Human Brain Mapping of Autonomic Functions

Abstract

The hypothalamus contains several sub-nuclei that regulate autonomic functions such as hunger and thirst. The hypothalamus is a small structure of less than 1 cubic centimeter in each hemisphere of the human brain, and very little is known about precise anatomical organization and functional properties of the hypothalamus in the human brain. In this study, in collaboration with departments of endocrinology and radiology, high-resolution fMRI was conducted, while blood glucose level was monitored (Figure-1). Cubic voxels of 1.25 mm were employed, rather than standard high-resolution fMRI of 2 mm cubic voxels, which allowed us to divide the human hypothalamus into several sub-regions using a boundary mapping method based on the resting-state functional connectivity. The defined sub-regions were used to track fMRI signal time-courses when the blood glucose level was manipulated by OGTT. Our preliminary results showed prominent signal changes after OGTT in specific sub-regions in the hypothalamus, and promise future studies of mapping autonomic functions in the human hypothalamus.