Acute Microelectrode Array Assembly

Coming in Summer, 2007 - Cyberkinetics iridium tip microelectrode array for chronic neural stimulation and recording
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The Acute Microelectrode Array Assembly with IDC connectors.

• Penetrating microelectrodes, 1.0 mm or 1.5 mm long.
• Microelectrode spacing = 400 microns.
• Exceptional recording stability.
• Applications in sensory cortex, motor cortex, spinal cord, retinal flat mounts, peripheral nerve fibers, and tissue slices.
• Also capable of stimulation.

Ordering Information Required

1. Length of electrodes: 1.0 mm or 1.5 mm.
2. Total number of electrodes in the array: e.g. 10x10, 5x5
3. Type of connector board: Four IDC-26 connectors (100CONN-02), three Samtec connectors (ICS-96). (PCB holders which are an optional extra.)

Cables from the Connector to the Amplifier

The CONN-02 printed circuit board uses four IDC-26 male connectors. These mate with regular ribbon cables fitted with IDC-26 female connectors. We supply short (13 cm) unshielded ribbon cables or longer (50 cm) shielded ribbon cables (in the latter, the ribbon is curled into a round cable within the shielding).

Which cable should you use? We have found there is no clear answer, except that you will have fewer problems with extraneous noise if you keep the cables as short as possible. You may need to experiment with different cables for your particular environment.

The ICS-96 connector uses Samtec 0.05" pitch FTSH series male connectors. These mate with Samtec micro ribbon cables that we sell in 15 cm and 60 cm length. We recommend that the longer cable is used with headstage followers.

It is important that you do not allow the weight of the amplifier cables to move the PCB and hence the array. You can use conventional laboratory clamping systems or the appropriate acute connector board holder offered by Cyberkinetics.

General Description of Acute Assemblies

The Cyberkinetics acute microelectrode arrays have been developed to allow parallel recording of multi- and single-unit responses from large populations of neurons in anesthetized animals or in-vitro slice or slice-like preparations. The microelectrode arrays have been evaluated in dozens of implantations in feline visual cortex and peripheral nerve, in primate motor cortex, and in the vertebrate retina. The very large surface area of the array of penetrating electrodes, coupled with the array's very thin substrate, provides excellent recording stability.

Arrays are built from high purity monocrystalline silicon and consist of a set of up to 100 sharpened needles that project out from a silicon substrate. Each needle is electrically isolated from neighboring needles by non-conducting glass. The electrode arrays are insulated with Parylene-C polymer, and each needle has an active electrode tip that is coated with pure platinum. The active electrode tips are typically 35-75 microns in length and result in electrode impedances from 100 to 800 kohms. The needles are built on a square grid with a 0.4 mm spacing and they project out from a silicon substrate about 0.25 mm-thick which assures a minimal supercortical profile. The array can be supplied with electrodes 1.0-mm or 1.5-mm long. Connections to all 100 electrodes are brought out to a printed circuit card with 100 insulated 1-mil Au/Pd wires for interfacing to amplifiers with four flexible cables. The standard length of this bundle of wires is 5 cm or 7 cm but customized versions are available.

Cyberkinetics Microelectrode Arrays have a very large surface area that permits excellent, long term recording stability, but the high density electrode spacing makes it difficult to implant the arrays in neural tissues in a conventional manner. Trying to push the array into tissue only mechanically depresses the surface of the tissue, resulting in incomplete insertion of the array and potential tissue trauma. However, the viscoelastic nature of neural tissues make it possible to implant the arrays with a high-velocity insertion technique. Our pneumatically-actuated impulse inserter has been designed to use a momentum transfer technique to insert the 100-electrode arrays into feline and primate cerebral cortical tissues in about 3 ms. This high velocity insertion has been used in scores of array implantations and produces complete insertions of the array with little bleeding and minimal tissue insult. The inserter has a number of variable parameters which allow the user to implant Cyberkinetics Electrode Arrays into a wide variety of neural tissues. The Impulse Inserter is described in a separate product data sheet.

Specifications

Electrodes:

• 96 to 100 electrodes in a 10 by 10 array.
• 1.0 mm or 1.5 mm in length.
• Diameter of electrode at base is approximately 80 µm.
• Radius of electrode tip is approximately 3-5 µm.
• Active electrode region is platinum, 35-75 µm long.
• Electrode impedance is approximately 100-800 kOhm.
• Substrate and needles insulated with parylene insulation.
• Substrate is 4.2 mm x 4.2 mm x 0.25 mm silicon.

Lead Wires:

• Insulated, 1 mil diameter Au/Pd wires bonded to each of the 100 electrodes.
• Lead wires are bonded to bond pads on the rear surface of substrate, and potted with silicone elastomer.
• Printed Wiring Board Connector. (Conn-02 or ICS-96 Type)
• Four 26-pin 2.5mm pitch ribbon cable connectors, or three 40-pin 0.05" pitch micro ribbon cables.

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Coming Soon in Summer, 2007

Cyberkinetics iridium tip microelectrode array for chronic neural stimulation & recording - Cortical long term microstimulation has the potential to revolutionize the field of neuroprostheses. Electrical stimulation of various cortical regions has been employed for many years for purposes ranging from mapping of brain regions to manipulating behavioral decisions. Initial studies of surface electrical stimulation involved activating large regions of the brain in order to test perception in sensory areas and gross movement in motor regions. However, the field of intra-cortical microstimulation can provide an understanding of the underlying effects of forcing current into the brain beyond activating very large volumes of neurons surrounding the electrode site.

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