Brain-wide functional mapping by ultrahigh field fMRI in mice

초록

Functional magnetic resonance imaging (fMRI) is an indirect method to produce images of cerebral activity based on the detection of local changes in blood flow and oxygenation induced by neuronal activity. Animal (mouse) fMRI studies, utilizing the same imaging signals as human brain mapping, provide valuable insights into understanding brain functions through minimally invasive neuronal modulation and transgenic models. One of the goals in modern neuroscience is understanding complex circuit-specific and network-level brain processing. Brain regions are interconnected through a combination of feedforward and feedback, or bottom-up and top-down projections, forming intricate networks. To further advance understanding of brain functions, we conducted fMRI-based studies on two main objectives: 1) Determining the direction of information flow within the brain 2) Investigating the contributions of different circuits to functional activities For these works, we utilized fMRI with optogenetic modulations in mice at an ultrahigh field of 15.2 T. We demonstrated that the spatiotemporal dynamics of fMRI signals putatively reflect the flow of neural activation, indicating that ultrahigh-resolution fMRI at ultrahigh fields can be utilized to map information flow across the entire brain. Furthermore, fMRI combined with neuronal modulation successfully determined the relative contribution of each circuit to fMRI responses on whole brain, which could complement conventional microscopic functional circuit studies by elucidating brain-wide, population-based information processing.