BRAIN EAGER: Panoramic, dynamic, multi-region two-photon microscopy for systems neuroscience

This award is made by the Instrument Development for Biological Research program (IDBR)in the Division of Biological Infrastructure (DBI; BIO Directorate).

The cerebral cortex, the outer layer of brain, has greatly expanded in surface are during mammalian evolution. This cortical region is parcellized into discrete functional areas including visual cortex, motor cortex, and language areas. These brain areas act in concert to support behavior. Although we have learned much about how to ascribe function to particular brain areas, we know little about the cellular mechanisms by which this concert is conducted. Model systems, including mice have discrete functional areas in their brains. However, the current tools that neuroscientists have for investigating activity in brains are limited to either a sparse sampling of neurons distributed over large areas, or a large density of neurons in a single area just 500-700 microns across. Thus, it is tremendously difficult to make progress in understanding how cortical areas act in concert to support behavior. The proposed research project will develop a new type of microscope which will be able to detect single neuron spiking across a field of view of several millimeters. This area can encompass five or more cortical areas in a mouse. In addition, this microscope will contain high speed spotlights for simultaneously imaging neuronal activity in multiple cortical areas. This time resolution is crucial for understanding the information neurons encode, their dynamics during behavior, and their connectivity. A community of scientists across the US and the globe will be cultivated to disseminate the research, aid in its implementation, and accelerate collaborative progress in neuroscience. Workshops will also be held to train scientists in advanced optics and neuroscience. Ultimately, this project will provide new technology that is crucial for the BRAIN Initiative, and will foster a broader scientific community for further progress in the field of two-photon imaging.

The research team will develop a two photon (2p) imaging system with a wide field-of-view (FOV) (~ 3 mm) and cellular resolution across the full FOV. To ensure high temporal resolution of recorded activity, they will also develop multiplexed beams that image brain regions within the FOV at high speed. These multiplexed beams can be dynamically reconfigured to target different areas within the full FOV, like spotlights. The approach is to model the full system and create optimized optical subassemblies, including a custom objective. The team will make calculated engineering tradeoffs to preserve cellular resolution while still achieving a wide FOV. High speed scanning will be developed using resonant scanners and photon counting electronics. This system is scalable, as the beam multiplexing can be modularized, and multiple modules can be stacked to increase the number of beams, so long as the fluorescence lifetime is shorter than the interval between laser pulses. Thus, the Trepan2p (Twin-Region, Panoramic 2p), will enable direct measurements of cross-correlations and moment-to-moment, dynamics in extended brain networks. This technology will enable previously impossible experiments, imaging neuronal activity with single cell resolution across extended neuronal circuitry in an array of model systems including mice and primates.