# Optical imaging of neural activity based on the Lorentz effect

> **NIH NIH R21** · UNIVERSITY OF MINNESOTA · 2020 · $399,211

## Abstract

PROJECT SUMMARY / ABSTRACT
The development of label-free imaging technologies that directly assess neural activity remains a pressing
need. Among a variety of techniques that aim to detect transient signals associated with action potential
(AP) propagation, optical techniques have the potential for revealing and locating APs with high spatio-
temporal resolution. For instance, differential-phase interferometry and then phase-sensitive
measurements of spectral-domain optical coherence tomography (OCT) have allowed us to detect AP-
related nanometer-scale transient structural changes from unmyelinated invertebrate axons. To obtain
useful tests of nerve function, however, investigations on contrast enhancement methods for both
myelinated and unmyelinated nerve fibers are needed. The long term goal of this project is to provide non-
contact depth-resolved optical measurements of nerve function that are useful in basic scientific research.
The overall objective of this project is to use multi-contrast OCT and contrast enhancement methods for
depth-resolved label-free imaging of neural activity in myelinated and unmyelinated nerve models. The
hypothesis behind the work is that a properly directed external static magnetic field generates Lorentz force
in functioning nerve (due to ionic movements / action currents), which consequently induces a mechanical
wave accompanying AP propagation and facilitates the optical imaging of neural activity. Phase-sensitive
OCT is well poised to locate such transient signals with sub-nanometer sensitivity. We will also monitor the
intensity (reflectivity) and birefringence (retardance) signals as additional indications of neural activity. To
achieve the objective of this application, we will pursue optical imaging of neural activity based on Lorentz
effect in ex-vivo preparations (Specific Aim 1) and in-vivo visual cortex (Specific Aim 2). With successful
completion of the proposed work, we will achieve the following outcomes. The feasibility of using Lorentz
effect to aid label-free optical imaging of APs will be revealed. This will also inform people in related
imaging fields to determine whether the Lorentz effect imaging is within the capabilities of current
technology. If our work is shown to be useful, it will support functional neural investigations in laboratory
setting. The results may also suggest more challenging in-vivo applications that require incorporation of
active tracking systems for the needed stability.

## Key facts

- **NIH application ID:** 9977534
- **Project number:** 1R21NS112413-01A1
- **Recipient organization:** UNIVERSITY OF MINNESOTA
- **Principal Investigator:** TANER AKKIN
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $399,211
- **Award type:** 1
- **Project period:** 2020-04-01 → 2024-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9977534

## Citation

> US National Institutes of Health, RePORTER application 9977534, Optical imaging of neural activity based on the Lorentz effect (1R21NS112413-01A1). Retrieved via AI Analytics 2026-06-12 from https://api.ai-analytics.org/grant/nih/9977534. Licensed CC0.

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