title: Holographic photolysis for multiple cell stimulation in mouse hippocampal slices.
abstract: BACKGROUND
  Advanced light microscopy offers sensitive and non-invasive means to image neural activity and to control signaling with photolysable molecules and, recently, light-gated channels. These approaches require precise and yet flexible light excitation patterns. For synchronous stimulation of subsets of cells, they also require large excitation areas with millisecond and micrometric resolution. We have recently developed a new method for such optical control using a phase holographic modulation of optical wave-fronts, which minimizes power loss, enables rapid switching between excitation patterns, and allows a true 3D sculpting of the excitation volumes. In previous studies we have used holographic photololysis to control glutamate uncaging on single neuronal cells. Here, we extend the use of holographic photolysis for the excitation of multiple neurons and of glial cells.
  
  
  RESULTS
  The system combines a liquid crystal device for holographic patterned photostimulation, high-resolution optical imaging, the HiLo microscopy, to define the stimulated regions and a conventional Ca(2+) imaging system to detect neural activity. By means of electrophysiological recordings and calcium imaging in acute hippocampal slices, we show that the use of excitation patterns precisely tailored to the shape of multiple neuronal somata represents a very efficient way for the simultaneous excitation of a group of neurons. In addition, we demonstrate that fast shaped illumination patterns also induce reliable responses in single glial cells.
  
  
  CONCLUSIONS
  We show that the main advantage of holographic illumination is that it allows for an efficient excitation of multiple cells with a spatiotemporal resolution unachievable with other existing approaches. Although this paper focuses on the photoactivation of caged molecules, our approach will surely prove very efficient for other probes, such as light-gated channels, genetically encoded photoactivatable proteins, photoactivatable fluorescent proteins, and voltage-sensitive dyes.
authors.affiliation: Wavefront-Engineering Microscopy Group, Neurophysiology and New Microscopies Laboratory, CNRS UMR 8154, INSERM U603, University Paris Descartes, Paris, France.
authors.forename: Morad
authors.initials: M
authors.lastname: Zahid
authors.forename: Mateo
authors.initials: M
authors.lastname: Vélez-Fort
authors.forename: Eirini
authors.initials: E
authors.lastname: Papagiakoumou
authors.forename: Cathie
authors.initials: C
authors.lastname: Ventalon
authors.forename: María Cecilia
authors.initials: MC
authors.lastname: Angulo
authors.forename: Valentina
authors.initials: V
authors.lastname: Emiliani
mesh_terms: D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology; D006696:Holography / Q000295:instrumentation / Q000379:methods*; D051379:Mice; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D009836:Oligodendroglia / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation; D010782:Photolysis
chemical_list: D002118:Calcium