ABSTRACT
Perception and cognition arise from the coordinated activity of large networks of neurons spanning diverse brain
areas. Understanding their emergent behavior requires large-scale activity measurements both within and across
regions, ideally at single cell resolution. An integrative understanding of brain dynamics requires cellular-scale
data across sensory, motor, and executive areas spanning more than a centimeter. In addition, functional
interactions between brain areas vary with motivational state and behavioral goals, making data from freely
moving animals particularly critical. Thus, a key goal is the ability to measure activity across the full extent of
cortex at cellular resolution as animals engage in complex, cognitively demanding behaviors. However,
conventional fluorescence microscopy techniques cannot meet the joint requirements of FOV, resolution, and
miniaturization. Here, we propose a Computational Miniature Mesoscope (CM2) that will enable cortex-
wide, cellular resolution Ca2+ imaging in freely behaving mice. The premise is that computational imaging
leverages advanced algorithms to overcome limitations of conventional optics and significantly expand imaging
capabilities. In our proof-of-principle system, we demonstrated single-shot 3D imaging across an 8x7mm2 FOV
and 7µm resolution in scattering phantoms (Sci. Adv. 2020), and achieved single-cell resolution on histological
sections. Our wearable prototype has now demonstrated visualization of sensory-driven neural activity across
the 4x4mm2 main olfactory bulb in both head-fixed and freely moving mice. In this project we will: (Aim 1)
advance CM2 hardware to achieve cortex-wide cellular resolution imaging. We will validate the hardware
improvement on both phantoms and in vivo experiments. (Aim 2) Develop scattering-informed deep learning for
fast and robust recovery of neural signals. We will validate the algorithm on in vivo experiments and benchmark
against tabletop 1P and 2P measurements. (Aim 3) Cortex-wide, cellular-resolution Ca2+ imaging during social
recognition in freely behaving mice. We will use CM2 to investigate the cross-area, network-scale activity
dynamics that guide social interactions between familiar partners - one of the most integrative, multi-sensory,
and cognitively demanding forms of neural processing. IMPACT ON PUBLIC HEALTH: This work will establish
powerful enabling technology that greatly expands the scale of activity measurements possible in behaving
animals, providing access to a wide range of questions about distributed cortical function. As a focused
application, we will test the neural signatures of individual recognition during social behavior. We anticipate that
our approach can be extended to a broader range of biological questions such as navigation, short- and long-
term memory storage, and can potentially lead to new strategies for characterizing the disruptions in neural
function that occur in psychiatric disease and neurodegenerative disorders.