Congratulations to our new FdV doctor Francesca ANSELMI, who graduated with the "very honourable" grade and Congratulations of the jury on november 4th 2011.
Thesis title : Advanced optical methods for brain activity control
Francesca Anselmi (center) with Aurélien Begue (PhD fellow) and Cathie Ventalon (co-supervisor)
Brain stimulation with light has become a fundamental tool in neuroscience, thanks to the
advent of photosensitive molecules, such as caged-neurotransmitters, optogenetic ion channels and
pumps. To fully exploit the potentialities of these novel compounds and achieve complete spatio-
temporal control of neuronal activity, it is necessary to develop new efficient ways to deliver light into
brain preparations. In this work, we presented two novel optical systems for spatial light patterning by
phase modulation and demonstrated their application to photostimulation of neuronal activity.
In the first project, we implemented an optical system for two-photon photoactivation, combining
Generalized Phase Contrast for lateral shaping of the illumination profile, and Temporal Focusing for
axial confinement of excitation patterns. We used this system for two-photon stimulation of cortical
neurons expressing the light-sensitive ion channel Channelrhodopsin-2.
To further extend photostimulation to brain structures organized into complex volumes, we developed
a second technique, allowing three-dimensional photoactivation by digital holography, and
simultaneous imaging with a remote focusing system along arbitrary planes, either axially displaced
or tilted with respect to the principal focal plane. This method was used to perform scanless widefield
calcium imaging of oblique dendrites, after stimulation by glutamate photolysis at multiple positions.
Keywords: phase modulation, two-photon, generalized phase contrast, temporal focusing,
optogenetics, channelrhodopsin, three-dimensional imaging, remote focusing, digital holography,
calcium imaging, photolysis, dendrite.
Members of the jury :
Dr. Valentina EMILIANI (supervisor)
Dr. Cathie VENTALON (co-supervisor)
Dr. Stéphane DIEUDONNE (reporter)
Pr. Michael HAUSSER (reporter)
Pr. Claire LEGAY (president)
Dr. Sylvain GIGAN (examiner)