fabrication of an electromyographic set of electrodes for implantation in murine muscles

<meta charset="utf8"></head><body>Tillverkning och kirurgisk implantation av elektromyografiska elektroder i möss

In recent decades, mice have become an attractive model organism for studying the mammalian motor system. Common experimental approaches involve head-fixed mice performing motor tasks alongside the monitoring and/or perturbation of neural activity1,2,3,4,5. Motor system studies in larger species (such as cats and primates) have traditionally relied upon electromyography (EMG) to measure motor output directly during such experiments6,7,8. However, recording muscle activity in mice is challenging because their musculature is too small for commercially available EMG electrodes used in large mammal experiments9. Many researchers opt to track limb kinematics through video4,10,11 and/or behavioral performance2,4,12 to probe motor output indirectly, but these methods lack the resolution to detect the millisecond-timescale influence of neural activity and perturbation thereof on muscles. Thus, recording EMG is desirable for researchers interested in direct neural control of muscles.
EMG involves measuring the voltage between two points, typically separated by a short distance roughly parallel to the fibers of the muscle being recorded. EMG electrodes come in surface (or &#34;patch&#34;) and intramuscular (or &#34;needle&#34;) varieties. Surface electrodes are placed atop the skin or overlaid on the muscle tissue and secured with adhesive or suturing. As such, surface electrodes are less invasive than intramuscular electrodes and are most popular with humans, cats, and primates due to their relative ease of use. Surface electrodes have also been used successfully with rats and mice13,14; however, they must be hand-fabricated and surgically implanted under the skin due to the tendency of rodents to try to remove foreign objects while grooming. Intramuscular EMG electrodes, on the other hand, are surgically implanted within the muscle tissue. Because they are engulfed in muscle tissue, they provide high spatial resolution and remain fixed in position indefinitely. Thus, implanted intramuscular EMG electrodes are ideal over surface electrodes for long-term experiments using rodents. To record intramuscular EMG reliably in mice, researchers have developed a method for hand fabricating and implanting EMG electrodes in muscles as small as those in an adult mouse&#39;s forearm. These electrodes enable chronic muscle recording during motor behavior in rodents over several weeks.
The protocol described here is the result of a decade-long refinement of established methods15,16,17,18, which has yielded a procedure for hand fabricating, implanting, and recording from wire EMG electrodes chronically implanted in flexor/extensor muscle pairs of the elbow and wrist in behaving mice. The first section describes the hand fabrication of an electrode set with four electrode pairs and an 8-pin connector&#160;for the head stage interface. The next section details the surgical implantation of the electrodes intramuscularly in upper and lower arm muscles in the same surgery as headplate implantation. Finally, representative recordings from mice performing a variety of behaviors are discussed. Overall, this method is a cost-effective and customizable way to include muscle activity measurements in head-fixed behavior experiments that is ideal for labs with some electrode fabrication experience.

<meta charset="utf8"></head><body>Författare i fokus: Undersöker interaktioner mellan musmotoriska cortex och från muskelaktivitet till neural dynamik

Registrering av muskelaktivitet i frambenen hos huvudfixerade möss med kroniskt implanterade EMG-elektroder

I'm interested in how parts of mouse motor cortex, called primary and secondary motor cortex, interact with each other to influence muscle activity during different kinds of movements. So we know that both primary and secondary motor cortex project to the spinal cord, but it's unclear how they differentially influence movement. So I'm using this protocol to compare the effects of inactivating primary and secondary motor cortex on forelimb muscle activity throughout movement to understand how they differentially control movement.The use of forelimb muscle EMG has enabled us to measure the impact of optogenetic inactivation of different motor system regions on motor output. For example, we've been able to show that direct motor cortical influence on muscles is specific to certain motor behaviors and particular muscle activity states during those behaviors. New large-scale multi-electrode arrays like Neuropixels now enable us to record from large neuronal populations across multiple motor system regions simultaneously.Performing EMG recordings during these neural recordings will enable us to characterize how the interactions between these motor system regions depend on muscle activity state.

Tillverkning av en elektromyografisk uppsättning elektroder för implantation i murina muskler

fabrication-an-electromyographic-set-electrodes-for-implantation

Research

JoVE Journal

Neuroscience

Fabrication of an Electromyographic Set of Electrodes for Implantation in Murine Muscles

Recording Forelimb Muscle Activity in Head&#45;Fixed Mice with Chronically Implanted EMG Electrodes

Powerful genetic and molecular tools available in mouse systems neuroscience research have enabled researchers to interrogate motor system function with unprecedented precision in head-fixed mice performing a variety of tasks. The small size of the mouse makes the measurement of motor output difficult, as the traditional method of electromyographic (EMG) recording of muscle activity was designed for larger animals like cats and primates. Pending commercially available EMG electrodes for mice, the current gold-standard method for recording muscle activity in mice is to make electrode sets in-house. This article describes a refinement of established procedures for hand fabrication of an electrode set, implantation of electrodes in the same surgery as headplate implantation, fixation of a connector on the headplate, and post-operative recovery care. Following recovery, millisecond-resolution EMG recordings can be obtained during head-fixed behavior for several weeks without noticeable changes in signal quality. These recordings enable precise measurement of forelimb muscle activity alongside in vivo neural recording and/or perturbation to probe mechanisms of motor control in mice.

This protocol describes the hand fabrication and surgical implantation of electromyographic (EMG) electrodes in the forelimb muscles of mice to record muscle activity during head-fixed behavior experiments.

Powerful genetic and molecular tools available in mouse systems neuroscience research have enabled researchers to interrogate motor system function with ...

To begin the fabrication of the electrode set, first tie two pieces of PFA coated braided stainless steel wires together with a single knot. Insert an 18 gauge needle into a piece of corrugated cardboard. Position the knot six centimeters from the needles insertion end.Then pull the electrode strands against the cardboard to tighten it around the needle. Carefully remove the needle to maintain the knot's integrity, and pull the knot tight two times to tighten it further. Next, tape the electrode taut against a piece of flat cardboard.Ensure that the two connector end wires are together, and the insertion end wires are spread apart. With a scalpel, make precise nicks in the insulation, marking the ends where the insulation will be removed. Make a series of approximately six cuts at each marked location with two cuts each on top, at the sides, and underneath the wire.Angle the scalpel blade to cut along the loosened insulation length wise, and use a pair of forceps to carefully remove it from the wire. Strip one millimeter insulation off the end of each wire at the connector end, and five millimeters off at the insertion end. Twist the wire segments at the insertion end together, and crimp the exposed ends in the shaft of a 0.5 inch 27 gauge needle.Next, use a pair of straight forceps to carefully reinsert each soldered brass fitting back into the connector. Make sure that the wires of each electrode pair are adjacent and untangled. Coat the pin slots with epoxy to insulate all metal or wire near the connector from the tissue.

Electrode Implantation Surgery to Record Forelimb Muscle Activity in Head&#45;Fixed Mice

To begin, extend the incision on the back of the neck of an anesthetized mouse with a head plate implantation. With a blunt bone scraper, separate the skin under the neck incision from the underlying tissue. Work the scraper under the skin and behind the neck incision to clear a path for the electrodes.Insert the tip of a large needle driver through the triceps incision and out of the neck incision. Clamp the needle driver around the electrode needle lengthwise, then pull it through to the triceps incision. Next, bend a 27 gauge needle to give it a slight curve.Hold the needle with the needle driver. Then press it against the handle of a pair of forceps to result in an additional bend of five to 10 degrees. Add three total bends at different positions along the length of the needle.Next, identify the entry and exit points on the muscle. With a pair of fine forceps, remove any fat in fascia, obscuring the entry and exit site. After submerging three to five millimeters of wire parallel to the muscle fibers, use the needle driver to insert the needle into the proximal end of the muscle.Now push the needle through the muscle to the exit site. Once the needle exits the muscle, grab the tip with blunt forceps and pull the needle through. With a pair of forceps, tie a loose distal knot at the exit site.Tighten the knot down to a one centimeter loop. Push the loop with the forceps and position it over the exit site. After identifying the location over which the distal knot is to be closed, gently grasp the loop with a pair of fine bent forceps and pull the loop tight over the forceps.Remove the fine forceps from the knot. Push the knot toward the exit site with the fine bent forceps, and pull the needle end with fingers to finish tightening it. Use the straight fine forceps to grasp the exit knot, then tightly curl the distal wire around the forceps to bend the wire around the knot and toward the muscle.Finally, cut the wire off about 0.5 millimeters distal to the distal knot, leaving a small nub curled around the knot. All the implanted electrodes produced a clean electromyographic signal 36 days after implantation. However, after 72 days, the wrist extensor electrode failed.