Technologies for real-time molecular and cellular imaging in live animals

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The goal of neuroscience is to understand how the nervous system organizes itself at molecular, cellular and network levels to process signals into information. Experimental paradigms with live animals and their intact nervous system are therefore absolutely necessary. However, this research effort is greatly impeded by our limited ability to observe the intact nervous system in a live animal at the appropriate level, be it molecular, cellular or systemic. My group works in close collaboration with a team of neurobiologists to address this lack of appropriate tools with photonics-based technology. This is a lengthy process that has its origin in demonstrating how judiciously chosen physical phenomena can be used to extract previously unobtainable information, or how the integration of several notions from beam shaping and optical design can lead to novel devices with highly desirable properties to study the live nervous system. The purpose of this NSERC Discovery grant is to feed the proof-of-concept program that makes possible the development of such tools with students from physical sciences and engineering. The overall vision of this research program is to develop novel label-free imaging methods to assess the structure and function of the nervous system at molecular, cellular and systemic levels, and develop the necessary technologies to overcome the many challenges associated with their use for live animal imaging. To do so, we tackle two specific problems (animal movement and lipid membrane order) and address them with projects that require an intimate knowledge of light-matter interactions and optical design. First, we will develop a system for real-time measurement of animal position that is adaptable to all confocal and multiphoton imaging systems. The use of a special lens in a secondary illumination path will allow the detection of the surface of the tissue, which will then be used either to adjust the position of the objective for closed-loop stabilization, or to measure and label the position of the frames and reconstruct a 3D image despite animal movement. Second, we propose to use polarization-sensitive coherent Raman imaging to image the molecular order of lipid membranes such as myelin.  The coherent Raman process has been used for years to image the lipids of myelin (white matter), and can yield endogenous images of the white matter in the nervous system.  Here we will turn to our advantage the polarization-sensitivity of the coherent Raman process to extract the molecular order of lipids within myelin with a set of images at different polarizations.  This will be made possible thanks to a novel strategy to compensate polarization distortion introduced by the optical components of the microscope. With this innovative system, we will be able to perform these molecular order measurements rapidly and robustly to extract previously unobtainable information.