Imaging deep inside the brain while an animal is freely behaving can help us discover links between neuronal activity patterns and specific behaviors. For this, miniaturized versions of fluorescence microscopes were developed to record functional calcium dynamics without impeding an animal’s movement. Deeper brain regions are imaged by relaying the optical signal through an implanted GRIN lens, thus bypassing the otherwise prohibitive scattering inside the opaque brain tissue. Yet the cost of making these ‘miniscopes’ incredibly light in order to be head-mountable means compromising on spatial resolution, image quality, optical sectioning and multispectral imaging flexibility.
Conveniently, the implanted GRIN lens can be used to grant other microscopes access to the same field of view imaged by the miniscope. By head-fixing an animal atop a custom-built treadmill, we can visualize the previously imaged brain region with the precision of a laser scanning microscope. Using the multiplexed imaging modes of ZEISS Airyscan 2 detection we can record high-resolution multi-color volumetric data of the entire transfected brain region, as well as record visible calcium activity over extended periods of time. Taken together, this enables us to identify the visibly active neurons and distinguish which cells express one or more fluorescent labels. By co-registering these high-resolution images with the functional imaging during free behavior we can add complimentary information from secondary color channels, adding critical information about the cells that were active during behavior and creating a richer, more nuanced dataset.
In this presentation, we will explore imaging a head-fixed mouse through an implanted GRIN lens using a ZEISS LSM 980 Airyscan 2 microscope, and correlating the high-resolution multicolor images with the original behavioral dataset from the miniscope.