Name: Surgical Implantation of Chronic Neural Electrodes for Recording Single Unit Activity and Electrocorticographic Signals (Video) | JoVE Journal
Uploaded: 2012-02-24T12:00:00.000+00:00
Duration: 8 min 26 s
Description: Learn surgical implantation of chronic neural electrodes in rodents for electrophysiological recordings. This method enables single unit and electrocorticographic signal acquisition in awake, behaving animals.

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This work was funded by the Center for Neural Communication Technology (CNCT), a P41 Resource Center funded by the National Institute of Biomedical Imaging and Bioengineering (NIBIB, P41 EB002030) and supported by the National Institutes of Health (NIH). The authors wish to thank Rio Vetter of NeuroNexus Technologies for the development of surgical techniques, and Paras Patel of the University of Michigan for compiling the list of equipment used during surgeries.

1. Pre-implant Procedures (Common)
<ol>
 <li>Shave the top of the animal’s head from between the eyes to well behind the ears. Use electric barber’s clippers to shave the head. Scrub head first with isopropyl alcohol, then betadine (repeat 3x). Apply eye lubricant. </li>
 <li>Mount the animal in stereotaxic ear bars. Direct the fixed tip of the right stereotaxic ear bar into the auditory canal of the animal’s right ear by moving the head sideways against the canal. Extreme care must be taken to assure that each ear-bar tip is properly positioned in the auditory meatus. Next, push the loosened left ear bar into the auditory canal and apply slight inward pressure. Grasp the animal’s nose and wiggle it back and forth firmly. If the animal is mounted properly the head will feel rigidly mounted. </li>
</ol>
2. Pre-implantation Surgery (Common)
<ol>
 <li>With a pair of fine scissors, cut two half circles from the midline outwards, partially removing the scalp </li>
 <li> Scrape and remove the periosteum connective tissue that adheres to the bone. Scraping with a blunt edge such as the back of a scalpel blade or the tip of a sterile cotton swab will minimize bleeding because the capillaries will be crushed rather than cut smoothly. Control bone bleeding using bone wax or a cauterizing iron. </li>
 <li>Disinfect and clean the bone surface using hydrogen peroxide. Dry the bone to make the cranial sutures more clearly visible. The Bregma and Lambda points should be noted and used to level the head. The location for craniotomy and electrode implant should be measured with respect to Bregma and can be temporarily marked with a pen or by drilling shallowly into the surface. The craniotomy location will depend on the experimental aims of the study (i.e. motor, sensory experiments) 1. </li>
 <li>Drill screwholes into the bone and place the ground and stabilizing screws. Always use stainless steel or titanium screws. Small jeweler’s screws (for example #2-56, or #00-80) with as many threads per inch as possible are desirable. </li>
</ol>
3. Silicon Electrode Implant Procedures
<ol>
 <li>Drill the craniotomy after implanting screws. Drill four shallow pilot marks for the corners of the craniotomy. Using pilot marks as a guide drill out the perimeter of the craniotomy. Remove the center mass of bone that was not drilled using a pair of sturdy forceps. The edge of the open craniotomy may need to be cleaned with further drilling. Thin pieces of bone may be clipped with a pair of microrongeurs. Plan your surgery carefully to avoid major blood vessels such as the Sagittal Sinus, which may appear within 0.5 mm of the midline longitudinal suture 1. Puncturing the Sagittal sinus can cause extensive bleeding. Exposed dura should be kept hydrated with aCSF or Saline.</li>
 <li> To pierce the dura mater you will need to fashion a small hook using a sterile hypodermic needle of small gauge (e.g., &lt; 28 gauge). Take the bevel of the needle and press it flat against a firm surface (such as the flat part of a scalpel) tilting slightly to form a 90 degree bend at the point. Use this hook to catch the surface of the dura, and lift upwards from the brain surface. The dura can be cut using micro scissors or may be torn using lateral movements of the dura hook. Take care to avoid blood vessels on the surface of the brain when using the dura hook. You should notice CSF leaking out when dura is resected and a difference in color from the surface of the dura. </li>
 <li>Carefully attach the ground wire of the silicon electrode around the base of the ground screw, and tact in place with dental cement. The silicon electrodes should be placed carefully so that the electrodes cable leads are arched over the craniotomy. </li>
 <li>Implants will be placed using a linear motor actuator placed on a stereotaxic apparatus. To attach the electrode to the insertion device, Polyethylene glycol (PEG) is heated with a soldering iron and applied to insertion rod and the recording electrode. </li>
 <li>With the electrode secured, manually lower the tip of the electrode to the desired stereotaxic location on the surface of the brain. </li>
 <li>Using the software interface to the linear actuator, move the electrode into the desired depth within the brain tissue. </li>
 <li>Secure the recording electrode in the brain by attaching PEG from an adjacent screw to the electrode cable. You can now remove the electrode from the insertion device by adding saline to dissolve the PEG bound. Raise the insertion device away from the craniotomy and repeat for each electrode. </li>
 <li>Cover the exposed craniotomy with saline soaked Gelfoam. A silicone polymer is then used to cover the electrode cable and protect it from the dental acrylic. Position the connector in the final location, then apply dental acrylic to make a robust headcap. </li>
</ol>
4. MicroECoG Electrode Implant Procedures
<ol>
 <li>Implantation of the microECoG electrode will involve a slightly larger craniotomy. For a 5 x 5 mm device, a 6 x 6 mm craniotomy must be made. Before drilling the craniotomy, UV-curable dental acrylic is applied to the periphery of the craniotomy site while it is still dry and not in danger of touching the dura or pia. </li>
 <li>A sterile surgical drill is used with a #107 burr to drill off the surface of bone in the general shape of the craniotomy. The smaller #106 burr can then be used to drill out the rest of the bone down to a thin transparent layer. Rongeurs will then be able to lift off the remaining piece of bone. The microECoG can be implanted epidurally or subdurally. Again, keep the dura well hydrated with artificial CSF or Saline. </li>
 <li>In order to implant the microECoG, place a stereotaxic arm over the open skull, and secure the electrode to the arm using sterile tape. The electrode can now be lowered down into the craniotomy. Make sure the electrode sites are facing downward and will be making contact with the dura or pial surface. If kept moist, the electrode should slide onto the tissue and will stay in place. </li>
 <li>The ground wire is connected to the ground screw by wrapping around at least three times over and under itself. The ground screw can be any screw that has come into contact with the dura. The reference wire can also be tied to the reference screw in the same manner. </li>
 <li>Small pieces of saline soaked Gelfoam should be placed surrounding the electrode where there is dura or pia exposed. A small amount of saline soaked Gelfoam should also cover the top of the thin film electrode. UV-curable dental acrylic can be applied to the top of the Gelfoam and can be used to create a stable head cap. The acrylic is applied directly to the thin film cable covering it until the connector is reached. Be careful not to cover beyond the bottom of the connector cap. </li>
 <li>Alternatively, the implantation of the microECoG in 4.3 can be immediately followed by the implantation of a silicon microelectrode array (steps 3.2-3.6) through small holes that are manufactured in the microECoG substrate. This allows for simultaneous recording of both single units at various depths along with high resolution field recordings from the surrounding brain surface. </li>
</ol>
5. Postoperative Recovery
<ol>
 <li>After the cement has completely hardened, suture the skin tightly around the head-cap and remove the animal from the stereotaxic frame. </li>
 <li>Apply antiseptic powder or antibiotic ointment copiously around the wound. If there is any bleeding from the ears, place some antibiotic well into the ear canal. </li>
 <li>Keep the animal warm as barbiturates prevent the animal from maintaining its body heat. House each chronically implanted animal in a separate cage. It usually takes four to seven days for the animal to recover completely from the surgery. </li>
</ol>
6. Representative Results
 A successful silicon electrode implant surgery will have recording sites with impedances measuring between 500kOhm-2MOhm, and thin-film electrodes between 10kOhm-50kOhm (at 1kHz). The neural signal can be checked immediately post surgery as well. You should be able to see spikes on the implanted electrodes and see slow wave oscillations on the thin film surface electrode (Figure 1). 
<img src="/files/ftp_upload/3565/3565fig1.jpg" alt="Electrophysiology waveforms, diagram; shows brain activity data, includes time and voltage scales." data-altupdatedat="1787630408000" data-alt="Figure 1"> 
Figure 1. Representative results of single unit activity and ECoG oscillations. a) Wide-band data from 6 simultaneously recorded channels of a chronic silicon electrode implanted in the neocortex. Note that spikes can often be seen across recording sites. b) ECoG oscillations from 6 channels of a 16-channel thin-film uECoG electrode array on the surface of the brain. The mean of all 16 signals were removed from each trace (common average referencing), and a 500 Hz digital low pass filter was applied.

<ol><li>Paxinos, G. A. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aPaxinos%2C+GA+%22The+Rat+Brain+in+Stereotaxic+Coordinates%22">The Rat Brain in Stereotaxic Coordinates</a>. , Sixth Edition, Academic Press. (2007).</li>
<li>Fujisawa, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Behavior-dependent+short-term+assembly+dynamics+in+the+medial+prefrontal+cortex%5BTitle%5D)+AND+%22Nat.+Neurosci%22%5BJournal%5D)">Behavior-dependent short-term assembly dynamics in the medial prefrontal cortex.</a> Nat. Neurosci. 11 (7), 823-833 (2008).</li>
<li>Merrill, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Electrical+stimulation+of+excitable+tissue%3A+design+of+efficacious+and+safe+protocols%5BTitle%5D)+AND+%22J.+Neurosci.+Methods%22%5BJournal%5D)">Electrical stimulation of excitable tissue: design of efficacious and safe protocols.</a> J. Neurosci. Methods. 141, 171-171 (2005).</li>
<li>Gage, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Naive+coadaptive+cortical+control%5BTitle%5D)+AND+%22J.+Neural+Eng%22%5BJournal%5D)">Naive coadaptive cortical control.</a> J. Neural Eng. 2, 52-52 (2005).</li>
<li>Marzullo, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Development+of+Closed-Loop+Neural+Interface+Technology+in+a+Rat+Model%3A+Combining+Motor+Cortex+Operant+Conditioning+With+Visual+Cortex+Microstimulation%5BTitle%5D)+AND+%22IEEE+Trans.+Neur.+Sys.+and+Rehab.+Eng%22%5BJournal%5D)">Development of Closed-Loop Neural Interface Technology in a Rat Model: Combining Motor Cortex Operant Conditioning With Visual Cortex Microstimulation.</a> IEEE Trans. Neur. Sys. and Rehab. Eng. 18 (2), 117-126 (2010).</li>
<li>Maynard, E. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+Utah+intracortical+electrode+array%3A+a+recording+structure+for+potential+brain-computer+interfaces%5BTitle%5D)+AND+%22Electroencephalogr.+Clin.+Neurophysiol%22%5BJournal%5D)">The Utah intracortical electrode array: a recording structure for potential brain-computer interfaces.</a> Electroencephalogr. Clin. Neurophysiol. 102, 228-239 (1997).</li>
<li>Kipke, D. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Silicon-substrate+intracortical+microelectrode+arrays+for+long-term+recording+of+neuronal+spike+activity+in+cerebral+cortex%5BTitle%5D)+AND+%22IEEE+Trans.+Neural+Syst.+Rehab.+Eng%22%5BJournal%5D)">Silicon-substrate intracortical microelectrode arrays for long-term recording of neuronal spike activity in cerebral cortex.</a> IEEE Trans. Neural Syst. Rehab. Eng. 11 (2), 151-155 (2003).</li>
<li>Vetter, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Chronic+neural+recording+using+silicon-substrate+microelectrode+arrays+implanted+in+cerebral+cortex%5BTitle%5D)+AND+%22IEEE+Trans.+Biomed.+Eng%22%5BJournal%5D)">Chronic neural recording using silicon-substrate microelectrode arrays implanted in cerebral cortex.</a> IEEE Trans. Biomed. Eng. 51 (6), 896-904 (2004).</li>
</ol>

DRK is part-owner of NeuroNexus Technologies.

There is an increasing interest in using intracortical and surface multichannel recording interfaces for researching brain function 2, providing microstimulation 3, or control signals for neuroprosthetic systems 4,5. The methods outlined in this video demonstrate how to implant chronic penetrating and surface electrode systems. While other silicon chronic electrode systems exist 6, we have focused on implanting planar electrodes developed by NeuroNexus Technologies 7,8. Techniques for the implantation of other electrode systems will vary considerably.
Of the surgical steps described, mounting the animal in the stereotaxic ear bars may be the most difficult and the most important step in determining the accuracy of placement of the implanted electrodes. Extreme care must be taken, therefore, to assume that each ear-bar tip is properly positioned in the auditory meatus. After assurance that the ear-bar tip is in the auditory meatus of the animal&#x2019;s right ear, release the animal&#x2019;s neck with your right hand while your left thumb and forefinger continue to support the head and apply pressure of the head against the ear-bar tip. With your right hand, push the loosened left ear bar into the auditory canal and apply slight inward pressure. Move the left side of the animal&#x2019;s head down and forward and all around until you can feel the left ear-bar tip slip into the auditory meatus. With your right hand, continue to apply pressure on the left ear bar. Release the animal&#x2019;s head and, with your now free left hand, tighten the set screw of the left ear bar.

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surgical implantation of chronic neural electrodes for recording single unit activity and electrocorticographic signals

Surgical Implantation of Chronic Neural Electrodes for Recording Single Unit Activity and Electrocorticographic Signals

The success of long-term electrophysiological recordings often depends on the quality of the implantation surgery. Here we provide useful information for surgeons who are learning the process of implanting electrode systems. We demonstrate the implantation procedure of both a penetrating and a surface electrode. The surgical process is described from start to finish, including detailed descriptions of each step throughout the procedure. It should also be noted that this video guide is focused towards procedures conducted in rodent models and other small animal models. Modifications of the described procedures are feasible for other animal models.

We provide useful information for surgeons who are learning the process of implanting chronic neural recording electrodes. Techniques for both penetrating and surface electrode systems are described in a rodent animal model.

The success of long-term electrophysiological recordings often depends on the quality of the implantation surgery.  Here we provide useful information for ...

The overall goal of this procedure is to implant an electrode for chronic electrophysiological recordings. This is accomplished by first anesthetizing and preparing the animal for surgery. Once ready, an incision is made down the midline and the top of the skull is exposed.Next holes are drilled to hold screws and a craniotomy is performed. Finally, the electrode is implanted and a protective cap is built from dental acrylic. When finished, the electrodes are connected to a signal acquisition system, and recordings can be made of electrophysiological signals including action potentials and local field potentials.The main advantage of chronic electrophysiology recordings is it allows us to study awake, behaving animals free of anesthesia. Now, this message could help us answer key questions, and neuroscience are difficult to ascertain from acute surgeries such as learning in memory, attention, decision making, and much more. Today's surgeries are going to be performed by Sarah Nik and Colin Stetner, Having induced a surgical plane of anesthesia in the animal, which was confirmed by the absence of a pain reflex via a toe pinch, prepare the animal for surgery.Shave the animal from between the eyes to behind the ears, then apply a lubricant to the eyes. Then scrub the shaved region three times, alternating between Isop profile, alcohol and Betadine. Attach measurement devices and mount the animal in Stereotaxic ear bars.Now, carefully position each ear bar tip in the auditory ATU by first shifting the animal to position the first air bar, and second, using slight inward pressure to direct the second ear bar. Grasp the animal behind the ears and wiggle back and forth firmly. If the animal is mounted properly, the head will feel rigid and secured.Re sterilize the head using a scalpel, make an incision down the midline. Use clamps to hold back the skin using sterile swabs. Remove underlying connective tissue that adheres to the bone.The swab tip can absorb and minimize bleeding. At this point, clamps can be repositioned to tissue beneath the skin, disinfect and clean the bone's surface using hydrogen peroxide. Then dry the bone using a gauze pad, using the BMA and lambda points, a stereotaxic tower is used to identify the drilling position of the craniotomy.A pen or shallow drilling will mark the surface. Now drill screw holes into the bone for anchoring screws and ground place anchor screws around the perimeter and place the ground screw posterior of Lambda. Leave the area next to the craniotomy, free from screws.After implanting screws, drill the craniotomy begin by drilling four shallow pilot marks for the corners of the craniotomy, followed by drilling out the perimeter of the craniotomy. If possible, avoid the sagittal sinus because it can cause extensive bleeding. Now, remove the center mass bone using a pair of sturdy forceps and hydrate the exposed dura with artificial CSF or saline fashion.A small 90 degree hook from a 28 gauge or smaller hypodermic needle, avoiding blood vessels. Hook the surface of the dura and lift it off the brain. Use micro scissors to trim any connective tissue.CSF will leak out when the dura is resected. Secure the linear motor actuator on a stereotaxic apparatus. Carefully attach the ground wire of the silicon electrode around the base of the ground screw.The electrode is placed so that the cables hover over the craniotomy. Next, attach the recording electrode to the insertion device with heated PEG. Then manually lower the tip of the electrode to the desired stereotaxic location on the surface of the brain.Using the software interface to the linear actuator, move the electrode into the desired depth within the brain tissue. Secure the recording electrode cable to the brain by attaching it to an adjacent screw using quick seal. Once secured, remove the electrode from the insertion device by dissolving that PEG connection with saline.Raise the insertion device from the brain. When finished, cover the exposed craniotomy with saline soak, gel foam, or an alginate gel, and apply a silicon polymer to cover and protect each electrode cable. Apply acrylic to secure the implant site and allow it to harden.Next, position the connector to its final location and apply dental acrylic to make a robust head cap. Allow the cement to harden. Then proceed with the section titled Postoperative Recovery.For the implantation of a five by five millimeter device, prepare a six by six millimeter craniotomy between Lambda and Bgma to reduce the time the craniotomy is open and keep it clean. Apply a UV curable dental acrylic to the dry periphery of the cap and craniotomy site before drilling. Now, use a 1 0 7 bur to drill off the surface of bone in the general shape of the craniotomy down to a thin transparent layer followed by a number 1 0 6 bur.To finish thinning the edges, lift off the remaining piece of bone using wrongs. Keep the dura well hydrated with artificial CSF or saline soak gel foam. Otherwise, the electrode will not slide into the tissue.Using sterile tape, secure the micro ECOG electrode to the stereotaxic. Calm over the open skull. Lower the electrode, making sure the electrode sites are facing downward to contact the dura or peel surfaces.Now place small pieces of saline soak gel foam around the electrode where there is dura or peer exposed and on top of the thin film electrode. Then stabilize the head cap by applying UV curable dental acrylic over the gel foam and up to the connector. Take care not to cover the connector beyond the bottom of the cap.Leave the screws uncovered and accessible to wires. Once the cap is stable, cut the tape and back away the tower. Connect the ground wire to any screw touching the dura by wrapping it around that screw at least three times over and under itself.Then connect the reference wire to another screw in the same manner. Finally, the cap is finished with some additional acrylic. Once the cement has hardened, the surgical site will be ready for closure.To begin the postoperative recovery, remove the animal from the frame. Keep the animal warm and provide supplementary oxygen until the animal can independently maintain normal oxygen levels. House each chronically implanted animal in a separate cage.It usually takes four to seven days for the animal to recover completely from the surgery. A successful implant will have predictable impedances measured at one kilohertz immediately post surgery. The neural signal shows spikes on the implanted electrodes and slow wave oscillations on the thin film surface electrode.After watching this video, you should have a good understanding of how to do chronic surgeries with practice. You should be able to complete it within a couple hours.

surgical-implantation-chronic-neural-electrodes-for-recording-single

Research

JoVE Journal

Neuroscience

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Implantation of Electrodes into a Mouse Cortex for Electrocorticographic Recordings

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Implanting an On-Head Electrode System in a Rat Model for Real-Time Seizure Detection

Different electrode coatings affect neural recording performance through changes to electrochemical, chemical and mechanical properties. Comparison of electrodes in vitro is relatively simple, however comparison of in vivo response is typically complicated by variations in electrode/neuron distance and between animals. This article provides a robust method to compare neural recording electrodes.

A Method for Systematic Electrochemical and Electrophysiological Evaluation of Neural Recording Electrodes

Patients implanted with intracranial electrodes provide a unique opportunity to record neurological data from multiple areas of the brain while the patient performs behavioral tasks.  Here, we present a method of recording from implanted patients that can be reproducible at other institutions with access to this patient population.

Performing Behavioral Tasks in Subjects with Intracranial Electrodes

We designed a procedure in which a formaldehyde-fixed human cadaver is used to assist neurosurgeons in training for the implantation of microelectrode arrays into the neocortex of the human brain.

Surgical Training for the Implantation of Neocortical Microelectrode Arrays Using a Formaldehyde-fixed Human Cadaver Model

This detailed protocol describes transcranial stimulation electrode placement on the temporal bone in order to investigate the short- and long-term effects of transcranial electrical stimulation in freely moving rats.

Chronic Transcranial Electrical Stimulation and Intracortical Recording in Rats

We have developed a whole-cortical electrocorticographic array for the common marmoset that continuously covers almost the entire lateral surface of cortex, from the occipital pole to the temporal and frontal poles. This protocol describes a chronic implantation procedure of the array in the epidural space of the marmoset brain.

Chronic Implantation of Whole-cortical Electrocorticographic Array in the Common Marmoset

Described below is a method for implantation of multiple polymer electrode arrays across anatomically distant brain regions for chronic electrophysiological recording in freely moving rats. Preparation and surgical implantation are described in detail, with emphasis on design principles to guide adaptation of these methods for use in other species.

Chronic Implantation of Multiple Flexible Polymer Electrode Arrays

Here, we present a method for the long-term performance and safety assessment of soft subdural electrode arrays in a minipig model, describing surgical method and tools, postoperative magnetic resonance imaging, electrophysiology of the auditory cortex, electrochemical properties of the implant, and postmortem immunochemistry.

Subdural Soft Electrocorticography (ECoG) Array Implantation and Long-Term Cortical Recording in Minipigs

Here, we introduce a lightweight, cost-effective probe implant system for chronic electrophysiology in rodents optimized for ease of use, probe recovery, experimental versatility, and compatibility with behavior.

The DREAM Implant: A Lightweight, Modular, and Cost-Effective Implant System for Chronic Electrophysiology in Head-Fixed and Freely Behaving Mice

Learn surgical implantation of chronic neural electrodes in rodents for electrophysiological recordings. This method enables single unit and electrocorticographic signal acquisition in awake, behaving animals.

Surgical Implantation of Chronic Neural Electrodes for Recording Single Unit Activity and Electrocorticographic Signals

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