Miniaturized fluorescence microscopes are becoming more important for deciphering the neural codes underlying various brain functions. Using gradient index (GRIN) lenses, these devices enable the recording of neuronal activity in deep brain structures. However, to minimize any damage to brain tissue and local circuits, the diameter of the GRIN lens should be 0.5-1 mm, which results in a small field of view. Considering the three-dimensional (3D) structure of neural circuits in the brain, volumetric imaging capability would increase the number of neurons imaged through the lenses. To observe 3D calcium dynamics, we developed a miniaturized microscope with an electrically tunable lens. Using this microscope, we performed 3D calcium imaging in behaving mice and were able to image approximately twice the number of cells as could be recorded using a 2D imaging technique. This simple low-cost 3D microscope will improve the efficiency of calcium imaging in behaving animals.
bioRxiv Subject Collection: Neuroscience