In vivo validation of the electronic depth control probes.

In this article, we evaluated the electrophysiological performance of a novel, high-complexity silicon probe array. This brain-implantable probe implements a dynamically reconfigurable voltage-recording device, coordinating large numbers of electronically switchable recording sites, referred to as electronic depth control (EDC). Our results show the potential of the EDC devices to record good-quality local field potentials, and single- and multiple-unit activities in cortical regions during pharmacologically induced cortical slow wave activity in an animal model.

Influence of bio-coatings on the recording performance of neural electrodes.

Neural probes are complex devices consisting of metallic (often Pt based) electrodes, spread over an insolating/dielectric backbone. Their functionality is often limited in time because of the formation of scaring tissues around the implantation tracks. Functionalization of the probes surface can be used to limit the glial scar reaction. This is however challenging, as this treatment has to be equally efficient on all probe surfaces (metallic as well as dielectric) and should not influence the electrodes performances. This paper presents a novel technique to functionalize recording neural probes with hyaluronic acid (HyA), a major component of the extracellular matrix (ECM). HyA and the probe surface are both modified to make the reaction feasible: HyA is chemically functionalized with SS-pyridine groups while the probe surfaces are silanized. The thiol groups thus introduced on the probe surface can then react with the HyA SS-pyridine group, resulting in a covalent bonding of the latter on the former. The electrodes are protected by introducing a pretreatment step, namely an additional hyaluronic acid layer on the platinum electrode, prior to the silanization process, which was found to be effective in reducing electrode impedance under optimized conditions.

Control and data acquisition software for high-density CMOS-based microprobe arrays implementing electronic depth control.

This paper presents the NeuroSelect software for managing the electronic depth control of cerebral CMOS-based microprobes for extracellular in vivo recordings. These microprobes contain up to 500 electronically switchable electrodes which can be appropriately selected with regard to specific neuron locations in the course of a recording experiment. NeuroSelect makes it possible to scan the electrodes electronically and to (re)select those electrodes of best signal quality resulting in a closed-loop design of a neural acquisition system. The signal quality is calculated by the relative power of the spikes compared with the background noise. The spikes are detected by an adaptive threshold using a robust estimator of the standard deviation. Electrodes can be selected in a manual or semi-automatic mode based on the signal quality. This electronic depth control constitutes a significant improvement for multielectrode probes, given that so far the only alternative has been the fine positioning by mechanical probe translation. In addition to managing communication with the hardware controller of the probe array, the software also controls acquisition, processing, display and storage of the neural signals for further analysis.

The NeuroProbes project: a concept for electronic depth control.

The European project NeuroProbes has introduced a new methodology to allow the fine positioning of electrodes within an implantable probe with respect to individual neurons. In this approach, probes are built with a very large number of electrodes which are electronically selectable. This feature is implemented thanks to the modular approach adopted in NeuroProbes, which will allow the implementation of integrated electronics both along the probe shaft and on the array backbone.

The NeuroProbes Project.

Despite the significant progress in recent years in neural recording and stimulation using silicon-based probes, there is still a lack of suitable tools for the truly three-dimensional access to large ensembles of neurons over long periods of time. The objective of the NeuroProbes project is to address such needs and to extend probe capabilities by adopting a modular and scalable approach in which chemical sensing and drug delivery are also incorporated in the same probe system.