  Multi-sensor microelectrodes for extracellular action potential recording
have significantly improved the quality of in vivo recorded neuronal signals.
These microelectrodes have also been instrumental in the localization of
neuronal signal sources. However, existing neuron localization methods have
been mostly utilized in vivo, where the true neuron location remains unknown.
Therefore, these methods could not be experimentally validated. This article
presents experimental validation of a method capable of estimating both the
location and intensity of an electrical signal source. A four-sensor
microelectrode (tetrode) immersed in a saline solution was used to record
stimulus patterns at multiple intensity levels generated by a stimulating
electrode. The location of the tetrode was varied with respect to the
stimulator. The location and intensity of the stimulator were estimated using
the Multiple Signal Classification (MUSIC) algorithm, and the results were
quantified by comparison to the true values. The localization results, with an
accuracy and precision of ~ 10 microns, and ~ 11 microns respectively, imply
that MUSIC can resolve individual neuronal sources. Similarly, source intensity
estimations indicate that this approach can track changes in signal amplitude
over time. Together, these results suggest that MUSIC can be used to
characterize neuronal signal sources in vivo.
