Multicore Fiber Bundles for Neuroscience

The goal of this research project is to develop an improved method of delivering light to the brain for imaging and stimulating brain activity. Light is a powerful tool for probing the structure and function of the brain and can be used to image fluorescence signals which indicate the firing of neurons or directly activate neurons using optogenetics. Unfortunately, biological tissue is highly optically scattering due to its varied optical properties. This prevents light from being tightly focused to a specific volume, directly reducing the fidelity of light-based techniques for investigating the brain. In the past several years, optical wavefront shaping techniques have been developed to enable deeper penetration in the brain by reclaiming the scattered photons normally discarded as noise. However, these techniques are stymied because it is challenging to deliver the shaped light to the brain.

This project addresses this challenge by developing a new system which leverages fiber bundles and optical wavefront shaping to reliably deliver shaped light to the brain, even when the fiber bundle is moving. The research goals of this project will provide another tool for neuroscientists to deliver shaped light to the brain, enabling better experiments in the research laboratory and paving the way for clinical applications. The broader impacts of the project include research opportunities for undergraduate students at Harvey Mudd, providing tightly integrated educational opportunities in scientific research methods, optical system design, and neurophotonics. In addition, the PI will develop new educational resources to broaden access to optics through wavefront shaping simulations in Python-based Jupyter notebooks and low-cost lab experiments exploring optical fibers and light matter interactions in scattering media.

Multicore fibers offer an attractive way to deliver light to regions of interest in the brain but are challenging to use in practical applications due to core-dependent phase delays which are impacted by a variety of physical and environmental factors such as movement and temperature fluctuations. The project will address this challenge by developing methods to correct the phase distortion of the multicore fiber without requiring access to the distal end, enabling shaped wavefronts to be flexibly delivered into deep tissue even when the core-to-core phase delays are dynamically changing. The research plan is divided into two major tasks:

  1. Developing a low-coherence interferometry system to measure the phase distortion of the multicore fiber and characterizing key performance metrics such as temporal response and phase sensitivity and
  2. Using the low-coherence interferometry system with wavefront shaping to correct for the phase delay in the multicore fiber and create desired wavefronts (e.g., to form a focus) beyond the distal tip of the fiber.

Acknowledgements

This project is supported by the National Science Foundation via Award #2302023.