The two-photon compound fiberscope: a universal platform to study the brain at all spatial and temporal scales. – 2P-COMFIB

Understanding how neuronal circuits process information is a major challenge in neuroscience, which demands new tools to address the complexity of the brain during natural functioning. Ideally, we need to be able to record and manipulate at will the activity of every neuron in a circuit in freely behaving animals, with single cell spatial resolution (~ 10 µm), temporal resolutions compatible with the propagation of neuronal activity (~ 1 ms), and at all the spatial scales, from local to long-range circuits involving thousands of neurons across distant (> 5 mm) brain areas. Two-photon (2P) microscopy, combined with holographic light shaping and optogenetic photostimulation, enables to image and manipulate neuronal activity in vivo in mice, but is subject to major limitations. Simultaneous 2P imaging and photostimulation are today only possible in superficial brain regions of head-restrained animals, which limits the validity of the approach for behavioural studies, and can only access limited fields of view (< 1 mm) with low acquisition speeds (< 50 Hz), which is incompatible with the study of signal propagation across distant areas.
In this project I will overcome all limitations and develop 2P-COMFIB, a radically new optical platform, based on bundles of optical fibers, which will completely change the way we study neuronal circuits thanks to two main technologies. 1) A flexible 2P holographic micro-endoscope designed to decipher the links between neuronal circuits and behaviour, which will be capable of kilohertz 2P imaging and precise photostimulation of tens of neurons in deep brain regions of freely moving animals. 2) A 2P kilohertz holographic mesoscope, which will massively scale up the field of view accessible to holographic light shaping and to kilohertz 2P imaging, specifically conceived to image and manipulate neuronal activity with single cell resolution, across different brain areas on temporal scales compatible with the propagation of neuronal signals