Simultaneous mesoscopic Ca2+ imaging and fMRI: Neuroimaging spanning spatiotemporal scales

To achieve a more comprehensive understanding of brain function requires simultaneous measurement of activity across a range of spatiotemporal scales. However, the appropriate tools to perform such studies are largely unavailable. Here, we present a novel approach for concurrent wide-field optical and functional magnetic resonance imaging (fMRI). By merging these two modalities, we are for the first time able to simultaneously acquire whole-brain blood-oxygen-level-dependent and whole-cortex calcium-sensitive fluorescent measures of brain activity. We describe the developments that allow us to combine these modalities without compromising the fidelity of either technique. In a transgenic murine model, we examine correspondences between activity measured using these modalities and identify unique and complementary features of each. Our approach links cell-type specific optical measurements of neural activity to the most widely used method for assessing human brain function. These data and approach directly establish the neural basis for the macroscopic connectivity patterns observed with fMRI.