Intravital Microscope with Holographic Photostimulator

• Subject Area: Neurosciences
• Term: Funded in 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 525322704

Our understanding of brain function hinges on the gain of knowledge at different methodological levels. Recording of neuronal activity can inform about the brain functions a neuron is likely involved with. However, to mechanistically describe brain function, neuronal activity needs to be linked to brain function and behavior in a causal manner. Manipulation of neuronal activity at single cell or network level constitutes an important methodological approach for this goal and can be realized via optogenetics. To optogenetically activate neurons with high spatial and temporal precision, the stimulation light needs to be sculpted with dedicated optical stimulators. Here, we request funds for a microscope setup that enables such experiments and consists of a two-photon microscope and a holographic photostimulator. In this system, a spatial light modulator (SLM) is used to generate three-dimensional photo-masks (aka holograms) within the nervous tissue. These holograms are evoked via pre-defined interference patterns of the SLM stimulation light and enable precise spatial control, also along the optical axis. In combination with the imaging arm of the setup, neuronal activity can be measured (calcium imaging) and manipulated (optogenetic holography) at the same time. Further hardware and software additions to the setup allow for simultaneous visual stimulus presentation and recording of additional experimental parameters (e.g. eye positions in vivo). To establish this technology at the University of Tübingen, we need funds for an integrated holographic microscopy setup (without laser). We plan to use this setup in several projects on the visuomotor system in zebrafish (in vivo), visual function in the mouse retina (ex vivo), as well as memory consolidation in sleeping mice (in vivo). One example project will investigate information storage mechanisms in persistently active, recurrent networks, making use of the zebrafish oculomotor hindbrain. The vertebrate hindbrain contains the velocity-to-position neural integrator, which stores information about the current eye position via its persistent activity. Using holographic photostimulation, we will manipulate the activity of functionally identified integrator neurons and observe and interpret the resulting changes in eye position and network activity. These experiments will demonstrate the functional structure of the integrator and reveal the mechanisms of information storage of this persistently active network.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Intravitalmikroskop mit Holographischem Photostimulator
• Instrumentation Group: 5090 Spezialmikroskope
• Applicant Institution: Eberhard Karls Universität Tübingen
• Leader: Professor Aristides Arrenberg, Ph.D.