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- 2002 Conference Abstracts
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- 住吉チカ
- Orthography effect on brain activities ni the working memory process for phonologically ambiguous syllables: a functional magnetic resonance imaging study using japanese speakers
- English /l/ and /r/ sounds are not distinctive for Japanese speakers and they are loosely associated with corresponding graphemes. The purpose of this study was to investigate the brain activities in the memory process for the graphemes containing ‘l’ and ‘r’ in Japanese speakers. Two functional magnetic resonance imaging (at 1.5T) experiments was conducted using syllable working memory tasks. The task using ‘l’ and ‘r’ syllables was coupled with either task using‘b’ and ‘n’ syllables (l/r versus b/n block-designed experiment), or ‘d’ and ‘n’ syllables (l/r versus d/n block-designed experiment). The results revealed that the l/r working memory tasks induced augmented activation specifically in the right middle frontal gyrus (BA9, 46) and the right superior parietal lobule (BA7), compared with the b/n or d/n tasks. The results indicate that a visually-biased memory process (i.e. excessive visual rehearsal or monitoring) was executed for phonologically ambiguous syllables. Significant activation in the left inferior frontal gyrus was not observed only in the b/n task, probably because articulatory contrast between /b/ and /n/ sounds was highly clear for Japanese speakers.
- 當間圭一郎
- Functional MRI in human motor control studies and clinical application (review)
- Functional magnetic resonance imaging (fMRI) has been used as a useful tool for noninvasively mapping brain function associated with various motor and cognitive tasks. Since fMRI is based on blood-oxygenation level dependent effect, it does not directly record neural activities. Two major experimental designs are used in fMRI studies: block and even-related designs. Block-designed fMRI presupposes steady-state of regional cerebral blood flow and has been applied to examination of brain activation associated with sustained or repetitive movement task. By contrast, more recently developed event-related fMRI with time resolution of a few seconds allows for brain mapping caused by a single movement, based on transient aspects of hemodynamic response. In order to understand functional brain map, it is important to understand sequential and parallel organizations in anatomical connections of multiple motor areas. Increasing evidence has suggested that multiple motor areas are engaged in network manner to execute various motor acts. In fMRI studies on complex motor tasks, elementary parameters such as movement rate, magnitude and force should be controlled, because inconsistency of those parameters may alter the extent and intensity of motor cortical activation, confounding interpretation of obtained findings. In addition to initiation and maintenance of movements, termination of movements also plays important roles to successfully achieve complex movements. Brain areas selectively related to the termination of movements is, for the first time, uncovered by using event-related fMRI technique. We propose the application of the event-related fMRI to elucidate pathophysiology of movement disorders, in particular dystonia that exhibits involuntary co-contraction of agonist and antagonist muscles and manifests abnormalposture or slow repetition of movements.
- 中井敏晴
- Advantages of fMRI at ultra high magnetic field (review)
- The following is a review of the advantages of functional magnetic resonance imaging (fMRI) at ultra high field. A decade has passed since the primary development of BOLD contrast. A dramatic increase in the use of fMRI has produced numeroscience as well as cognitive science. MR imaging at ultra high field has played an essential role in the development of fMRI because it aloow for the extraction of higher motor and cognitive functions as a functional network.
- The main properties of ultra high field are better signal to noise ratio, longer T1 and higher resolution in chemical shift. Both the enhanced susceptibility effect and increased signal synergistically produce better signal to noise radio of the BOLD signal. Due to this ,BOLD contrast increases more than linearly according to the static magnetic field strength. In addition to this,signals originating from capillaries are more represented in BOLD signal accoeding to the field strength.This means that measurements at ultra high field allows for more reliable activities.
- To establish measurements at ultra high field, many technical developments have been made. These developments are pulse sequence optimization,high order shim system for a whole body magnet,field map correction,navigator echo phase correction,and resonator coils for transmitting, and receiving signals. These developments have compensated for the problems of motion artifact,physiological noise,and geometric distortion.
- Ultra high field of 3 to 4T has been applied to fMRI since the beginning of its use. Comparative fMRI studies between high field and ultra high field have shown a better detectability and specificity of measurements at ultra high field. Now ultra high field of 7 to 8T, is being tried and several preliminary studies have been reported.
- 松尾香弥子
- Manipulo-spatial processing of ideographic characters in left-handers: observation in fMRI
- It has been suggested that left-handers have a cerebral ambilaterality for language representation. Specifically, the use of the right hand for writing may have a specific effect on the cerebral organization in left-handers. In an investigation of the relationship between motor and visual language procedures, functional magnetic resonance imaging at three tesla was conducted during stroke counting of kanji (Japanese ideographic characters) in six left-handers who usually write with their right hand. Two types of stimulus presentation, phonography-displayed and kanji-displayed, were employed to examine the different neural pathways used for processing kanji. Each stimulus presentation involved two motor conditions: one allowed finger movements for tracing the characters, while the other disallowed finger movements. The tasks induced activation in the primary motor area the premotor area, the supplementary motor area, and the anterior cingulated gyrus as well as the parietal and occipital lobes (Brodmann's area 7/39/19). The activated areas in both the movement-allowed and movement-disallowed conditions were almost identical except for the primary motor area. These results clearly contrasted with those of a previous study of right-handers which showed that right-handed volunteers demonstrated decreased activation in the premotor area and the dorsal pathway during the movement-allowed condition. This discrepancy may be attributable to a difference in cerebral organization for language processing. Specifically, in left-handers, the visuospatial procedure for kanji and the motor procedure for tracing the kanji may be ambilaterally distributed in both hemispheres, whereas in right-handers these procedures may be predominantly lateralized in the left hemisphere.