Effects of Body Temperature Changes on The Cerebral Metabolites and Functional Connectivity in Mice Under...

The temperature of human brain is normally maintained within the physiological range (34°C-39°C) and varies due to warming or cold environments, medical issues, or exercises with the body. As the brain is highly metabolically demanding, how the healthy brain is affected metabolically and functionally by such mild alteration of body temperature remains understudied. In the present study, the effects of the body temperature on the mousebrains were examined with ultrahigh field MRI and MRS. In vivo MR spectroscopy was applied to explore the changes in brain temperature and cerebral metabolites when the rectal temperature of the mice changed from 35 to 37, and 39 degrees Celsius. Meanwhile, diffusion weighted images were collected to assess the cerebrospinal fluid (CSF) diffusivity. Resting-state functional MRI (rsfMRI) was conducted to investigate the functional connectivity (FC) changes of the brain at each body temperature. The evident effects on the brain temperature and metabolites in hippocampus, and diffusivity in CSF were revealed. In particular, the circuit of the ventral hippocampus (vHPC) - anterior hypothalamic nucleus (AHN) is closely associated with stress responses. The effect of body temperature changes on the circuit was examined with rsfMRI, and the associated FC changes may suggest the effect of the mild body temperature increase on stress. In conclusion, the preliminary findings may suggest the brain's sensitivity to the mild body temperature changes and the implication on neuroimaging studies with humans and animals.Clinical Relevance- Body temperature is one of the essential physiological parameters for humans and animals. Our MRI findings suggest that the brain metabolites, diffusivity, and functional connectivity could be affected significantly by mild body temperature changes around the physiological range. Also, the present work highlights the advantage of contemporary ultrahigh field MRI techniques to examine the comprehensive effects of mild temperature changes which are highly relevant to neuroscience studies with humans and animals.