Hiromasa Takemura, Ph.D
December 8(Fri) - December 8(Fri), 2023
11am
86314 & ZOOM
CNIR seminar
Date: 11 a.m., Fri, Dec 8th
Speaker: Hiromasa Takemura, Ph.D. (National Institute for Physiological Sciences)
Title: Neuroimaging study for structural and functional organization of the human and non-human primate visual system
Abstract: Over the past few decades, significant progress has been made in system neuroscience, advancing our understanding of brain functions by examining the response characteristics of individual brain regions and their relations to behavior. However, there remains a gap in our comprehension of how these brain functions relate to the structural aspects of the nervous system. To address this unresolved question, it is crucial to explore the relationship between the functional organization of the brain and its neuroanatomy. The visual system offers an ideal opportunity to investigate this relationship due to its relatively well-documented functional organization, such as visual field maps, and anatomical connections between regions. In this presentation, I will outline recent studies that delve into the interplay between the functional organization of visual areas and the neuroanatomy of the visual system. First, I will discuss a recent neuroimaging study (Miyata et al., 2022) that evaluates the correlation between the size of the human primary visual cortex (V1) and the optic tract, based on the hypothesis derived from a previous post-mortem work (Andrews et al., 1997). This investigation involves the analysis of data from the Human Connectome Project 7T Retinotopy dataset (Benson et al., 2018) using both fMRI and diffusion-weighted MRI (dMRI). We found a small but robust correlation between V1 size and optic tract tissue properties, suggesting that individual differences in V1 size is correlated with characteristics of retinal ganglion cells, which are reflected in the optic tract measurements. Next, I will delve into a series of studies investigating the relationship between human extrastriate visual field maps (V3A/B and hV4) and the Vertical Occipital Fasciculus (VOF), a white matter tract that connects the dorsal and ventral visual streams (Takemura et al., 2016). Combining data from fMRI and dMRI, these studies suggest that the VOF plays a crucial role in integrating information from the upper and lower visual fields in the human visual system. Furthermore, I will explore the extension of these findings to the non-human primate visual system (Takemura et al., 2017; 2020). Lastly, I will provide a brief overview of other ongoing projects in our lab, including the parcellation of the visual thalamus using quantitative MRI (Oishi et al., 2023) and comparative diffusion MRI studies on visual white matter pathways.