Abstract
Purpose: :
Motivated by the success of cochlear implants for deaf patients, we are now facing the challenge of creating a visual prosthesis, based on a new generation of highly biocompatible and multifunctional 3D intracortical microelectrodes designed to interface with the occipital visual cortex as a means through which a limited, but useful visual sense could be restored in profoundly blind individuals.
Methods: :
We developed in the framework of the European Project NeuroProbes, a new generation of multielectrode arrays (MEA) based on silicon shafts with a cross section of 100 x 120 microns. Basic 2D MEAs were integrated into 3D MEAs using a slim backbone and a modular technology. 4-shaft-combs with 36 electrodes made of smooth platinum, electroplated platinum black or platinum/iridium were implanted in rabbit cerebral cortex. The electrodes were connected to the recording/stimulating equipment using highly flexible polyimide cables. After several time periods the animals were sacrificed and the MEAs were explanted. The implanted site was removed and processed by immunohystochemical techniques.
Results: :
These probes are capable to penetrate into the brain at low insertion speeds without introducing excessive dimpling. We successfully recorded single and multi unit activity as well as LPFs from cortical neurons. Neural recordings taken from the same electrodes before and after multiple electrical stimulation sessions were very similar in signal/noise ratio and in the number of recordable units. The continuous presence of the microelectrodes appears to result in a sustained response, at least partially composed of reactive glia, that maintains a compact sheath which isolates the microelectrodes from the brain.
Conclusions: :
The new NeuroProbes arrays are well tolerated by the central nervous system. Our data suggest that this new generation of MEAs can be used to record and stimulate cortical neurons and could be used for a long-term stable and safe clinical neuroprosthesis. However more studies regarding possible damage of neural tissues by permanent charge injection and the more effective means of stimulating cortical tissue using this new generation of MEAs arrays are needed.
Keywords: visual cortex • electrophysiology: non-clinical • pattern vision