Abstract
The advent of multi-sensor microelectrodes for extracellular action potential recordings has significantly improved the quality of recorded signals, allowing more reliable detection and classification of action potentials recorded in vivo. These microelectrodes can also be used to localize neuronal signal sources, which may allow experimentalists to estimate other parameters including the neurons’ migration trends, intensities and sizes. This information can also be used to resolve neurons based on their location and type. However, as the exact characteristics of neurons are unknown during in vivo experiments, current attempts to localize neuronal signal sources have not been validated. This article presents experimental validation of a method capable of estimating both the location and intensity of an electrical source. To this end, a stimulating electrode was immersed in a saline solution and its stimulus patterns were recorded by a commercially available four-sensor microelectrode (tetrode). The location of the tetrode was varied with respect to the stimulator, and for each tetrode position, the stimulus was generated at multiple intensity levels. The location and intensity of the source were estimated using the Multiple Signal Classification (MUSIC) algorithm, and the results were quantified by comparison to the parameters’ true values. Localization results, with an accuracy and precision of ~10 μm, and ~11 μm respectively, imply the method’s ability to resolve individual neuronal sources. Similarly, source intensity estimation results indicate that this approach can accurately track changes in neuronal signal amplitude. Together, these results demonstrate the potential of the presented approach in characterizing neuronal signal sources in vivo, which may significantly improve the extracellular recording process and enable a more accurate interpretation of experimental data.
Highlights
Two decades ago, a handful of researchers began discussing an intriguing idea: Could the equipment needed for everyday chemistry and biology procedures possibly be shrunk to fit on a chip the size of a fingernail? Miniature devices for, say, analyzing DNA and proteins should be faster and cheaper than conventional versions
For an infinite half-space, the diffraction angle is only given by the ratio of the sound velocities in the substrate and in the fluid, respectively, and can be understood as a consequence of phase matching between the surface acoustic wave (SAW) and the radiated sound beam in the liquid
Our SAW driven, freely programmable lab-on-a-chip system allows for the isolation and transfer of smallest amounts of genetic material on a micro scale precision
Summary
Two decades ago, a handful of researchers began discussing an intriguing idea: Could the equipment needed for everyday chemistry and biology procedures possibly be shrunk to fit on a chip the size of a fingernail? Miniature devices for, say, analyzing DNA and proteins should be faster and cheaper than conventional versions. The ability to precisely control various parameters such as the choice of substrate, flow rate, buffer composition and surface chemistry in these micro scale devices, makes them ideal for a broad spectrum of cell-biology-based applications. It has a high sensitivity for mass loading and (di) electrical changes of the surface environment by still maintaining the ability to operate in liquids with minimal propagation loss [26].
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