Multi-fiber array-based photometry system for multi-regional functional mapping in the mouse brain

Abstract Mesoscopic functional brain mapping is essential to better understanding of various brain functions and dysfunctions. However, accessing distributed neural circuits in mammalian brain regions remains a significant challenge. While fiber photometry is a versatile optical approach, existing methods often suffer from invasiveness and scalability. Here we present an affordable multi-fiber array (MFA)-based photometry system to monitor neural signals across multiple regions. Our system comprises a custom-designed MFA utilizing 50-µm diameter optical fibers and off-the-shelf optical components. To demonstrate the system’s versatility, we monitored GABAergic population activity using jGCaMP8s across multiple brain regions in head-fixed, awake mice. By combining with pupillometry, we identified state-dependent, region-specific GABAergic dynamics. Our MFA-based photometry system opens new avenues for investigating state-dependent neural dynamics at the mesoscopic level. To facilitate wider adoption, all codes and resources are publicly available on GitHub (https://github.com/Sakata-Lab/MFA). Competing Interest Statement The authors have declared no competing interest.