Low-cost reversible tandem lens mesoscope for brain imaging in rodents.

Significance: The development of imaging systems that are cost-efficient and modular is essential for modern neuroscience research.

Aim: In the current study, we designed, developed, and characterized a low-cost reversible tandem lens mesoscope for brain imaging in rodents.

Approach: Using readily available components, we assembled a robust imaging system that is highly efficient and cost-effective. We developed a mesoscope that offers high-resolution structural and functional imaging with cost-effective lenses and CMOS camera.

Results: The reversible tandem lens configuration of the mesoscope offers two fields of view (FOVs), which can be achieved by swapping the objective and imaging lenses. The large FOV configuration of $12.6\times 10.5\mathrm{mm}$ provides a spatial resolution up to $4.92\mu m$, and the small FOV configuration of $6\times 5\mathrm{mm}$ provides a resolution of up to $2.46\mu m$. We demonstrate the efficiency of our system for imaging neuronal calcium activity in both rat and mouse brains in vivo.

Conclusions: The careful selection of the mesoscope components ensured its compactness, portability, and versatility, meaning that different types of samples and sample holders can be easily accommodated, enabling a range of different experiments both in vivo and in vitro. The custom-built reversible FOV mesoscope is cost-effective and was developed for under US$10,000 with excellent performance.