- 2005 Conference Abstracts
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- 松澤正子
- Temporal relationship between action and visual outcome modulates brain activation: An fMRI study
- Monitoring visual outcomes of our actions is critical component of our visuo-motor behavior. To investigate the neural basis of the monitoring system in looking at a visual change produced by a self-movement, the effect of the temporal relationship between a manual button press and visual feedback on brain activation was examined. Six neurologically normal subjects participated in three experiments. Their brain images during the experiments were acquired using an MRI scanner operating at 3 Tesla. In the Synchronous experiment, subjects pressed a button at self-paced intervals, and were presented visual stimuli synchronously with the button press. In the Delayed experiment, visual stimuli were presented with a delay after subjects pressed a button at self-paced intervals. In a control experiment (Visual experiment), subjects did not press the button, but viewed visual stimuli generated by a computer at random intervals. Activation in the cerebellum and right parietal lobe was stronger in the Synchronous experiment than in the Delayed experiment, while activation in the primary visual cortex was attenuated in the Synchronous experiment as compared to the Delayed experiment and Visual experiment. These results suggest that visual outcomes produced synchronously with action are processed in the cerebellum and the parietal area for organizing optimal motor behavior, rather than in the primary visual area that is known to process visual properties of external objects. The cerebellar signal related to visuo-motor contingency might modulate the cortical processing of visual inputs that are synchronous with action.
- 中井敏晴
- An fMRI study to investigate auditory attention: A model of the cocktail party phenomenon
- In the human life, discrimination of the target voice from other voices or sounds is indispensable, and its disturbance results as sensory aphasia. In order to investigate the neuronal basis of the attentional system for human voices, the brain activity during listening comprehension task was evaluated using functional magnetic resonance imaging (fMRI) at 3T. Diotic listening comprehension tasks, in which a narration was superimposed by another given by the same speaker (SV experiment) or by a different speaker (DV experiment), were presented to normal volunteers. The story indicated in the baseline task blocks, in which only one narration was presented, was intensively followed during the superimposed task blocks. In each experiment, six task blocks, 3 blocks for each condition, and 7 rest blocks were alternatively repeated, and the contrast of the superimposed condition to the baseline condition in each session was obtained. In the DV experiment, the activation in Wernicke's area (BA22) was increased compared with the control condition. In the SV experiment, activation in the frontal association cortex (BA6, BA9/46, BA32, BA13/47) was additionally increased. These results suggested that difficulty in phonological processing to discriminate human voices calls for further semantic, syntactic and prosodic processing, as well as augmented selective attention.
- 斎藤もよこ
- An investigation of pipeline materials for continuous hyperpolarized 129Xe gas spectroscopy
- In order to establish a continuous hyperpolarized xenon-129 (HP-129Xe) gas delivery system for MR imaging, the effect of the metallic materials in the gas pipeline on the signal intensity was investigated. In the gas pipeline, an appropriate surface is needed to minimize wall relaxation by the HP-129Xe gas caused by the interaction between the HP gas and the surface, which can lead to signal loss. Although Pyrex glass is a popular material for the HP gas chamber, it is fragile under heat or physical stress. In this study, five stainless steel tubes (STs) prepared with different surface film-forming processes were examined. The MR signal intensities of HP-129Xe gas that passed through each tube were then compared. The film passivated by iron fluoride maintained the highest level of hyperpolarization, whereas that passivated by chromium oxide maintained the lowest. A ST with an appropriate passive film may be a useful alternative to a Pyrex glass pipeline.
- 大石健一
- Activation of the precuneus is related to reduction time in serial reaction time tasks
- Multiple brain areas are activated during serial reaction time (RT) tasks (SRTTs), but the part of the brain that facilitates reductions in RT remains unclear. The present study attempted to determine the brain region contributing most to speed-up of RT during an explicit SRTT. Eighteen healthy subjects participated in the functional magnetic resonance imaging study using a 3-T scanner. Subjects were instructed to press one of four buttons corresponding to visual stimulus as quickly as possible and with minimal errors during the scan session. Stimuli were presented either in random order (control condition) or in a repeated 6-item sequence (learning condition). To clarify the explicit mechanisms of sequence learning, subjects were informed of the existence of a repeating 6-item sequence in the learning condition. Conventional analysis contrasting learning and control conditions revealed widely distributed activation predominantly in the fronto-parietal network. Consistent with previous studies, frontal activation preceded parietal activation, indicating that specific sets of brain areas were activated in each step of the learning process. Correlations between change in RT (.RT) and brain activation were then analyzed, and .RT was found to correlate only with precuneus activation. The precuneus is known to play critical roles in the retrieval of stored memory and execution of limb movements. Reductions in RT during the SRTT were related to activation in the precuneus, which may offer a good indicator for retrieval and execution functions.
- エピファニオ・バガリナオ
- Enabling real-time functional MRI analysis using computational grids
- The analysis of brain imaging data such as functional MRI often requires considerable computing resources, which in most cases are not readily available in many medical imaging facilities. This lack of computing power makes it difficult for researchers and medical practitioners alike to perform on-site analysis of the generated data. Given the cost of imaging experiment time, it is disappointing for the researcher and/or the subject to complete an examination only to find out later that the results are inadequate due to errors encountered during data gathering. This paper presents a system that is capable of analyzing functional MRI data in real time with results available within seconds after data acquisition. The system employs remote computational servers to provide the necessary computing power. System integration is accomplished by an accompanying software package, which includes fMRI analysis tools, data transfer routines, and easy-to-use graphical user interface. The remote analysis is transparent to the user as if all computations are performed locally. Simulation runs achieved fully real-time performance with a total processing time of 1.089 s per image volume (64 x 64 x 30 in size), much less than the per volume acquisition time set to 3.0 s.
- 中井敏晴
- An fMRI study of temporal sequencing of motor regulation guided by an auditory cue-a comparison with visual guidance
- The neuronal basis of the higher motor regulation driven by an auditory cue was investigated using fMRI. For the constant movement conditions, volunteers performed a finger opposition movement at 0.5, 1 or 2Hz according to a 1Hz monotone cue. For the intermittent conditions, a 2Hz movement was performed every other second according to the 1Hz monotone cue or dot prompting. The activity in the network of the supplementary motor area, premotor area, superior parietal lobule and cerebellum responded to the demand for the complexity of the movement. Since this observation agreed with a previous study that used the same finger movement guided by a visual cue, this network seems to be a common pathway across the modalities. The bilateral anterior portion of the BA22 (ant-BA22) and the left BA41/42 were more extensively activated by the intermittent movement under the auditory cue than that under the visual cue. However, among the four auditory conditions, the activation in the ant-BA22 was augmented only on the left side by the intermittent movement. The left ant-BA22 may be especially involved in integrating the external auditory cue with internal initiation, while the activation on the right side did not depend on the complexity. The role of the left BA41/42 in motor regulation may be more specific to the processing of an auditory cue, and different from that on the right side. These two areas in the left temporal lobe may be organized as a subsystem to handle the timing of complex movements under auditory cues.
- 斎藤もよこ
- Assesment of the specific absorption rate effects and decoupling calibration for proton decoupled carbon-13 MRS at 3.0T
- A strategy for proton decoupled carbon-13 MR spectroscopy ({1H}-13C MRS) with a strong static magnetic field (3T) in vivo was investigated. The proton decoupling improves the signal-to-nose ratio, however, the effect of the decoupling power on the human body, especially in strong magnetic fields, should be considered. In order to establish a technique for monitoring the metabolism glucose in the liver using {1H}-13C MRS at 3.0 T, two phantom experiments were performed. To assess whether the decoupling energy conformed to SAR limits defined by the IEC, temperature rises inside an agar phantom gel were monitored during a {1H}-13C MRS experiment. Then the decoupling conditions of a glucose solution phantom were optimized with various combinations of bandwidth and power. The reliability of this procedure was discussed based on these results in conjunction with IEC guidelines.