Email:  olivier.dupont-therrien.1@ulaval.ca
Position: PhD Student – Biophotonics, Université Laval
Academia: MSc, BSc – Physics, Université Laval
Advisors: Prof. Daniel Côté, Prof. Paul De Koninck

RESEARCH INTERESTS: Functional imaging, Temporal Focusing, Patterned illumination

WIDE-FIELD MULTIPHOTON IMAGING OF CELLULAR DYNAMICS IN THICK TISSUE

To understand circuit function, strategies to monitor the activity of a large number of neurons at high speed in vivo are necessary. Optical methods based on beam scanning, such as two-photon microscopy, have the capacity to access neurons within surface layers of the brain, but are less suitable for high speed network imaging. Wide-field temporal focusing is a technique that provides optical sectioning for imaging without the need for beam scanning. However, illuminating over large areas greatly reduces the photon density which limits the technique applicability to small regions, precluding functional imaging of cellular networks. Here, we report the first use of temporal focusing combined with spatial light modulation to create a fast imaging modality for functional neuronal activity measurements.

Our strategy combines beam shaping and temporal focusing of amplified pulses for fast imaging of cells from the central nervous system in acute slices. We show multiphoton video-rate imaging with an optical sectioning under 10 μm at 800 nm, leading to imaging of calcium dynamics of multiple cells simultaneously in brain slices. It is also shown that out-of-focus fluorescence background rejection by temporal focusing of amplified pulses leads to an improved signal-to-background ratio when monitoring the spontaneous variations in free calcium ion concentration in cells from neuronal acute slices. With beam shaping, addressing of individual neurons is achievable and makes it possible to combine the sensing of activity with optical stimulation for analysis of network communication. The combined fast imaging and optical sectioning capabilities of this approach open the way to also probe voltage fluctuations within neural networks in brain slices or in vivo over large regions simultaneously.