1 PhD position at Wavefront engineering microscopy group. Photonics Departement of the Institut de la Vision, Paris

"Development of an optimal two-photon holographic micro-endoscope for the optogenetic imaging and control of neuronal activity in deep brain structures"

Valentina Emiliani
Nicolò Accanto

Project. The recent availability of optogenetic sensors and actuators, capable of reading and manipulating neuronal activity with light, as well as the parallel development of advanced optical techniques to precisely control the propagation of laser beams, have recently enabled experiments in which selected subgroups of neurons in a considerable volume could be precisely interrogated1. Today, optogenetics and neurophotonics are thriving research fields with new technical developments and discoveries happening on a daily basis. Our group has been one of the main actors in developing advanced optical techniques for the study of neurons and neuronal circuits, mainly based on the wavefront shaping of ultrafast laser pulses and two-photon (2P) effects 2,3.

In order to mimic naturally occurring neuronal circuits, it is necessary to manipulate (or photo-stimulate) individual neurons, arbitrarily arranged in the three dimensions at specific deep locations in the brain. As a solution to the former problem, we developed multiplexed temporally focused light shaping (MTF-LS) 3, a technique capable of precisely address in the 2P regime many different targets in a large volume. Scattering from biological tissues is however still a major obstacle to the use of light in neuroscience. MTF-LS, as any optical technique, is limited by scattering to the investigation of superficial brain regions (few hundred μm below the surface) whereas many important brain structures are located at much larger depths. We recently made the first step towards the study of deeper regions by developing a basic micro-endoscope (ME) through which MTF-LS could be performed 4. However, such first implementation still suffers from important limitations that need to be overcome. In this project, starting from the design of Ref. 4, the candidate will overcome current limitations and develop a new class of optimal two-photon micro-endoscopes for the simultaneous 2P imaging and precise 2P optogenetic photo-stimulation of many neurons in large volumes. The candidate will follow every stage of the project, including: (i) the development of dedicated wavefront shaping solutions (e.g. computer generated holography, adaptive optics, pulse shaping) to control the propagation of ultrafast laser pulses through the ME; (ii) the design and test (both experimentally and through simulations) of optimized optical probes to outperform currently available ones; (iii) the construction of the optical setup comprising two different ultrafast laser sources and the ME; (iv) proof of principle in vitro and in vivo experiments in collaboration with biologists in the group.

PhD profile. We seek for a highly motivated and creative student, with a strong interest in mastering both the theory and experimental implementation of advanced nonlinear optical techniques (Fourier optics, computer generated holography 5, temporal focusing 6, two-photon microscopy) as well as in applying them to neurobiology. The candidate will work in a highly interdisciplinary and international environment, involving physicists, engineers and biologists. Team working capability and flexibility are therefore necessary. Personal initiative during the whole project will be highly encouraged. The PhD candidate must hold a master’s degree in physics or engineering. Previous training in optics and/or expertise in programming (MATLAB, Python, LabView) will be positively evaluated.

Funding for three years is already secured.

Host lab
The project will be carried out at  the Vision Institute.
The Vision Institute / 15-20 National Ophthalmology Hospital also gathers many scientists, mostly biologists or clinicians, around the function and diseases of the vision and eye.

1. Emiliani et al. (2015), J. Neurosci., 35, 13917, DOI: 10.1523/JNEUROSCI.2916-15.2015
2. Papagiakoumou et al. (2010), Nat. Methods, 7, 848, DOI: 10.1038/nmeth.1505
3. Accanto et al. (2018), Optica, 5, 1478, DOI: 10.1364/OPTICA.5.001478
4. Accanto et al. (2019), Sci. Rep., 9, 7603, DOI: 10.1038/s41598-019-43933-w
5. Lutz et al. (2008), Nat. Methods, 5, 821, DOI: 10.1038/nmeth.1241
6. Oron et al. (2005), Opt. Express, 13, 1468, DOI: 10.1364/OPEX.13.001468