Fast varifocal two-photon microendoscope for imaging neuronal activity in the deep brain

Area of Science:

• Neuroscience
• Biomedical Engineering
• Optical Imaging

Background:

• Fluorescence microendoscopy offers deep brain imaging capabilities.
• Current methods are limited to single focal planes, hindering 3D neural circuit analysis.
• Efficient visualization of neuronal networks is crucial for understanding brain function.

Purpose of the Study:

• To introduce a novel fast varifocal two-photon microendoscope system.
• To enable quasi-simultaneous imaging of neural activity across multiple focal planes.
• To overcome limitations of single-plane imaging in deep brain structures.

Main Methods:

• Utilized a gradient refractive index (GRIN) lens and an electrically tunable lens (ETL).
• Developed a varifocal system for rapid adjustment of imaging depth.
• Implemented two-photon microscopy for enhanced resolution and penetration.

Main Results:

• Achieved quasi-simultaneous imaging at multiple focal planes (85-120 µm separation).
• Operated at fast scan rates of 7.5-15 frames per second per plane.
• Successfully demonstrated in vivo calcium imaging in mouse hippocampus and amygdala.

Conclusions:

• The novel microendoscope system significantly enhances experimental efficiency for deep brain imaging.
• Enables exploration of three-dimensional functional neural circuit architectures.
• Represents a significant advancement for in vivo neuroscience research.