participated in the study. The task was to guess the color of the suit of a card on each trial and to respond by pressing a button. Every correct response ("win") and incorrect response ("loss") was associated with financial reward and penalty, respectively. The magnitude of reward or penalty in each trial did not change; however, the subjects' self-reported emotional arousal was significantly higher for the events of "the fourth win of four wins in a row" and "the fourth loss of four losses in a row." We also found that the bilateral anterior cingulate and medial prefrontal cortices were specifically activated when the subjects experienced "the fourth win of four wins in a row" and "the fourth loss of four losses in a row." When the subjects experienced "a win following four losses in a row" or "a loss following four wins in a row," the right dorsolateral prefrontal cortex was specifically activated. Our data indicate that there exist brain activities associated with the event-sequence context in which abstract reward or penalty is received. These context-dependent activities appear to be crucial for adapting oneself to new circumstances and may account for clinical symptoms of various mental illnesses in which dysfunction of these regions has been reported.

Adolescent↗
PubMed2002

Time-dependent contribution of the hippocampal complex when remembering the past: a PET study.

Previous studies of brain-damaged patients and functional neuro-imaging have consistently shown the importance of the hippocampal complex, i.e. the hippocampus and parahippocampal gyrus, in episodic memory retrieval. We wished to determine whether patterns of brain activation during memory retrieval as measured by PET are same or different when the oldness of a to-be-retrieved episode is manipulated. Using cue words, subjects remembered related episodes from three periods of their life, childhood, adolescence and recent period. The results showed an increase of parahippocampal activities during recall of episodes from childhood and recent period, but not from adolescence. These data suggest a possibility of time-dependent hippocampal contribution in episodic recall, which cannot be understood in simple terms of recent remote memory dichotomy.

Adolescent↗
PubMed2002

Neural basis of the retrieval of people's names: evidence from brain-damaged patients and fMRI.

The aim of this study was to identify the neuroanatomical basis of the retrieval of people's names. Lesion data showed that patients with language-dominant temporal lobectomy had impairments in their ability to retrieve familiar and newly learned people's names, whereas patients with language-nondominant temporal lobectomy had difficulty retrieving newly learned people's names. Functional magnetic resonance imaging experiments revealed activations in the left temporal polar region during the retrieval of familiar and newly learned people's names, and in the right superior temporal and bilateral prefrontal cortices during the retrieval of newly learned information from face cues. These data provide new evidence that the left anterior temporal region is crucial for the retrieval of people's names irrespective of their familiarity and that the right superior temporal and bilateral prefrontal areas are crucial for the process of associating newly learned people's faces and names.

Adolescent↗