Axon hillock currents enable single-neuron-resolved 3D reconstruction using diamond nitrogen-vacancy magnetometry

Madhur Parashar,Sharba Bandyopadhyay,Kasturi Saha

doi:10.1038/s42005-020-00439-6

Madhur Parashar, Sharba Bandyopadhyay + Show 1 more

Open Access

https://doi.org/10.1038/s42005-020-00439-6

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Abstract

Sensing neuronal action potential associated magnetic fields (APMFs) is an emerging viable alternative of functional brain mapping. Measurement of APMFs of large axons of worms have been possible due to their size. In the mammalian brain, axon sizes, their numbers and routes, restricts using such functional imaging methods. With a segmented model of mammalian pyramidal neurons, we show that the APMF of intra-axonal currents in the axon hillock are two orders of magnitude larger than other neuronal locations. Expected 2D magnetic field maps of naturalistic spiking activity of a volume of neurons via widefield diamond-nitrogen-vacancy-center-magnetometry were simulated. A dictionary-based matching pursuit type algorithm applied to the data using the axon-hillock’s APMF signature allowed spatiotemporal reconstruction of action potentials in the volume of brain tissue at single cell resolution. Enhancement of APMF signals coupled with magnetometry advances thus can potentially replace current functional brain mapping techniques.

Highlights

Sensing neuronal action potential associated magnetic fields (APMFs) is an emerging viable alternative of functional brain mapping
We address the reconstruction of spike location and timing for realistic mammalian cortical pyramidal neurons, comprising of soma, axon-hillock region, axon initial segment, and other regions, with respect to the case of measuring 2D vector magnetic field map (referred as diamond–nitrogen-vacancy magnetometric maps (NVMM) further in this text) via widefield diamond nitrogen-vacancy centers (NVC) magnetometry
We propose an adaptation of dictionary-based matching pursuit algorithm[36,37,38,39], to be applied on measurements from widefield diamond NVC magnetometry, for solving individual spike timings and locations in a 3D volume of randomly oriented pyramidal neurons

Summary

Introduction

Sensing neuronal action potential associated magnetic fields (APMFs) is an emerging viable alternative of functional brain mapping. We address the reconstruction of spike location and timing for realistic mammalian cortical pyramidal neurons, comprising of soma, axon-hillock region, axon initial segment, and other regions, with respect to the case of measuring 2D vector magnetic field map (referred as diamond–nitrogen-vacancy magnetometric maps (NVMM) further in this text) via widefield diamond NVC magnetometry. We propose an adaptation of dictionary-based matching pursuit algorithm[36,37,38,39], to be applied on measurements from widefield diamond NVC magnetometry, for solving individual spike timings and locations in a 3D volume of randomly oriented pyramidal neurons. We infer that strongly correlated columns of the dictionary, due to the similarity of magnetic field patterns formed by two closely located neurons, are the main constraints to achieving perfect reconstruction

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