Local Rigidity and Soft Release for Improved ECoG Arrays
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1
University of Bremen, Brain Research Institute, Germany
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2
University of Bremen, IMSAS Institute, Germany
The electrocorticogram (ECoG) recorded at the surface of the brain is considered a promising source of signals for neuroprosthetics and related medical applications. Here we present a novel design and fabrication process for an ECoG-recording array, and the first measurements in a macaque monkey. The array consists of three regions: a flexible recording area, a 4-cm-long flexible cable, and a polyimide-over-silicon (PI/SiO2/Si) area on top of which four 32-pin NPD Omnetics connectors were bonded with conductive glue. The flexible components are meant to adapt to the irregular surface of the brain. Furthermore, the entire structure is a free-standing membrane, attached by removable polyimide straps to its carrier substrate.
The recording area of the device is a regular hexagon with a side length of 7.2 mm. It consists of two 5-µm-thick PI films enclosing 124 gold electrode sites, each 300-nm thick. The electrode sites have three different diameters (0.1—0.5 mm) and the inter-electrode spacing throughout the array varies between three specific pitch values (0.8—2.2 mm). The purpose of this unique design is to compare signal quality across electrode sizes and distances with a single array and relatively close cortical locations in a single animal. A large area of sputtered Au enclosed by a strip of PI separate from the main working area acts as the reference electrode, which is then bent and fixed to the backside of the array, with the gold side facing towards the skull. The gold layer is partially perforated for increased flexibility and a means to control the propagation of stress-induced cracks in the metal.
The novel design and fabrication process offers three significant advantages: (1) handling of the device is made safer and easier by relying on the rigid substrate; (2) standard soldering techniques can be utilized more comfortably thanks to the Si layer underneath the connector area; and (3) direct manipulation of the array is not necessary for soldering and testing, which reduces the risk of damage and contamination before implantation. The device was implanted epidurally on the primary visual cortex (V1) of a Rhesus macaque (Macaca mulatta) and it has been used successfully to record local field potentials. The data obtained from this array will be used to decide on the most suitable electrode size and inter-electrode distance for a “second-generation” array, which is intended to become part of a fully wireless chronic neural recording microelectronic system.
Keywords:
electrocorticogram,
Electrode array design,
Electrode array fabrication,
Multichannel recording,
Rhesus Monkey
Conference:
BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011, Freiburg, Germany, 4 Oct - 6 Oct, 2011.
Presentation Type:
Poster
Topic:
neurotechnology and brain-machine interface (please use "neurotechnology and brain-machine interface" as keyword)
Citation:
Gordillo Gonzalez
VA,
Tolstosheeva
E,
Hertzberg
T,
Mandon
S,
Kreiter
AK and
Lang
W
(2011). Local Rigidity and Soft Release for Improved ECoG Arrays.
Front. Comput. Neurosci.
Conference Abstract:
BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011.
doi: 10.3389/conf.fncom.2011.53.00118
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Received:
23 Aug 2011;
Published Online:
04 Oct 2011.
*
Correspondence:
Prof. Walter Lang, University of Bremen, IMSAS Institute, Bremen, 28359, Germany, wlang@imsas.uni-bremen.de