Background: The past and future of extracellular recording (hardware and software)

Extracellular recording is a method for monitoring the electrical activity of individual neurons in vivo. The devices used for these recordings are improving rapidly and have now progressed well beyond the traditional "single-wire" metal electrode. Microfabrication techniques are now used to create silicon devices (polytrodes) with >32 individual electrodes on a shaft, and the pending application of CMOS technology (NeuroSeeker) promises to greatly expand the number of discrete recording sites.

The NeuroSeeker consortium is developing CMOS-based neural electrodes with thousands of individual channels.

The NeuroSeeker consortium is developing CMOS-based neural electrodes with thousands of individual channels.

However, the analysis-methods for interpreting the data gathered by these increasingly dense recording probes must be improved (or new methods invented!). Therefore, to help encourage the development of new analysis strategies for the data gathered by these ultra-dense neural polytrodes, we at the Kampff Lab are gathering a "ground-truth" dataset that can be used to validate both the performance of these new electrode devices and the software tools developed to interpret their data.

"Ground-Truth" data from silicon polytrodes

To gather validation data, for which we know when a neuron nearby the extracellular probe is active, we developed a technique for "paired recordings" (manuscript draft). We use high accuracy, optically-calibrated mechanical manipulators to position two probes, the extracellular device and a glass micro-pipette capable of isolating a single neuron, at the same location in the brain.

Paired-recordings from the intact brain.

Paired-recordings from the intact brain.

The signals recorded with both probes can then be used to cross-validate one another. The pipette (juxtacellular) recording tells us exactly when one neuron is active and the challenge is to detect and isolate (i.e. "sort") this neuron's signal from all of the others seen by the extracellular polytrode. Data from these recordings can be obtained below. A summary of the current (and ever expanding dataset) is available here. Good luck!


Polytrode (32 and 128 Channel) and Juxtacellular Paired Recordings


Acknowledgements

This project and dataset was made possible thanks to generous support from European Union’s Seventh Framework Programme (FP7/2007-2013) under grant agreement nr. 600925, the FCT-MCTES doctoral grants SFRH/BD/76004/2011 given to Joana Neto, and the Bial Foundation (Grant 190/12). Institutional support and funding was provided by the Champalimaud Foundation and the Sainsbury Wellcome Centre (funded by the Gatsby Charitable Foundation and the Wellcome Trust).