Adaptive multi-electrode positioning (AMEP) system for chronic extracellular recording in awake behaving primates
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1
Thomas Recording GmbH, Germany
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2
German Primate Center, Cognitive Neuroscience, Germany
Intra-cortical brain machine interfaces usually use implantable electrode arrays with fixed-geometry. The drawback of these devices is that electrode position cannot be adjusted for signal optimization in chronic preparations. Other implantable and adjustable electrode systems allow to only push the electrodes in one direction, or can not dealt with multiple electrodes. Here we present an adaptive multi-electrode positioning (AMEP) system for chronic implantation and motorized bi-directional electrode adjustments.
The AMEP fits into a standard implantable recording cham¬ber for rhesus monkeys. The system consists of a stainless-steel chamber insert that is introduced into the implanted chamber above the intact dura. It can currently hold 16 individual glass-insulated single-core microelectrodes. Electrodes can be preloaded before insertion of the system into the chamber, but can also be individually replaced on demand, without removing the insert from the chamber. Each of the 16 microelectrodes can be moved independently in its own stainless steel guide tube with 10 mm total travel distance. The rear end of the microelectrode is mechanically interfaced to a micro gripper, which couples to the microelectrode via software control. The gripper is positioned by a motorized and computer-controlled xyz-micromanipulator, which allows it to actuate each of the 16 electrode individually and to movement electrodes in both directions of the z-axis. The bottom of the chamber insert is sealed with a silicone sheet that prevents fluids from entering the electrode guide tubes and improves the mechanical stability of the electrode recording position. The metal-shielded insert houses a 16-channel low-noise preamplifier which makes the system robust against EM-noise.
In summary, the AMEP system is designed to fulfill the following specifications: 1) use of quartz glass insulated platinum tungsten microelectrodes, which are well suited for chronic recording applications, 2) use of a secure electromechanical connection between microelectrodes and preamplifier input to guarantee a low noise signal transmission, 3) good biomechanical compatibility of the microelectrodes, which reduces the risk of gliosis around the electrode tip, 4) small electrode spacing for high spatial resolution, 5) electrical shield around the recording electrodes to avoid electrical noise pick-up from the laboratory environment, 6) possibility to reposition the microelectrodes individually with an axial µm-resolution in both directions by using a microprocessor controlled xyz-micromanipulator system with an electrode gripper. In conclusion, the newly developed AMEP will allow precise microelectrode repositioning in chronic preparations with a travel distance suitable for recordings even from non-surface areas in the cerebral cortex of monkeys. The bi-directionality of movement opens the potential to fully automatize the electrode positioning with signal-driven control algorithms.
Keywords:
Adaptive control,
brain-machine interface,
Chronic implants,
Electrophysiology,
Multi-Electrode Array
Conference:
Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012.
Presentation Type:
Poster
Topic:
Neurotechnology and brain-machine interface
Citation:
Hoehl
D,
Thomas
U and
Gail
A
(2012). Adaptive multi-electrode positioning (AMEP) system for chronic extracellular recording in awake behaving primates.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference 2012.
doi: 10.3389/conf.fncom.2012.55.00094
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Received:
11 May 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Dr. Alexander Gail, German Primate Center, Cognitive Neuroscience, Goettingen, 37077, Germany, agail@gwdg.de