Biomedical subjects

Kayako Matsuo

Publications and source records attributed to Kayako Matsuo.

15 recordsLinked to original sources

PubMed2006

Dynamic monitoring of brain activation under visual stimulation using fMRI--the advantage of real-time fMRI with sliding window GLM analysis.

An fMRI technique based on real-time analysis was applied to evaluate the advantages of dynamic monitoring of the t-statistics based on a general linear model. The temporal change of the t-statistics in V1 and V4 under four conditions of visual stimuli covering different visual fields with or without coloring was estimated using an incremental analysis and a sliding window analysis (SWA). The SWA not only visualized the dynamic change of the activation in response to the task conditions and switching, but also enabled us to evaluate the temporal correlation of the t-statistics among the four visual areas. It was suggested that the activity in the V4 was bilaterally organized, and the altering color stimuli gave stronger stimulation to the V1 than did the black and white stimuli. Although the activation map at each time point represents the brain activity during several task and rest blocks, a SWA will be useful to evaluate the transition of neuronal activation in response to several sequential task conditions. An incremental analysis will be useful to monitor the ongoing activation in real-time during the scan, since it gives a higher t-value according to the accumulation of volume data. These two methods will be complementary.

Adult↗

PubMed2005

Activation of the precuneus is related to reduced reaction 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 improved RTs during explicit SRTTs. Subjects comprised 18 healthy volunteers who were instructed to press one of four buttons corresponding to visual stimuli as quickly as possible and with minimal errors during functional MRI. Stimuli were presented either in random order (control condition) or in a repeated six-item sequence (learning condition). Conventional analysis contrasting learning and control conditions revealed activation in the prefrontal-parietal area, which shifted to motor area. Subjects with high RT reduction showed more prominent activation in the precuneus than subjects with low RT reduction. Intra-subject correlation analysis revealed that time course of precuneus activation was unrelated to time-course of RT reduction. However, inter-subject correlation analysis revealed that RT changes correlate only with precuneus activation, meaning that subjects showing more prominent RT reduction revealed more prominent activation of the precuneus, which is known to play critical roles in controlling finger movements with reference to buffered memory.

Adult↗

PubMed2005

Temporal relationship between action and visual outcome modulates brain activation: an fMRI study.

Monitoring the visual outcome of our actions is critical to our visuo-motor behavior. To investigate the neural basis of monitoring visual change produced by self-movement, we examined the temporal relationship between manual depression of a button and visual feedback on activation of the brain. Six neurologically normal subjects participated in 3 experiments (synchronous, delayed, and visual [control]). Magnetic resonance (MR) images of their brains were acquired during the experiments using a scanner operating at 3T. In the synchronous experiment, subjects pressed a button at self-paced intervals and received synchronous visual stimuli in response. In the delayed experiment, visual stimuli were presented with a delay after subjects pressed a button at self-paced intervals. In the control experiment (visual experiment), subjects did not press the button, but viewed visual stimuli generated by a computer at random intervals. In the synchronous experiment, activation in the cerebellum and right parietal lobe was stronger than in the delayed experiment, whereas activation in the primary visual cortex was weaker than in the delayed and visual experiments. These results suggest that visual outcomes produced synchronously with action are processed in the cerebellum and the parietal area for the organization of optimal motor behavior, rather than in the primary visual area that is known to process the visual properties of external objects. The cerebellar signal related to visuo-motor contingency may modulate the cortical processing of visual input that is synchronous with action.

Adult↗

PubMed2005

An FMRI study to investigate auditory attention: a model of the cocktail party phenomenon.

In human life, discrimination of a target voice from other voices or sounds is indispensable, and inability for such discrimination results in sensory aphasia. To investigate the neuronal basis of the attentional system for human voices, we evaluated brain activity during listening comprehension tasks 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, 6 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, compared with the control condition, activation in Wernicke's area (BA22) was increased. 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.

Acoustic Stimulation↗

PubMed2004

An fMRI study of tool-use gestures: body part as object and pantomime.

A body part as object (BPO) gesture is one of the error patterns in apraxia. In the BPO gesture, people represent objects by their hands. To clarify the neuronal background of the BPO gesture, we compared the brain activation during the BPO gesture with that during ordinary pantomime in normal subjects using functional magnetic resonance imaging. Both the BPO gesture and the pantomime induced activation in the left parietal areas (Brodmann's area (BA) 7, 40), irrespective of the hand used. These areas might be activated by a common process of tool-related gestures. The BPO gesture also activated the right supramarginal gyrus (BA 40). This activation might reflect the characteristic process of BPO, the correlation of hands with tools by their forms and movements.

Adult↗

PubMed2004

Application of independent component analysis to magnetic resonance imaging for enhancing the contrast of gray and white matter.

An application of independent component analysis (ICA) was attempted to develop a method of processing magnetic resonance (MR) images to extract physiologically independent components representing tissue relaxation times and achieve improved visualization of normal and pathologic structures. Anatomical T1-weighted, T2-weighted and proton density images were obtained from 10 normal subjects, 3 patients with brain tumors and 1 patient with multiple sclerosis. The data sets were analyzed using ICA based on the learning rule of Bell and Sejnowski after prewhitening operations. The three independent components obtained from the three original data sets corresponded to (1) short T1 components representing myelin of white matter and lipids, (2) relatively short T1 components representing gray matter and (3) long T2 components representing free water. The involvement of gray or white matter in brain tumor cases and the demyelination in the case of multiple sclerosis were enhanced and visualized in independent component images. ICA can potentially achieve separation of tissues with different relaxation characteristics and generate new contrast images of gray and white matter. With the proper choice of contrast for the original images, ICA may be useful not only for extracting subtle or hidden changes but also for preprocessing transformation before clustering and segmenting the structure of the human brain.

Adolescent↗

PubMed2004

Implicit and explicit processing of kanji and kana words and non-words studied with fMRI.

Using functional magnetic resonance imaging (fMRI), we investigated the implicit language processing of kanji and kana words (i.e., hiragana transcriptions of normally written kanji words) and non-words. Twelve right-handed native Japanese speakers performed size judgments for character stimuli (implicit language task for linguistic stimuli), size judgments for scrambled-character stimuli (implicit language task for non-linguistic stimuli), and lexical decisions (explicit language task). The size judgments for scrambled-kanji stimuli and scrambled-kana stimuli produced activations on the bilateral lingual gyri (BA 18), the bilateral occipitotemporal regions (BA 19/37), and the bilateral superior and inferior parietal cortices (BA 7/40). Interestingly, besides these areas, activations of the left inferior frontal region (Broca's area, BA 44/45) and the left posterior inferior temporal cortex (PITC, BA 37), which have been considered as language areas, were additionally activated during size judgment for kanji character stimuli. Size judgment for kana character stimuli also activated Broca's area, the left PITC, and the left supramarginal gyrus (SMG, BA 40). The activations of these language areas were replicated in the lexical decisions for both kanji and kana. These findings suggest that language processing of both kanji and kana scripts is obligatory to literate Japanese subjects. Moreover, comparison between the scrambled kanji and the scrambled kana showed no activation in the language areas, while greater activation in the bilateral fusiform gyri (left-side predominant) was found in kanji vs. kana comparison during the size judgment and the lexical decision. Kana minus kanji activated the left SMG during the size judgment, and Broca's area and the left middle/superior temporal junction during the lexical decision. These results probably reflect that in implicit or explicit reading of kanji words and kana words (i.e., hiragana transcriptions of kanji words), although using largely overlapping cortical regions, there are still some differences. Kanji reading may involve more heavily visual orthographic retrieval and lexical-semantic system through the ventral route, while kana transcriptions of kanji words require phonological recoding to gain semantic access through the dorsal route.

Adult↗

PubMed2003

Cortical motor areas in plantar response: an event-related functional magnetic resonance imaging study in normal subjects.

The role of the cerebral cortices in normal plantar response was investigated with event-related functional magnetic resonance imaging (fMRI) at 3 Tesla in 12 right-handed normal subjects. During fMRI acquisition, the lateral (LS) and medial (MS) side of the left sole was mechanically stimulated every 16 s to evoke the plantar response under monitoring of the surface electromyogram. LS activated the contralateral supplementary motor area (SMA) more intensively than MS. In contrast, no difference was found in the commonly activated areas including the contralateral primary sensorimotor area, bilateral secondary sensory areas and the thalamus. The results support the hypothesis that the normal plantar response is influenced by the cerebral cortices, and that the SMA likely participates in the regulation of the plantar reflex arc at the spinal level.

Adult↗

PubMed2003

The role of the human supplementary motor area in reactive motor operation.

The role of the supplementary motor area (SMA) in reactive motor operation was investigated with functional magnetic resonance imaging in 13 normal subjects. A visual cue was presented at a regular (1 Hz) or irregular (mean, 1 Hz) rate, and the subject pressed a button with the right index finger in a predictive or reactive manner. Brain regions associated with reactive movement were detected by comparing reactive with predictive movement tasks, and those with irregular movement by comparing irregular and regular cueing tasks. During regular cueing, the SMA showed greater activation for reactive than predictive movement. However, the SMA was equally activated between regular and irregular cueing once the subject reacted to the cue. The SMA is likely involved in reactive adjustment of movement to the external cue.

Adult↗

PubMed2003

A functional magnetic resonance imaging study of internal modulation of an external visual cue for motor execution.

The strategy to perform a task differs according to how a cue is interpreted. In order to investigate the basic mechanisms of temporal regulation in the higher motor areas, the interaction between two different types of internal modulations of an external visual cue was evaluated using functional magnetic resonance imaging (fMRI). An opposing finger movement task guided by dot prompting was employed. In the intermittent tapping experiment, two taps per second and a rest for one second were alternatively repeated in the task blocks. In the constant tapping experiments, the volunteers performed finger movements at 0.5, 1 or 2 Hz. The activation in the primary sensory motor area correlated with the amount of movement. Activities in the supplementary motor area, left dorsal pre-motor area, left superior parietal lobule and right cerebellum depended on the demand for internal modulation. Activation in these areas was maximum for the intermittent task which was a combination of two different internal modulations, and minimum for the 1 Hz movement that did not require internal modulation. It was suggested that these four areas are directly involved in the generation of a complex movement sequence driven by a visual cue, and they are organized for performance. The translation of external pacing and initiation for self-pacing may share the same neuronal basis. Activation in the left supramarginal gyrus, bilateral frontal operticula and basal ganglia did not depend on the combination of the two internal modulations.

Adult↗

PubMed2003

Discrimination of Exner's area and the frontal eye field in humans--functional magnetic resonance imaging during language and saccade tasks.

In the left frontal lobe, Exner's area (EXA), which is responsible for writing and reading, is located close to the frontal eye field (FEF), which is responsible for eye movements. To discriminate EXA from FEF anatomically and functionally, functional magnetic resonance imaging was conducted in 12 healthy volunteers. The saccadic eye movement experiment activated a region defined as the FEF, whereas three language experiments that included translation between grapheme and phoneme activated another region defined as EXA. EXA was found to be located only 1.5 cm apart from the FEF in the Talairach brain template. By conducting the saccade and language experiments in the same individuals, this study was able to successfully separate EXA from FEF.

Adult↗

PubMed2003

Orthography effect on brain activities in 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 1.5 T) 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.

Adult↗

PubMed2003

The effect of task block arrangement on the detectability of activation in fMRI.

The effect of task block arrangements on the detection of brain activation was investigated. Sessions of functional magnetic resonance imaging (fMRI) including the same number of two different task conditions but with different arrangements were compared. The two task conditions were, A) Ellipse-shaped black and white checkerboard flicker stimulation at 4.2 Hz covering the bilateral visual field, and B) the same flicker stimuli covering only the left visual field. In the rest blocks (0), the subjects looked at a fixation point. Four different task block arrangements were compared, 1) A0 (0A0A0A0) and B0 (0B0B0B0), 2) A0B0 (0A0B0A0B0A0B0), 3) AB0 (0AB0AB0AB0) and 4) AB (0ABABAB). Bilateral V1, V2, V3 and the left V5 were activated by condition A, and the right V1 and V2 by B. The activation in the left visual field by A0 was larger than in the other three conditions. In a differential analysis between conditions A and B, activation in the left V3 and V5 was declined by AB0 or AB. When rest blocks were located in the post-stimulus undershoot phase, the % signal change of the BOLD signal was emphasized, which caused augmented significance in the detection of the activity. It was indicated that the outcome of the activation map was influenced by the arrangement of task blocks, even though the same number of task blocks were repeated within the sessions. In fMRI studies, task conditions should be carefully compared within or across sessions considering the characteristics of hemodynamic response functions.

Adult↗

PubMed2003

Finger movements lighten neural loads in the recognition of ideographic characters.

The role of finger writing movements in recognizing Japanese ideographic characters (Kanji) was investigated using functional magnetic resonance imaging at 3 T. A total of 12 healthy native Japanese-speaking volunteers were studied while counting the number of strokes in ideographic characters. In experiment 1, a representation of the pronunciation of an ideographic character was displayed using Japanese syllabic characters. Volunteers were required to count the strokes of the ideographic character corresponding to the displayed phonogram. This procedure included retrieval and generation of ideographic characters. In experiment 2, the ideographic character itself was displayed and the volunteers counted its strokes. This procedure focused on visuospatial imagery processes. Each experiment was conducted under two different motor conditions. One condition allowed the subject to use finger movements to count the strokes, while the other disallowed any finger movements. In both experiments, movement-allowed conditions duly activated the primary motor area. The phonogram-displayed and movement-disallowed condition induced an augmented activation in a part of the left premotor area, which was assumed to be Exner's area. This area might have been activated by a demand for sequential generation of character graphemes that corresponded to the phonogram displayed. The ideographic-character-displayed and movement-disallowed condition activated the dorsal occipitoparietal areas and the primary visual area, which might be involved in the visuospatial mental imagery processes. These results suggest that execution of finger movements during stroke counting of ideographic characters lightens the neural loads for grapheme generation on Exner's area and for the visuospatial imagery processes on the dorsal pathway.

Adult↗

PubMed2002

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 cingulate 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.

Acoustic Stimulation↗