BME PhD Prospectus Defense - Jingwen Deng

Title: "Title: Light-sheet Targeted Illumination Confocal Endomicroscopy for Ultra-fast, Large-scale Imaging of Neurons at Arbitrary Depths"

Advisory Committee: Jerome Mertz, PhD – BU BME (Advisor) Irving Bigio, PhD – BU BME, ECE, Physics, Medicine (Chair) Xue Han, PhD – BU BME Marc A. Sommer, PhD – Duke BME

Abstract: Performing large-scale Calcium and voltage imaging with single neuron resolution at arbitrary locations in the brain has long been a coveted goal of neuroimaging. Light-sheet targeted illumination confocal endomicroscopy offers a promising approach, as it minimizes background fluorescence generation with patterned illumination, rejects out-of-focus fluorescence with confocal detection, enables optical sectioning with nanoengineered beveled fiber bundle probes, eliminates autofluorescence by decoupling the detection path. By integrating these advantages, such an instrument aims to record neural activity in any brain regions with high signal-to-noise ratio (SNR), high signal-to-background ratio (SBR), and high fidelity. To this end, following specific aims are proposed: Aim 1: Improvements of kilohertz targeted illumination confocal microscopy. I am constructing a kilohertz line-scan confocal microscope with targeted illumination. Incorporating a spatial light modulator with near-perfect reflectivity to the pattern generation module maximizes light utilization efficiency. The system flexibly decouples the detection path from the illumination path, preventing fiber autofluorescence contamination. Optical photon reassignment is integrated into the scanning module to enhance spatial resolution and light detection efficiency. Aim 2 : Engineering the optical properties of beveled fiber bundles. Due to refraction, the light emission geometry of beveled fiber bundles is bent to form a light-sheet, obtaining optical sectioning capability. I propose to print a metasurface directly onto the fiber to selectively correct the fluorescence collection geometry perpendicular to the bevel surface. Low risk alternatives include: (1) expanding fiber illumination and collection numerical aperture (NA) with a diffraction grating or a diffusing surface; (2) enhancing fiber power transmission efficiency with an anti-reflection coating; (3) reducing light bending using a polymer fiber bundle. Aim 3 : Examining Calcium and Voltage activities of striatal neurons during movement. Beveled fiber bundle probes will be implanted to enable simultaneous observation of the striatal neuron activities across the entire dorsal-ventral span. A large imaging field of view (FOV) permits assessment of the correlative relationships between striatal neurons and the involvement of different striatal subregions during different movement states. Voltage imaging at kilohertz frame rate grants access to spiking patterns and subthreshold dynamics of striatal neurons. Different striatal cell types, such as Parvalbumin (PV) and cholinergic interneurons (CHIs), will be labeled for the investigation of their distinct contributions to movement regulation.