Large-volume and deep brain imaging in rabbits and monkeys using COMPACT two-photon microscopy

Area of Science:

• Neuroscience
• Biomedical Engineering
• Optical Imaging

Background:

• In vivo imaging is crucial for understanding neural structure and function, typically limited to ~800 μm depth.
• Light scattering and absorption hinder two-photon microscopy for imaging deep cortical and subcortical neurons in large animals.

Purpose of the Study:

• To develop an advanced in vivo imaging method for deep brain structures in large animals.
• To enable large-volume structural and calcium imaging of neurons located up to 2 mm below the brain surface.

Main Methods:

• Combined a thin-wall quartz capillary with a GRIN lens and prism for deep brain imaging.
• Expanded the field of view by rotating and adjusting the imaging probe's depth within the quartz capillary.
• Utilized two-photon microscopy for structural and calcium imaging in rabbit and monkey brains.

Main Results:

• Successfully imaged neurons located 2 mm below the surface of rabbit and monkey brains.
• Demonstrated differential activity of layer 5/6 neurons in the rabbit motor cortex during quiet wakefulness and slow-wave sleep.
• Achieved large-volume imaging by manipulating the probe's position within the capillary.

Conclusions:

• The developed method overcomes limitations of traditional two-photon microscopy for deep brain imaging in large animals.
• Provides a valuable tool for investigating the structure and function of deep neurons.
• Enables new research avenues into the neural basis of complex behaviors and states in deep brain regions.