Publications by authors named "Shinichi Urayama"
Article Synopsis
- The study aimed to showcase the effectiveness of small, insertable inductively coupled coils for MR microscopy in a 7T MRI system, focusing on brain specimens from monkeys and mice.
- Two types of coils were constructed (D26 and D64) and tested for their signal-to-noise ratio (SNR) and parallel imaging capabilities compared to a regular knee coil.
- Results showed that the insertable coils significantly improved SNR, provided detailed brain images, and demonstrated ease of use for advanced MR microscopy.
In general, only one diffusion model would be applied to whole field-of-view voxels in the intravoxel incoherent motion-magnetic resonance imaging (IVIM-MRI) study. However, the choice of the applied diffusion model can significantly influence the estimated diffusion parameters. The quality of the diffusion analysis can influence the reliability of the perfusion analysis.
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- Recent observations indicate a timing dissociation between superficial and deep venous systems in relation to brain aging, particularly in normal pressure hydrocephalus, hinting at a shared mechanism linked to ventriculomegaly.
- A comparative study analyzed 225 healthy subjects and 71 traumatic brain injury patients using MRI, revealing distinct patterns in sulcal space and ventricular size that suggest venous drainage plays a role in ventricular enlargement.
- The findings propose that venous insufficiency may contribute to hydrocephalus as a part of normal aging, highlighting the need for non-invasive detection methods and the potential for treatment based on venous function assessment.
Although the relationship between schizophrenia spectrum disorder (SSD) and autism spectrum disorder (ASD) has long been debated, it has not yet been fully elucidated. The authors quantified and visualized the relationship between ASD and SSD using dual classifiers that discriminate patients from healthy controls (HCs) based on resting-state functional connectivity magnetic resonance imaging. To develop a reliable SSD classifier, sophisticated machine-learning algorithms that automatically selected SSD-specific functional connections were applied to Japanese datasets from Kyoto University Hospital (N = 170) including patients with chronic-stage SSD.
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- Recent studies show that blood oxygenation level-dependent (BOLD) signals carry information about brain blood circulation through specific low-frequency oscillations known as systemic low-frequency oscillations (sLFO).
- In a study with 30 volunteers using advanced imaging techniques, researchers found that removing certain components (like neuronal and non-neuronal signals) reduced the reliability of the lag mapping, indicating that the relationship between neural activity and blood flow is complex.
- The lag maps maintained their robustness during various physical tasks, suggesting that they mainly reflect the brain's vascular structure rather than being solely influenced by neuronal activity, which promotes the idea of using BOLD signals for tracking blood flow in the brain.
Article Synopsis
- Studying brain abnormalities in gambling disorder (GD) helps to rule out the influence of neurotoxic substance exposure, enhancing our understanding of addiction overall.
- Previous brain imaging studies on GD have yielded inconsistent results, but the disorder may vary in risk attitudes among individuals.
- Our research examined GD's heterogeneity through a behavioral economics task and MRI scans, revealing specific brain structure changes linked to different levels of loss aversion in GD patients, which could inform more effective treatment strategies.
Lateralization of intrinsic frontoparietal network connectivity and symptoms in schizophrenia.
Psychiatry Res Neuroimaging
February 2017
It has been frequently reported that schizophrenia patients have reduced functional lateralization in the areas related to language processing. Furthermore, there is evidence supporting that schizophrenia patients have disrupted functional connectivity in the bilateral frontoparietal networks (FPNs), of which the left is strongly associated with a cognition-language paradigm, using resting-state functional magnetic resonance imaging (rsfMRI). To examine the laterality of resting-state functional connectivity in schizophrenia, we investigated the bilateral FPNs.
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- The study explores the link between brain structure abnormalities and quality of life in schizophrenia patients, focusing on how these factors interact.
- Researchers compared 33 schizophrenia patients with 42 healthy individuals using MRI scans and the Quality of Life Scale to measure outcomes.
- Findings revealed gray matter reductions in key brain areas for schizophrenia patients, with a specific correlation between the Instrumental Role category of quality of life and gray matter volume in the right anterior insula, influenced by negative symptoms.
Article Synopsis
- Both creativity and schizotypy may arise from an overactive processing of unusual concepts, but results on creativity in schizophrenia vary due to its complex nature.
- A study with 43 schizophrenia patients and 36 healthy participants used brain imaging and fluency tests to assess creativity and delusions, revealing lower creativity and higher delusions in schizophrenia compared to the control group.
- The study found a negative correlation between phonological fluency and delusion severity, with abnormalities in the anterior corpus callosum suggesting that connectivity issues in the brain may differentiate pathological symptoms from adaptive creativity.
Objective: The pathophysiological mechanisms of partial reading epilepsy are still unclear. We delineated the spatial-temporal characteristics of reading-induced epileptic spikes and hemodynamic activation in a patient with partial reading epilepsy.
Methods: Magnetoencephalography (MEG) was recorded during silent letter-by-letter reading, and the source of reading-induced spikes was estimated using equivalent current dipole (ECD) analysis.
To evaluate changes in the visual processing of patients with progressive retinitis pigmentosa (RP) who acquired improved reading capability by eye-movement training (EMT), we performed functional magnetic resonance imaging (fMRI) before and after EMT. Six patients with bilateral concentric contraction caused by pigmentary degeneration of the retina and 6 normal volunteers were recruited. Patients were given EMT for 5 min every day for 8-10 months.
View Article and Find Full Text PDFOcclusion is a primary challenge facing the visual system in perceiving object shapes in intricate natural scenes. Although behavior, neurophysiological, and modeling studies have shown that occluded portions of objects may be completed at the early stage of visual processing, we have little knowledge on how and where in the human brain the completion is realized. Here, we provide functional magnetic resonance imaging (fMRI) evidence that the occluded portion of an object is indeed represented topographically in human V1 and V2.
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- The study investigates how subcortical nuclei contribute to coordinating human behavior, focusing on whether the connectivity of cortico-subcortical circuits is organized in a 'funneling' manner or through 'parallel processing'.
- Using fMRI, researchers analyzed brain activity in 25 healthy volunteers while they performed finger movements, identifying key areas activated during the task.
- The results indicated that there is both overlap and distinct connections between motor cortices and subcortical areas (like the striatum and thalamus), providing evidence for the 'information funneling' hypothesis and suggesting that parallel processing also exists but is not the sole principle in the basal ganglia.
Article Synopsis
- Neurodegenerative diseases like Parkinson's and Alzheimer's progress slowly and vary significantly among individuals, complicating predictions about their long-term progression; recent advancements in biomarker technology have enabled earlier diagnoses but lack a quantitative prediction model.
- Researchers tested a variable-risk model for neurodegeneration kinetics using glaucomatous animals, measuring intraocular pressure (IOP) and white matter integrity to see how well these metrics could predict optic nerve integrity.
- Findings indicate that the variable-risk model, which uses an exponential function based on cumulative risk from IOP measurements, best explains the changes in optic nerve integrity, outperforming other models in predictive accuracy, and also correlates with the number of viable axons.
Article Synopsis
- Diffusion-weighted functional MRI (DfMRI) reacts differently than BOLD-fMRI in the visual cortex, showing faster responses at the start and end of stimuli, suggesting a closer link to neuronal activity.
- Despite also being influenced by BOLD signals, DfMRI shows consistent time-course features outside the visual areas and has less variability between individuals and regions compared to BOLD.
- These findings support DfMRI as a viable method for functional brain imaging and highlight the distinct source of the DfMRI signal.
Article Synopsis
- Researchers studied the diffusion and BOLD components in diffusion-weighted functional MRI (DfMRI) while subjects viewed visual stimuli, focusing on the visual cortex of 16 participants.
- They defined an intrinsic diffusion response function (DRF) that mirrors the hemodynamic response function (HRF) used in BOLD-fMRI, noting that the DRF closely resembles signals from optical imaging related to microscopic brain tissue changes.
- The study found that the HRF contributed 26% to the DfMRI response, primarily affecting the peak amplitude, while the DRF played a crucial role at the onset of the response, and the model was validated with data from 5 additional subjects, revealing some non-linear responses post-stimulation.
Article Synopsis
- Researchers used MRI and near infrared spectroscopy to study how water diffusion and blood oxygen levels change in the brain during visual tasks.
- They found that the water diffusion signal rises and falls faster than the BOLD signal and total hemoglobin levels, indicating it's a quicker response.
- The study suggests that changes in water diffusion might occur before vascular responses, potentially linked to changes in the surrounding brain tissue.
Article Synopsis
- The study explores the use of spin-echo (SE) sequences for T1-weighted brain imaging at 3 Tesla (T), highlighting potential advantages over traditional gradient-echo techniques.
- 18 healthy volunteers were imaged using two sets of T1-weighted sequences: one without a presaturation pulse (PP) and one with PP, including different interleaving methods.
- Results show that interleaved images greatly enhanced the contrast between gray and white matter and that the PP effectively suppressed unwanted signals, indicating that this imaging technique is clinically viable at 3 T.
Article Synopsis
- The study investigated how single-pulse transcranial magnetic stimulation (TMS) affects motor-evoked potentials (MEPs) and brain activity using electromyography and functional MRI in 16 healthy participants.
- Results showed a strong link between the intensity of TMS and MEP amplitude, with increased blood flow in both motor/sensory networks and cognitive areas, indicating both immediate and distant effects of TMS.
- The analysis revealed linear and nonlinear responses in brain activity, suggesting complex interactions in neuron activation beyond just physical movement stimulation, enhancing understanding of how TMS affects brain function.
Article Synopsis
- The study investigates how susceptibility-weighted imaging (SWI) functions under low cerebral blood flow (CBF) conditions caused by hyperventilation (HV).
- Six healthy volunteers were tested with SWI and arterial spin labeling to compare imaging results during normal ventilation and HV.
- Results showed that CBF significantly decreased during HV and that SWI detected noticeable signal changes, indicating its potential usefulness in clinical evaluations of brain blood flow.
Objectives: Some white matter tracts, including the optic radiation (OR), have recently been reported to be delineated as low signal intensity bands (LSBs) on T2*-weighted images at 7 T, presumably because of susceptibility effects caused by myelin.Susceptibility-weighted imaging (SWI) is more sensitive to magnetic susceptibility than T2*-weighted imaging. This study examined whether the LSBs, lateral to the lateral ventricles (LVs) on 3-T SWI, represent the OR.
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- The stereokinetic effect (SKE) is a visual phenomenon where a 2D figure appears to be 3D when it rotates around a person's line of sight.
- Research using functional magnetic resonance imaging (fMRI) identified several brain areas activated by SKE, including the middle temporal complex (hMT+), lateral occipital area (LO), and inferior temporal gyrus (ITG).
- The findings indicate that while there is some overlap in brain activation between SKE and the kinetic depth effect (KDE), specific mechanisms and processing of 3-D objects may vary between these two phenomena.
TAK-599 (known as ceftaroline fosamil) is a novel N-phosphono type prodrug of a cephalosporin compound, T-91825, that exhibits strong activity against methicillin resistant Staphylococcus aureus (MRSA). The stability and stabilization of TAK-599 were investigated by kinetic analysis focused on crystallinity and moisture content. Initially it was planned to develop TAK-599 as an injectable formulation using the amorphous solid powder prepared by lyophilization.
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- This study aimed to compare how well two imaging techniques, susceptibility-weighted imaging (SWI) and T2*-weighted imaging (T2*WI), can detect cerebral microbleeds (MBs) in patients with Moyamoya disease (MMD).
- It included 50 MMD patients and compared the number of detected MBs between the two techniques, assigning a grading score for visualization quality.
- Results showed that SWI identified significantly more MBs (37 in 21 patients) than T2*WI (27 in 16 patients), indicating that SWI is more effective for detecting MBs in this condition.