The combination of light microscopy and optogenetics offers the possibility to control activation and inhibition of neuronal activity enabling the analysis of well-defined neuronal population within intact neuronal circuits and systems. Interestingly, optogenetics has already permitted to address key biological questions with relatively simple illumination methods using widefield visible light illumination. However, some limitations in the specificity of genetic targeting and the intricate morphology of the brain make it challenging to, for example, individuate subsets of genetically identical interconnected cells, or to establish the role of specific spatiotemporal excitatory patterns in guiding animal behavior. To reach such degree of specificity, more sophisticated illumination methods are required. Here I will present a series of new methods recently developed in my laboratory for precise activation of optogenetics channels, based on the temporal control of ultrafast pulses for axial localization of the illumination volume and on either digital holography or the generalized phase contrast method for lateral light patterning. Exemplary experiments showing two-photon activation of ChR2, one of the most used optogenetic channels, in brain slices will be showed. I will also present some recent results showing that both axial resolution and lateral light shape of temporally focused beams are impressively robust to scattering permitting photoactivation of ChR2 at depth greater than 200um.


Monday, September 23, 2013, 12:00. Seminar Room

Hosted by Romain Quidant / Lluís Torner