Until recently, fluorescence microscopy was dominated by large microscope installations, sometimes referred to as the rigs. The observations of neural circuitry in freely moving animals like mice or rats require wearable fluorescence microscope attached to imaging cannulas chronically implanted in their skulls. To make this microscope mice-wearable, the smallest fluorescence microscope body ever was built that easily snaps into chronically implanted imaging cannula via self-centering latching mechanism.
In neuroscience, the fiber photometry denotes a method where the optical fiber(s) chronically implanted near the targeted brain region of interest expressing calcium indicator(s) delivers excitation light and collects overall fluorescence induced by calcium-activity during the light excitation. While the fluorescence microendoscopy records activity of individual neurons within the field of view, the fiber photometry sums up the overall fluorescence of neurons expressing a genetically encoded calcium indicator. The typical setup for freely behaving animals consists of the excitation light source, the beamsplitter/combiner that separates excitation and fluorescence light, the fiber-optic rotary joint, the optical cannula and connecting fiber-optic patch cords.
Single-cell recordings require an optical fiber core diameter at the fiber end comparable with the size of the cell under observation. The electrode tip has to be of the similar size and in close proximity to the fiber core. One way to achieve those specifications is by making a dual core optical fiber having the light guiding core and the capillary within its claddinga b, and pulling or tapering one fiber end into the small diameter tip. When the capillary is filled with electrolyte, the fiber end becomes a usable single-cell opto-electric interface smaller than the cell itself.
The systems that combine optogenetics with electrophysiological recordings open-up new possibilities for neuroscience. They require delivery of appropriate optical signals to the point of interest within the neural tissue and detection and processing of the electrical spikes from neural activity. The system definition starts from the chronically implanted opto-electric cannula for behaving animals or from the opto-electric probes for in-vitro or fixed animal. For behaving animals, there is the tethered and the wireless/fiberless option.