Hiromasa Takemura

Hiromasa Takemura
The Graduate University for Advanced Studies | SOKENDAI · National Institute for Physiological Sciences

Ph.D

About

76
Publications
8,462
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
680
Citations
Introduction
Hiromasa Takemura currently works at the National Institute for Physiological Sciences, Japan. Hiromasa's current research interest is to use neuroimaging to clarify relationship between structure and function of human brains.
Additional affiliations
September 2021 - present
National Institute for Physiological Sciences
Position
  • Professor
April 2021 - present
National Institute of Information and Communications Technology
Position
  • Senior Researcher
April 2018 - March 2021
National Institute of Information and Communications Technology
Position
  • Faculty Member
Education
April 2009 - March 2012
April 2007 - March 2009
April 2003 - April 2007

Publications

Publications (76)
Article
Full-text available
The human brain has the capacity to drastically alter its somatotopic representations in response to congenital or acquired limb deficiencies and dysfunctions. The main purpose of the present study was to elucidate such extreme adaptability in the brain of an active top wheelchair racing Paralympian (participant P1) who has congenital paraplegia (d...
Preprint
The human brain has the capacity to drastically alter its somatotopic representations in response to congenital or acquired limb deficiencies and dysfunctions. The main purpose of the present study was to elucidate such extreme adaptability in the brain of an active top wheelchair racing Paralympian (participant P1) who has congenital paraplegia (d...
Article
Full-text available
Purpose: Glaucoma is a disorder that involves visual field loss caused by retinal ganglion cell damage. Previous diffusion magnetic resonance imaging (dMRI) studies have demonstrated that retinal ganglion cell damage affects tissues in the optic tract (OT) and optic radiation (OR). However, because previous studies have used a simple diffusion ten...
Preprint
Full-text available
Individual differences among human brains exist at many scales, spanning gene expression, white matter tissue properties, and the size and shape of cortical areas. One notable example is an approximately 3-fold range in the size of human primary visual cortex (V1), a much larger range than is found in overall brain size. A previous study (Andrews e...
Preprint
Full-text available
Purpose Glaucoma is a disorder that involves visual field loss caused by retinal ganglion cell damage. Previous diffusion magnetic resonance imaging (dMRI) studies have demonstrated that retinal ganglion cell damage affects tissues in the optic tract (OT) and optic radiation (OR). However, because previous studies have used a simple diffusion tenso...
Article
Full-text available
The superior longitudinal fascicle/fasciculus (SLF) is a major white matter tract connecting the frontal and parietal cortices in humans. Although the SLF has often been analyzed as a single entity, several studies have reported that the SLF is segregated into three distinct branches (SLF I, II, and III). They have also reported the right lateraliz...
Preprint
Full-text available
The superior longitudinal fascicle/fasciculus (SLF) is a major white matter tract connecting the frontal and parietal cortices in humans. Although the SLF has often been analyzed as a single entity, several studies have reported that the SLF is segregated into three distinct branches (SLF I, II, and III). They have also reported the right lateraliz...
Preprint
Full-text available
The human lateral geniculate nucleus (LGN) is composed mainly of the magnocellular and parvocellular subdivisions. The non-invasive identification of these subdivisions is, however, difficult due to the small size of the LGN. Here we propose a method to identify these subdivisions by combining two structural MR measures: high-resolution proton-dens...
Article
Identifying the plastic and stable components of the visual cortex after retinal loss is an important topic in visual neuroscience and neuro-ophthalmology. Humans with juvenile macular degeneration (JMD) show significant blood-oxygen-level-dependent (BOLD) responses in the primary visual area (V1) lesion projection zone (LPZ), despite the absence o...
Article
Full-text available
Although the primate visual system has been extensively studied, detailed spatial organization of white matter fiber tracts carrying visual information between areas has not been fully established. This is mainly due to the large gap between tracer studies and diffusion-weighted MRI studies, which focus on specific axonal connections and macroscale...
Article
Full-text available
Although the primate visual system has been extensively studied, detailed spatial organization of white matter fiber tracts carrying visual information between areas has not been fully established. This is mainly due to the large gap between tracer studies and diffusion-weighted MRI studies, which focus on specific axonal connections and macroscale...
Article
Full-text available
Although the primate visual system has been extensively studied, detailed spatial organization of white matter fiber tracts carrying visual information between areas has not been fully established. This is mainly due to the large gap between tracer studies and diffusion-weighted MRI studies, which focus on specific axonal connections and macroscale...
Article
Full-text available
Although the non-invasive measurement of visually evoked responses has been extensively studied, the structural basis of variabilities in latency in healthy humans is not well understood. We investigated how tissue properties of optic radiation could predict inter-individual variability in the latency of the initial visually evoked component (C1),...
Article
Full-text available
The primate brain contains a large number of interconnected visual areas, whose spatial organization and intracortical projections show a high level of conservation across species. One fiber pathway of recent interest is the vertical occipital fasciculus (VOF), which is thought to support communication between dorsal and ventral visual areas in the...
Article
Full-text available
Neural oscillations at ∼10 Hz, called alpha oscillations, are one of the most prominent components of neural oscillations in the human brain. In recent years, characteristics (power/frequency/phase) of occipital alpha oscillations have been correlated with various perceptual phenomena. However, the relationship between inter-individual differences...
Article
Full-text available
Historically, the primary focus of studies of human white matter tracts has been on large tracts that connect anterior-to-posterior cortical regions. These include the superior longitudinal fasciculus (SLF), the inferior longitudinal fasciculus (ILF), and the inferior fronto-occipital fasciculus (IFOF). Recently, more refined and well-understood tr...
Preprint
Historically, the primary focus of studies of human white matter tracts has been on large tracts that connect anterior to posterior cortical regions. These include the superior longitudinal fasciculus (SLF), the inferior longitudinal fasciculus (ILF), and the inferior fronto-occipital fasciculus (IFOF). Recently, more refined and well understood tr...
Article
Full-text available
In patients with retinal ganglion cell diseases, recent diffusion tensor imaging (DTI) studies have revealed structural abnormalities in visual white matter tracts such as the optic tract, and optic radiation. However, the microstructural origin of these diffusivity changes is unknown as DTI metrics involve multiple biological factors and do not co...
Article
Full-text available
Stereopsis is a fundamental visual function that has been studied extensively. However, it is not clear why depth discrimination (stereoacuity) varies more significantly among people than other modalities. Previous studies have reported the involvement of both dorsal and ventral visual areas in stereopsis, implying that not only neural computations...
Article
Full-text available
Comparative neuroanatomy studies improve understanding of brain structure and function and provide insight regarding brain development, evolution, and also what features of the brain are uniquely human. With modern methods such as diffusion MRI (dMRI) and quantitative MRI (qMRI), we are able to measure structural features of the brain with the same...
Preprint
Full-text available
Stereopsis is a fundamental visual function that has been studied extensively. However, it is not clear why depth discrimination (stereoacuity) varies more significantly among people than other modalities. Previous studies reported the involvement of both dorsal and ventral visual areas in stereopsis, implying that not only neural computations in c...
Article
Full-text available
Recent advances in diffusion-weighted MRI (dMRI) and tractography have enabled identification of major long-range white matter tracts in the human brain. Yet, our understanding of shorter tracts, such as those within the parietal lobe, remains limited. Over a century ago, a tract connecting the superior and inferior parts of the parietal cortex was...
Conference Paper
While alpha oscillations modulate various aspects of visual processing, their functional roles in visual perception are unclear. Our previous study (Minami and Amano, VSS2016) showed a tight relationship between alpha oscillations and an illusory jitter, called the motion-induced spatial conflict (MISC; Arnold & Johston, 2005). The MISC is a phenom...
Conference Paper
Full-text available
Two common approaches to tractography seeding are using the whole-brain white matter mask, or the gray and white matter interface. Using a dataset with two acquisitions per subject and a state of the art processing pipeline, we compared the test-retest reproducibility of the shape and tract profiles of major white matter bundles for both seeding st...
Preprint
Recent advances in diffusion-weighted MRI (dMRI) and tractography have enabled identification of several long-range white matter tracts in the human brain. Yet, our understanding of shorter tracts, such as those within the parietal lobe, remains limited. Over a century ago, a tract connecting the superior and inferior parts of the parietal cortex w...
Article
We compare several major white-matter tracts in human and macaque occipital lobe using diffusion magnetic resonance imaging. The comparison suggests similarities but also significant differences in the tracts. There are several apparently homologous tracts in the 2 species, including the vertical occipital fasciculus (VOF), optic radiation, forceps...
Article
Full-text available
Visual neuroscience has traditionally focused much of its attention on understanding the response properties of single neurons or neuronal ensembles. The visual white matter and the long-range neuronal connections it supports are fundamental in establishing such neuronal response properties and visual function. This review article provides an intro...
Preprint
Full-text available
Visual neuroscience has traditionally focused much of its attention on understanding the response properties of neurons along the visual pathways. This review focuses instead on the properties of the white matter connections between these neurons. Specifically, we provide an introduction to methods to study the human visual white matter using diffu...
Preprint
We compare the major white matter tracts in human and macaque occipital lobe using diffusion MRI. The comparison suggests similarities but also significant differences in spatial arrangement and relative sizes of the tracts. There are several apparently homologous tracts in the two species, including the vertical occipital fasciculus (VOF), optic r...
Article
Full-text available
Tractography uses diffusion MRI to estimate the trajectory and cortical projection zones of white matter fascicles in the living human brain. There are many different tractography algorithms and each requires the user to set several parameters, such as curvature threshold. Choosing a single algorithm with specific parameters poses two challenges. F...
Data
Example of crossing fascicle voxel in which ETC shows optimal performance. a. Measured and predicted diffusion signal from one example voxel (from Subject 5, STN96 dataset). Horizontal axis depicts the diffusion gradient directions (arbitrary order) and vertical axis depicts the magnitude of demeaned diffusion signal in each direction. Black lines...
Data
Comparison between ETC and SPC using large candidate connectome size. a. Flow diagram of BigSPC model. We generate the identical number of streamlines to ETC only using single parameter (minimum radius of curvature = 2 mm), and optimized it using LiFE (see S1 Text, Section 2). b. Optimized connectome size. BigSPC supports comparable number of strea...
Data
ETC-preselection model. a. Flow diagram of the ETC-preselection (‘ETCpre’; see S1 Text, Section 5). Using LiFE, we optimize each SPC first, and select streamlines contributing diffusion signal prediction in each SPC. We combine those preselected streamlines to create candidate ETCpre connectome, and optimized it using LiFE again. See S1 Text, Secti...
Data
The relation between curvature and angle threshold in tractography. The plot describes the relationship between the minimum radius of curvature and angle threshold when step size is 0.2 mm, based on the formula in Tournier et al. (2012) [18]. (EPS)
Data
Comparison of connectome models from Human Connectome Project (HCP) data. a. Optimal connectome size in 8 hemispheres from HCP90 dataset (occipital cortex). Error bar depicts ±1 s.e.m. across hemispheres. Conventions are identical to those in Fig 4a and 4b. Distribution of radius of curvature in optimized connectome in six connectome models (SPCs a...
Data
Streamline curvature distribution of whole-brain connectomes generated by PICo. Distribution of the radius of curvature in candidate connectome in four different whole-brain connectome, each of which is generated by using four different angle threshold (5.7, 11,5, 23.1, 47.2 deg) in PICo algorithm [11] on Camino toolbox (see S1 Text, Section 1). We...
Data
Ensemble Tractography using multiple tractography algorithms. a. Flow diagram of Ensemble Tractography across algorithms (see S1 Text, Section 3). Using three different tractography algorithms in MRtrix (DT_STREAM: Tensor deterministic; SD_STREAM: CSD deterministic, and SD_PROB: CSD probabilistic; [18]), we generated three Single Algorithm Connecto...
Data
Ensemble Tractography comparing across stopping criterion. a. Flow diagram of Ensemble Tractography across Fiber Orientation Distribution (FOD) amplitude stopping criterion (see S1 Text, Section 4). Using four different FOD amplitude stopping criterions (0, 0.05, 0.1 and 0.2) in MRtrix, we generated four SPCs containing 160,000 streamlines in occip...
Data
Waypoint ROIs for identifying the U-fiber in occipital white matter. Colored regions depict two white matter regions used for identifying U-fiber. Streamlines having one endpoint for each ROI are identified as U-fiber. a. Subject 1, left hemisphere in STN96 dataset. b. Subject 6, left hemisphere in HCP90 dataset. (EPS)
Data
Occipital white matter regions used for the analysis for STN96 dataset. White matter regions used for the main analysis (Figs 3–5) in left (red) and right (blue) hemisphere from 5 subjects in STN96 dataset. The boundary of the white matter regions in each hemisphere is described in ACPC coordinate. (EPS)
Data
Streamline curvature distribution of candidate connectomes. Distribution of the radius of curvature in candidate connectome in six connectome models. Conventions are identical to Fig 3. (EPS)
Article
Full-text available
Human visual cortex comprises many visual field maps organized into clusters. A standard organization separates visual maps into 2 distinct clusters within ventral and dorsal cortex. We combined fMRI, diffusion MRI, and fiber tractography to identify a major white matter pathway, the vertical occipital fasciculus (VOF), connecting maps within the d...
Article
Full-text available
Purpose: Patients with Leber hereditary optic neuropathy (LHON) and cone-rod dystrophy (CRD) have central vision loss; but CRD damages the retinal photoreceptor layer, and LHON damages the retinal ganglion cell (RGC) layer. Using diffusion MRI, we measured how these two types of retinal damage affect the optic tract (ganglion cell axons) and optic...
Conference Paper
Over the last several decades, visual neuroscientists have learned how to use fMRI to identify multiple visual field maps in the living human brain. Several theories have been proposed to characterize the organization of these visual field maps, and a key theory with substantial support distinguishes dorsal stream involving with spatial processing...
Article
Full-text available
A physically stationary stimulus surrounded by a moving stimulus appears to move in the opposite direction. There are similarities between the characteristics of this phenomenon of induced motion and surround suppression of directionally selective neurons in the brain. Here, functional magnetic resonance imaging was used to investigate the link bet...
Conference Paper
Full-text available
A physically stationary stimulus appears to move in the direction opposite to surrounding motion (induced motion). Although previous studies have argued similarities between induced motion and surround suppression of direction-selective neurons in macaque areas MT and MSTl, the relationship between subjective perception of induced motion and cortic...