Volumetric Functional Ultrasound Imaging in Macaques

Area of Science:

• Neuroscience
• Medical Imaging
• Primate Research

Background:

• Linking brain circuit activity to large-scale functional organization necessitates advanced imaging techniques.
• Existing methods often lack the required combination of high spatial resolution, broad coverage, and single-trial sensitivity for primate studies.

Purpose of the Study:

• To introduce and validate volumetric functional ultrasound imaging (3D-fUS) in behaving macaques.
• To demonstrate 3D-fUS's capability for high spatiotemporal resolution imaging of cortical volumes.
• To establish 3D-fUS as a tool for efficient investigation of distributed cortical dynamics.

Main Methods:

• Development and application of volumetric functional ultrasound imaging (3D-fUS) in behaving macaques.
• Imaging of approximately 1 cm³ cortical volumes with high spatiotemporal resolution (100 × 150 × 150 μm³ voxels, 1.67 Hz).
• Estimation of a functional ultrasound hemodynamic response function (fUS-HRF) for model-based analyses.

Main Results:

• Reliable detection of visually evoked responses at single-trial and single-voxel levels.
• Substantial reduction in experimental time compared to conventional methods.
• Consistent fUS-HRF across subjects, cortical areas, and stimuli, well-approximated by a gamma function, exhibiting faster dynamics than fMRI-HRFs.

Conclusions:

• 3D-fUS is a powerful, fast, and volumetric imaging modality for primate neuroscience.
• The technique provides circuit-level resolution, enabling efficient investigation of brain dynamics.
• 3D-fUS complements existing methods like fMRI by offering faster hemodynamic response characterization.