Construction of the common cortical space by spontaneous activity and its application in the mouse cortex

Wide-field optical imaging of the animal brain is a useful technique for measuring brain dynamics, including spatial structure. However, quantitative inter-animal comparison is difficult due to lack of the common cortical space that can normalize individually imaged brains as done in human functional MRI studies. Here, by using wide-field functional Ca²⁺ imaging on anesthetized transgenic mice expressing G-CaMP7 in astrocytes and excitatory neutrons, we attempted to establish the common cortical space in mice, which can be useful as a standard of functional brain map. We initially reconstructed cortical areas embedded within spontaneous activity as the functional connectivity maps for the individual mice, then matched them in size, shape, and location across mice by geometric transformation. Finally, we assigned all the recorded signals into the transformed space, to make spatially normalized signals in the common cortical space. Using this method, we managed to extract activity patterns commonly observed across mice. These results suggest that the presented method is available to facilitate inter-animal comparison of brain dynamics, and has the potential to identify common brain activity across animals.