Parallel multi-region adaptive optics module for high-resolution imaging in deep brain microendoscopy.

Gradient refractive index (GRIN) lens-based microendoscopy provides optical access to deep brain regions, but image quality over the field of view (FOV) is often degraded by complex, spatially varying off-axis aberrations that are difficult to correct with conventional adaptive optics over a large FOV. Existing adaptive optics approaches have improved image quality in GRIN-lens-based imaging, but they remain limited in correction speed, imaging speed, and system compatibility. To address these challenges, we developed a parallel multi-region adaptive optics module and integrated it into both one-photon and two-photon microendoscopes, enabling simultaneous aberration correction in nine subregions of a GRIN lens using a spatial light modulator (SLM). By combining multi-focus illumination with parallel multi-region aberration correction, our system adapts to complex spatial aberration variations and achieves near-diffraction-limited imaging over a large FOV, extending the usable field radius from 105 µm to 185 µm from the FOV center (corresponding to an ∼300% area enlargement), while improving both correction efficiency and imaging speed. Validation experiments with fluorescent beads, fixed brain tissue, and in vivo hippocampal CA1 imaging in awake mice demonstrate substantial improvements in both resolution and signal strength, particularly toward the edge of the FOV where aberrations are most severe. This method provides a practical solution for high-resolution, high-speed microendoscopic imaging in deep brain research.