IN SITU IMAGING OF RETINAL CALCIUM DYNAMICS IN AWAKE ANIMALS

Mammalian vision starts in the retina. The study of retinal circuits in vivo is essential for comprehending retinal neural dynamics under physiological conditions. While several transpupillary retina imaging techniques have been utilized in anesthetized animals, the in situ imaging of retinal activity in awake animals has been more difficult to accomplish. These limits have frustrated crucial scientific inquiries, such as how visual processing in the retina is modulated by behavior. In this study, we present novel experimental approaches that stabilize the eye to access in situ retinal dynamics with optical techniques in awake mice. Our findings demonstrate that this method can be utilized to: 1) image neural activity in distinct cell types across multiple ages, 2) record meso-scale (e.g. spontaneous retinal waves) or cellular retinal dynamics, 3) study retina functional connectivity in vivo, and 4) pharmacologically manipulate retinal activity. We applied these novel approaches to demonstrate that retinal activity is strongly modulated by movement through H1R-dependent histaminergic transmission in vivo, even at the amacrine cell level. These methods are suitable to simultaneously record retinal and brain activity dynamics or to investigate retinal responses to patterned visual stimuli, making accessible fundamental questions about visual processing that have previously been very challenging to achieve.