FAQ

Questions and Answers on Multichannel Interfaces to the Central and Peripheral Nervous

Arrays

Q. Can you make longer or shorter electrodes?
A. Our standard electrode lengths are 1 mm and 1.5 mm.

Q. What are the impedances of the electrodes?
A. The impedances are measured with a 1 kHz, sine wave with 100 nA current and are typically in the range of 100 kOhms to 800 kOhms.

Q. These impedances seem rather low.
A. The position of the electrode array is fixed once it is implanted. Our electrodes have a relatively large active area that increases the likelihood that the active electrode area will be able to record activity from functioning neurons.

Q. How large are the electrode tips?
A. The average tip length is about 50 µm; the size varies from 30 µm to 70 µm. The tip radius is approximately 1-4 µm.

Q. Can you make arrays of different shapes?
A. We can make arrays of a variety of shapes from the standard 10x10, such as 2x10 and 5x5.

Q. Can I reuse the arrays?
A. You can use an acute array many times provided you clean it well between uses. The chronic arrays cannot be reused as they are generally integrated into the skull and the lead wires are coated with silastomer.

Q. How do I clean the arrays?
A. The acute array can be cleaned using a artist's fine paint brush - 4 to 5 mm diameter - with the bristles trimmed to a length of 5 mm. After the array is explanted, place it immediately in saline or distilled water and gently remove any remnant material on the array with the brush. Mechanical cleaning is best when combined with a deproteinizing detergent. Rinse the array thoroughly after this process. Do not use an ultrasonic bath.

Q. How are the electrodes insulated?
A. We use Parylene C to insulate the electrodes. The thickness is approximately 3µm .

Q. How many of the electrodes pick up useful signals?
A. This varies from preparation to preparation and depends to some extent on the technique of the experimenter. In our best implants, more than 90% of the electrodes have useful signals.

Connectors

Q. How can I minimize the lead wire tethering forces?
A. In our experiments, we generally put strain relief kinks in the lead wires to help mitigate the problem of tethering forces.

Q. How do you sterilize the arrays?
A. Arrays can be either gas-sterilized or autoclaved.

Q. What type of wire is used from the array to the connector?
A. We generally use 1-mil gold wire insulated with Isonel / Polyester.

Implantation

Q. Why do you need to implant the arrays with the special inserter?
A. We have tried a variety of implantation technologies and found the high-velocity impulse insertion technique to be the most effective. Simply pushing the electrode into the cortex results in an incomplete implantation of the array. We have used our pneumatically actuated impulse array successfully in many implantations.

Q. Do you implant it through the dura?
A. We have limited experience implanting the array through the dura in rat barrel cortex. However, we do not generally recommend this procedure in higher mammalian species with thicker dura, because it can result in breakage of electrodes or subdural hematomas.

Q. Can I partially implant the array so I can adjust the penetration depth?
A. Yes. In acute experiments, the depth can be set for partial insertion with various spacers on the inserter wand.

Q. How do you hold the array in place?
A. After we have made an opening over the implant site we bolt the pedestal to the animal's skull. The pedestal is designed to use 2.0 mm diameter titanium surgical screws. We bend the lead wires in an appropriate fashion so that the array sits over the implant site with no net stress on the lead wires. The dura is reflected and the array is repositioned. We once again make sure that the electrode array and wires relax in the position of the implant and then position the pneumatic implanter over the array and insert it.

Q. How much tissue damage occurs during insertion?
A. There is minimal tissue damage when the insertion procedure is followed carefully. However, sub-pial bleeding may occur if the device is not positioned appropriately over the array during insertion.

Q. How do you perform the surgery for chronic and acute implantations?
A. Details of the surgical techniques are printed in the implantation manual included with our inserter.

Q. How do you sterilize the inserter?
A. The inserter wand, the electronic trigger switch, and the air-lines can be gas sterilized. The inserter wand can also be steam sterilized.

Amplifiers

Q. Do I need headstage pre-amplifiers?
A. The electrode array impedance is sufficiently low that is not a requirement. Signal-to-noise ratios are adequate without pre-amps. In chronic experiments with free moving animals, a headstage is recommended due to capacitive noise that can be generated as the animal moves.

Q. What is the cross-talk between channels like?
A. The amplifiers have virtually no measurable cross-talk between channels.

Q. What is the noise level of your amplifiers?
A. The equivalent input noise on the amplifiers is about 3 µV RMS. However, when this is viewed on an oscilloscope, the peak-to-peak noise of the amplifier is about 12 µV.

Neural Signal Processor

Q. Can I use the Cerebus™ system with my current PC?
A. Yes. However, we recommend that you verify that the PC meets the minimum specifications for the Cerebus™ system. You may contact the Cyberkinetics lab for the recommended PC specifications.

Q. Can I use the Cerebus™ system with electrodes from other vendors?
A. Yes.

Software

Q. Does the data acquisition software work on-line / real time?
A. The acquisition software has on-line / real time and off-line time spike classification capability and the ability to stream the data for real time analysis.

Q. What is the speed of the data capture?
A. We acquire data at 30,000 samples / sec / electrode.

Q. Can you sort the signals?
A. Spike sorting is done on-line with our custom-made software that applies a choice of manual spike sorting or automatic on-line sorting from each electrode to identify different neurons. In addition, we have off-line automated spike sorting tools.

Q. What operating systems does your software use?
A. The data acquisition and classification programs run with Windows 2000, Windows XP, and Windows Vista.

Uses

Q. What animals have been implanted with Cyberkinetics arrays?
A. Experiments have been successfully conducted in monkey visual and motor cortex, cat visual and auditory cortex, rat sciatic nerve, olfactory bulb, and barrel cortex, cat sciatic nerve.

Q. Can I use the arrays for slices of neural tissue?
A. We have conducted experiments in isolated turtle and rabbit retinal preparations and have recorded from as many as 60% of the 100 electrodes with excellent signal-to-noise ratios.

Q. How long have you had the arrays implanted in animals?
A. Over three years in primates, two years in cats (the animals were perfused for histological studies).

Q. Can you use the array systems for stimulation?
A. With the current array with pure platinum active tips, we have stimulated sciatic nerve in acute experiments and obtained twitches in the distal musculature with stimulation in the 1 to 500 µA range. Behavioral responses were evoked when a 1 to 10 µA current was passed in cat auditory cortex. Coming summer 2007, Cyberkinetics will launch a chronic long term stimulation / recording array option to researchers with Iridium active tips. The platinum tipped arrays also work well for acute stimulation experiments.

Q. How much attenuation of the signals occurs via the cables?
A. Attenuation of the signals occurs due to the distributed capacitance of the shielded cables that connect the animal to the amplifier. This amounts to about 3.5%/foot of cable. For example, a two-foot cable will produce about 7% attenuation.

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