A two-photon compound fiberscope to study the brain at all spatial and temporal scales.

Introduction

Understanding how neuronal circuits process information is a major scientific challenge, which demands new tools to address the complexity of the brain in animals during natural functioning. Two-photon (2P) microscopy, combined with optogenetics, has revolutionized neuroscience thanks to the possibility to image and photostimulate neuronal activity with light, but suffers from important limitations.

Limitations of Current Techniques

To determine how perception and behaviour arise, we need to record and manipulate at will the activity of every neuron in a circuit in freely behaving animals. 2P microscopy is, on the contrary, mainly performed in head-fixed animals, which poses a clear limitation to the study of natural behaviour.

At the same time, understanding how different brain areas exchange information requires:

1. Maintaining single cell spatial resolution (~ 15 μm)
2. Achieving temporal resolutions compatible with the propagation of neuronal signals (~ 1 ms)
3. Covering ultra large spatial scales (5 mm)

These requirements are today completely out of reach for 2P microscopy.

Project Goals

In this project, I will overcome these limitations and develop the 2P compound fiberscope, a new optical technique based on the unique combination of multiple optical fibers and optimal spatial and temporal beam shaping approaches. This will completely change the way we study neuronal circuits thanks to two main technologies:

1. A flexible 2P micro-endoscope to image and photostimulate neurons in freely moving animals, which will give access to entire brain regions with the highest imaging and manipulation efficiency and the fastest acquisition speed.
2. The first 2P mesoscope specifically conceived to image and manipulate neuronal activity with single cell resolution across the majority of the mouse cortex on temporal scales compatible with the propagation of neuronal signals.

Conclusion

These technologies will pave the way for a real understanding of how neuronal circuits drive behaviour and how different brain regions communicate to process neuronal information.