Functional Ultrasound Localization Microscopy on Freely Moving Rats

Area of Science:

• Neuroscience
• Biomedical Engineering
• Medical Imaging

Background:

• Brain-wide functional neuroimaging at single-vessel resolution in freely moving animals is challenging.
• Functional ultrasound localization microscopy (fULM) provides high-resolution hemodynamic imaging but is typically limited to head-fixed preparations.

Purpose of the Study:

• To develop and validate a platform for fULM in freely moving rats.
• To enable high-resolution, brain-wide hemodynamic imaging under naturalistic behavioral conditions.

Main Methods:

• Integration of a magnetic probe-clamping interface, a pulley-based tether, and chronic jugular venous access.
• Development of a motion-correction processing pipeline for freely moving ULM data.
• Utilized visual stimulation and pharmacological agents (SR-17018) to probe brain responses.

Main Results:

• The platform reliably captured functional hemodynamic responses and enabled super-resolved vascular reconstruction in deep brain regions.
• Freely moving fULM resolved stimulus-evoked, vessel-specific changes in diameter and flow velocity.
• Observed transient, region-dependent cerebrovascular responses to an opioid agonist, with significant flow-velocity changes.

Conclusions:

• Freely moving fULM is established as a practical platform for whole-brain microvascular imaging in naturalistic behavioral settings.
• This technology reveals microvascular heterogeneity not detectable by conventional methods.
• Enables advanced research into brain function and pharmacology in behaving animals.