Name: Design and Assembly of an Ultra-light Motorized Microdrive for Chronic Neural Recordings in Small Animals (Video) | JoVE Journal
Uploaded: 2012-11-08T13:00:00.000+00:00
Duration: 10 min 29 s
Description: Learn to assemble an ultra-light motorized microdrive for chronic extracellular recordings in small animals. This protocol enables stable neural activity monitoring for up to 10 weeks in freely behaving subjects.

ai_agent_IP

ai_agent

maintenance

instantTrialDurationMinutes

isBiopharma

enableNewMyJoveSectionDesign

educationFeatures

seoMetaApi

ai_copilot_institution_blacklist

ai_chat_institution_blacklist

freeAccessWindow

ssoRoleCapture

scheduledMaintenanceBanner

joveLabsFeatures

disable_autoplay_for_bots

extended_trial_duration

5 minutes

This work was supported by the Ester and Joseph Klingenstein Fund, the McKnight Endowment Fund, and NINDS 1R01NS066408-01A1.

1. Overview of Components
<ol>
	<li>A complete microdrive consists of several main components (Figure 1): a chassis that serves as the superstructure for the drive, a motor with a finely threaded output shaft, a threaded shuttle that carries the electrodes and provides a point of electrical connection, and an Omnetics (or equivalent) connector.</li>
	<li>The chassis, electrode shuttle, and electrode shuttle tubes are custom components that were designed with 3D CAD software (SolidWorks) and were machined by a local precision machinist. All other components are commercially available.</li>
	<li>Chassis and shuttle are machined from lightweight polyetherimide (PEI), while the electrode shuttle tubes are cut to size with a lathe from stainless steel hypodermic tubing (0.0293"OD x 0.00975"ID). Though these components may be cut from other materials, we have found that PEI and stainless steel have the right balance of machinability, strength, and weight for our application.</li>
	<li>To assemble the drive, a motor controller, capable of spinning the low DC-voltage stepper motor, is required. We employ a custom solution based on a three-phase motor driver IC (Faulhaber BLD05002 available from the manufacturer) in conjunction with an IC timer that provides the timestep-input. A variety of off-the-shelf solutions are also available (e.g. Faulhaber MCBL05002 or Sutter Instruments MP-285).</li>
</ol>
2. Drive Chassis Preparation and Assembly
<ol>
	<li>With fine diagonal cutters, trim the contact pins on the bottom of the Omnetics (or equivalent) connector - 1.5 mm for the rear row, 1 mm for the front row (Figure 2A). To improve the strength of the epoxy bond between the drive chassis and the connector, use a scalpel to roughen the rear surfaces of both components.</li>
	<li>Using a scalpel, cut four 15 mm long sections of polyimide tubing (0.0113" ID x 0.0133" OD) for use as wire guides. Carefully secure the chassis in a small vice with the open cavity down (Figure 2B). Use cyanoacrylate glue to attach the polyimide tubes to the chassis. They should lay flush with the rear chassis surface and be oriented parallel to each other as shown in Figure 2B.</li>
	<li>Once dry, trim the polyimide tubes to approximately 6 mm in length and remove the waste sections. The remaining tubes should be approximately 3 mm from the bottom edge of the chassis.</li>
	<li>To ensure proper clearance for mating with the headstage or cable, the connector should be mounted a few millimeters above the polyimide tubes and be parallel with the chassis surface (Figure 2B). Use epoxy (Torr Seal) to construct a small pedestal for the connector, place it on top with the shorter row of pins topmost, and add more epoxy around the connector. Do not proceed until the epoxy has completely cured.</li>
	<li>Remove the chassis from the vice, transfer to a jig that allows for connection to the motor controller (i.e., in our case, this jig is simply a rigid rod with the mating Omnetics connector affixed to one end) and orient with the front surface of the drive facing up. Guide the motor wires through the hole in the chassis and slide the motor into the groove in the base. The motor and drive shaft should be parallel to the chassis and fit snuggly against the bottom and side.</li>
	<li>Epoxy the motor to the chassis, taking care not to obstruct either the drive shaft or the space where the electrodes will be installed (see Torr Seal placement in Figure 4). Allow the epoxy to cure.</li>
	<li>Rotate the chassis so that the connector is accessible. To support the motor wires and prevent accidental breakage, add a small drop of fast-set epoxy to the wires where they emerge from the chassis. Trim, strip, and solder the wires to the appropriate contacts on the connector (Figure 2A). Test the motor to ensure smooth shaft rotation in both directions.</li>
</ol>
3. Electrode Shuttle Assembly
<ol>
	<li>To minimize the potential for motion-induced artifacts in the recordings, it is essential that the electrode shuttle fit snuggly in the chassis. Test the fit of the shuttle by threading it onto the motor shaft and running it up and down the full length of the shaft at low speed. Be careful not to wedge the shuttle in the drive and thus over-torquing the motor- it is very easy to permanently damage the plastic gearhead at this stage. If a previously spinning motor shaft ceases turning, the gearhead may be damaged.</li>
	<li>If the shuttle does not run smoothly down the shaft, inspect the chassis surfaces and the drive screw for debris. Remove with fine forceps or compressed air, coat the threading in some light mineral oil and recheck the shuttle fit.</li>
	<li>If the shuttle is too tight, use forceps and a fine grain whetstone to remove obstructing material from the side of the shuttle. Take care to remove the material evenly.</li>
	<li>If the shuttle is too loose such that it tilts and chatters during travel, glue a small sliver of transparency film to the shuttle to fill the gap between it and the chassis surface.</li>
	<li>Once the shuttle has been properly fit, remove the shuttle from the shaft and press one of the stainless steel shuttle tubes into each of the four large holes in the shuttle. Each should be centered on the shuttle with the ends of all four tubes flush (Figure 3). Secure them with a small drop of cyanoacrylate glue applied to the base of the tube. Be very careful not to allow the glue to get on the edges of the shuttle or into the tubes.</li>
	<li>Thread the completed electrode shuttle back on to the drive shaft and bring it all the way down to the base of the threading.</li>
</ol>
4. Guide Tube and Electrode Installation
<ol>
	<li>Cut four 25 mm long sections of polyimide tubing (0.0045" ID x 0.006" OD) for use as electrode guides. In addition, cut four electrodes to 40 mm sections for use as dummy electrodes which will hold the guide tubes in position during assembly. (Note that these dummy electrodes are for assembly only and will not be used for recording, so you may reuse the same ones for each assembly.) Slide each section of tube onto on to a dummy electrode such that the electrode extends ~10 mm beyond the end of the tube.</li>
	<li>Arrange each of the polyimide tubes in the chassis as shown in Figure 4A. This will result in the ends of the electrode guides, flush with each other and aligned to the base of the motor shaft, splaying out toward the electrode shuttle and the opposite ends converging at the bottom of the drive. Mix a small amount of Kwik-Cast and apply approximately 2 mm below the top end of the electrode guides. Allow to dry.</li>
	<li>Remove the dummy electrodes and reposition the free ends of the electrode guides such that they form a tight bundle at the bottom of the drive. It may be helpful to use a fine wire to hold them in place temporarily (Figure 4B). Fix the new position with more Kwik-Cast. Allow to dry.</li>
	<li>With a sharp scalpel, trim the electrode guide tubes where they extend beyond the bottom of the microdrive. When implanted, these tubes will guide the electrodes from the bottom of the drive (resting on the skull) to the surface of the brain. Thus, the length at which the tubes should be trimmed depends on the anatomy of the implantation site (Figure 5). For songbirds, this is approximately 1.5 mm.</li>
	<li>To connect an electrode to the connector, cut a 30 mm long section of insulated platinum wire (0.003" dia.) and strip 1 mm of insulation from one end. Solder it to one of the signal pins on the connector. Bend the wire under the connector and push it through one of the wire guide tubes. Pull the wire taunt and wrap it around the guide slot in the top of the chassis.</li>
	<li>With scissors or fine wire cutters, cut an electrode to ~25 mm in length. Take care to do this without bending the electrode or damaging the tip; if either occur, the electrode cannot be used. With the electrode shuttle now at the top of the shaft, insert the electrode into a polyimide tube and pull it up through the stainless steel tube in the shuttle. Position it such that the tip of the electrode is flush with the bottom end of the polyimide tube. Trim the electrode 1 mm above the shuttle tube.</li>
	<li>With a fine set of forceps, strip the insulation off the last 2 mm of the electrode and the last 2 mm of the platinum wire. Reposition the electrode in the shuttle tube, insert the platinum wire into the tube, and pin the two together by sliding a short 1 mm section of tungsten wire (0.008" dia) into the tube. This should be a tight fit that will provide both a mechanical and an electrical connection between the electrode and the wire (Figure 3).</li>
	<li>Run the shuttle up and down the length of the drive shaft to ensure continued movement.</li>
	<li>Repeat 4.5-4.8 until all electrodes have been installed.</li>
	<li>Cut a 30 mm long section of silver wire (0.005" dia) for use as a ground wire. Strip 1 mm of insulation off one end and solder to the ground pin.</li>
</ol>
5. Final Assembly and Pre-Implantation Preparation
<ol>
	<li>To reduce the friction of the electrodes against the guide tubes, fill the guide tubes with light mineral oil. Capillary action is sufficient to fill the tubes from a drop of oil placed at one end.</li>
	<li>To create a protective cover for the motor and electrodes, cut a 12 mm x 25 mm rectangle of transparency and fold it into a wide U-shape. Use cyanoacrylate to glue the cover to the outer surfaces of the chassis (Figure 6). Cut a 15 mm x 6 mm rectangle of transparency and use cyanoacrylate to glue it around the connector. To prevent interference with the connector, the long edge of the transparency should be flush with the top edge of the connector.</li>
	<li>Prior to implantation, sterilize the electrodes and guide tubes by lowering the extended electrodes into a 10:1 DI water-bleach solution for 10 min. Then, flush thoroughly with sterile water.</li>
	<li>A jig similar to that used in step 2.5 can be used to hold the microdrive in a stereotaxic manipulator during implantation.</li>
</ol>
6. Representative Results
This protocol requires approximately 5 hr of hands-on assembly time with an additional 6-8 hr interspersed for the epoxy and glue to dry. However, once the microdrive has been assembled the first time, it can be prepared for reuse (i.e., the electrodes, electrode guide tubes, and electrode wires can be replaced) in less than 2 hr. The quality and character of the recordings obtained by following this protocol will, of course, be in part dependent on the recording target, the choice of electrodes, and any processing performed at the headstage or further upstream of the microdrive. This aside, it is possible to obtain stable recordings from a behaving animal over a time-span of more than ten weeks. Examples of single unit recordings from the robust nucleus of the archistriatum (RA) in a behaving songbird is shown in Figure 7A; multi-unit activity from the same region is shown in Figure 7B.
<img alt="Electrode shuttle diagram; chassis and components for precision motion control in micro-scale systems." src="/files/ftp_upload/4314/4314fig1.jpg" data-altupdatedat="1787630408000" data-alt="Figure 1"> 
Figure 1. 3D model of the assembled motorized microdrive. The microdrive consists of several major components: (i) the chassis, (ii) motor with threaded output shaft, (iii) electrode shuttle, (iv) shuttle tubes, (v) electrodes, (vi) electrode guide tubes, and (vii) connector.
<img alt="Microfabrication diagram with labeled pads, and image of wire guide tubes with connector." src="/files/ftp_upload/4314/4314fig2.jpg" data-altupdatedat="1787630408000" data-alt="Figure 2"> 
Figure 2. A) Model and connection diagram for the connector. Motor wires: b, i, l. Electrode wires: c,d,e,f. Ground wire: k. All other pins available for auxiliary instrumentation. B) Photo of the connector attached to the chassis with Torr Seal epoxy. Note the position of both the connector and the underlying wire guide tubes. The cyanoacrylate glue holding the guide tubes in position dries clear and, thus, is not visible in the image.
<img alt="Electrode shuttle diagram with tungsten wire pin, platinum wire, motor shaft for electrochemical study." src="/files/ftp_upload/4314/4314fig3.jpg" data-altupdatedat="1787630408000" data-alt="Figure 3"> 
Figure 3. Electrode shuttle assembly.
<img alt="Electrode assembly with polyimide tubes in neuroscience experiment setup; labeled detail diagram." src="/files/ftp_upload/4314/4314fig4.jpg" data-altupdatedat="1787630408000" data-alt="Figure 4"> 
Figure 4. A) The electrode guide tubes positioned in the chassis prior to applying Kwik-Cast. B) To ensure that the electrodes exit the bottom of the drive in parallel, bring the bottom end of the guide tubes into a tight bundle before adding the last drop of the Kwik-Cast.
<img alt="Microdrive implantation diagram with craniotomy, guide tubes, skull, and electrodes for brain study." src="/files/ftp_upload/4314/4314fig5.jpg" data-altupdatedat="1787630408000" data-alt="Figure 5"> 
Figure 5. The amount that the electrode guide tubes extend beyond the bottom of the drive is specified by the anatomy of the implantation site. The diagram illustrates the dimensions that are relevant for determining the length of the guide tubes. For implanting in the songbird, 1.5 mm is sufficient.
<img alt="Microelectronics diagram with ground wire, jig, protective covers; focus on circuit components." src="/files/ftp_upload/4314/4314fig6.jpg" data-altupdatedat="1787630408000" data-alt="Figure 6"> 
Figure 6. The finished motorized microdrive with protective covers attached.
<img alt="Voltage vs time graph; electrophysiology signal analysis; neural activity comparison." src="/files/ftp_upload/4314/4314fig7.jpg" data-altupdatedat="1787630408000" data-alt="Figure 7"> 
Figure 7. Representative recordings from the robust nucleus of the archistriatum (RA) in the behaving zebra finch. A) Single-unit activity recorded with 10MΩ platinum-iridium electrodes. Top: example recording made one week after implantation. Bottom: example recording from the same electrode as above, nine weeks later. B) Multi-unit activity recorded with 1MΩ platinum electrodes. <a href="https://www.jove.com/files/ftp_upload/4314/4314fig7large.jpg" target="_blank"> Click here to view larger figure</a>.
Additional Files: The chassis, shuttle, and electrode tubes were designed with SolidWorks 2010 CAD software. These part files are provided in both the proprietary (*.sldprt) and vendor-neutral (*.iges) formats and dimensioned production drawings are provided in PDF format.

<ol><li>O'Keefe, J., Dostrovsky, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+hippocampus+as+a+spatial+map%5BTitle%5D)+AND+%22Brain+Research%22%5BJournal%5D)">The hippocampus as a spatial map.</a> Brain Research. 34, 171-175 (1971).</li>
<li>Pennartz, C. M., Berke, J. D., Graybiel, A. M., Ito, R., Lansink, C. S., van der Meer, M., Redish, A. D., Smith, K. S., Voorn, P. Corticostriatal Interactions during Learning, Memory Processing, and Decision. 29, 12831-12838 (2009).</li>
<li>Kepecs, A., Uchida, N., Zariwala, H., Mainen, Z. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Neural+correlates%2C+computation%2C+and+behavioural+impact+of+decision+confidence%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Neural correlates, computation, and behavioural impact of decision confidence.</a> Nature. 455, 227-2231 (2008).</li>
<li>Hahnloser, R. H. R., Kozhevnikov, A. A., Fee, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((An+ultra-sparse+code+underlies+the+generation+of+neural+sequences+in+a+songbird%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">An ultra-sparse code underlies the generation of neural sequences in a songbird.</a> Nature. 419, 65-70 (2002).</li>
<li>Leonardo, A., Fee, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Ensemble+Coding+of+Vocal+Control+in+Birdsong%5BTitle%5D)+AND+%22J.+Neurosci%22%5BJournal%5D)">Ensemble Coding of Vocal Control in Birdsong.</a> J. Neurosci. 25 (3), 652-661 (2005).</li>
<li>Yamamoto, J., Wilson, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Large-scale+chronically+implantable+precision+motorized+microdrive+array+for+freely+behaving+animals%5BTitle%5D)+AND+%22J.+Neurophysiol%22%5BJournal%5D)">Large-scale chronically implantable precision motorized microdrive array for freely behaving animals.</a> J. Neurophysiol. 100 (4), 2430-2440 (2008).</li>
<li>Fee, M. S., Leonardo, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Miniature+motorized+microdrive+and+commutator+system+for+chronic+neural+recording+in+small+animals%5BTitle%5D)+AND+%22J.+Neurosci.+Methods%22%5BJournal%5D)">Miniature motorized microdrive and commutator system for chronic neural recording in small animals.</a> J. Neurosci. Methods. 112, 83-94 (2001).</li>
<li>Ölveczky, B. P., Otchy, T. M., Goldberg, J. H., Aronov, D., Fee, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Changes+in+the+neural+control+of+a+complex+motor+sequence+during+learning%5BTitle%5D)+AND+%22J.+Neurophys%22%5BJournal%5D)">Changes in the neural control of a complex motor sequence during learning.</a> J. Neurophys. 106, 386-397 (2011).</li>
<li>Otchy, T. M., Ölveczky, B. P. Effects of Sensory Experience on the Development and Maintenance of a Motor Program Underlying a Complex Motor Sequence. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aOtchy%2C+TM+%22Soc.+for+Neurosci.+Abstr%22">Soc. for Neurosci. Abstr</a>. , (2011).</li>
<li>Goldberg, J. H., Adler, A., Bergman, H., Fee, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Singing-related+neural+activity+distinguishes+two+putative+pallidal+cell+types+in+the+songbird+basal+ganglia%3A+comparison+to+the+primate+internal+and+external+pallidal+segments%5BTitle%5D)+AND+%22J.+Neurosci%22%5BJournal%5D)">Singing-related neural activity distinguishes two putative pallidal cell types in the songbird basal ganglia: comparison to the primate internal and external pallidal segments.</a> J. Neurosci. 30 (20), 7088-7098 (2010).</li>
<li>Goldberg, J. H., Fee, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Singing-related+neural+activity+distinguishes+four+classes+of+putative+striatal+neurons+in+the+songbird+basal+ganglia%5BTitle%5D)+AND+%22J.+Neurophys%22%5BJournal%5D)">Singing-related neural activity distinguishes four classes of putative striatal neurons in the songbird basal ganglia.</a> J. Neurophys. 103 (4), 2002-2014 (2010).</li>
<li>Venkatachalam, S., Fee, M. S., Kleinfeld, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Miniature+headstage+with+6-channel+drive+and+vacuum-assisted+microwire+implantation+for+chronic+recording+from+neocortex%5BTitle%5D)+AND+%22J.+Neurosci.+Methods%22%5BJournal%5D)">Miniature headstage with 6-channel drive and vacuum-assisted microwire implantation for chronic recording from neocortex.</a> J. Neurosci. Methods. 90, 37-46 (1999).</li>
<li>Shirvalkar, P. R., Shapiro, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Design+and+Construction+of+a+Cost+Effective+Headstage+for+Simultaneous+Neural+Stimulation+and+Recording+in+the+Water+Maze%5BTitle%5D)+AND+%22J.+Vis.+Exp%22%5BJournal%5D)">Design and Construction of a Cost Effective Headstage for Simultaneous Neural Stimulation and Recording in the Water Maze.</a> J. Vis. Exp. (44), e2155(2010).</li>
</ol>

No conflicts of interest declared.

The protocol presented here will result in a device capable of high-quality recordings with minimal motion artifacts only if proper care is taken with construction. The fit of the shuttle in the chassis if of critical importance: too tight and the risk of overloading the motor is high; too loose and the risk of significant motion artifact is high. An ideal fit will allow the shuttle to travel the entire length of the threaded shaft without tilting out of position or chattering.
	Select...

<table><tbody><tr><td>Chassis</td><td>Custom</td><td></td><td>Cut from PEI</td></tr><tr><td>Electrode Shuttle</td><td>Custom</td><td></td><td>Cut from PEI</td></tr><tr><td>Shuttle Tubes</td><td>Custom</td><td></td><td>Cut from Stainless Steel</td></tr><tr><td>Connector</td><td>Omnetics</td><td>A7886-001</td><td>Mates to A7877-001</td></tr><tr><td>Motor w/ Gearhead</td><td>Faulhaber</td><td>0206-A-001-B-021-47:1</td><td></td></tr><tr><td>Wire Guide</td><td>Small Parts, Inc.</td><td>SWPT-0113-12</td><td></td></tr><tr><td>Electrode Guide</td><td>Small Parts, Inc.</td><td>SWPT-0045-12</td><td></td></tr><tr><td>10M&amp;#937; Pt-Ir electrodes</td><td>Microprobes, Inc</td><td>PI2PT310.0H3</td><td></td></tr><tr><td>Platinum Wire</td><td>A-M Systems</td><td>772000</td><td>For electrode wires</td></tr><tr><td>Silver Wire</td><td>A-M Systems</td><td>786000</td><td>For ground wire</td></tr><tr><td>Tungsten Wire</td><td>A-M Systems</td><td>797000</td><td>For electrode pins</td></tr><tr><td>Transparency</td><td>3M</td><td>AF4300</td><td></td></tr><tr><td>Torr Seal</td><td>Varian Inc., Agilent</td><td>9530001</td><td></td></tr><tr><td>Kwik-Cast</td><td>World Precision Instruments, Inc.</td><td>KWIK-CAST</td><td></td></tr><tr><td>Cyanoacrylate</td><td>Krazy Glue</td><td>KG517</td><td></td></tr><tr><td>Fast-Set Epoxy</td><td>Hardman</td><td>04001</td><td></td></tr><tr><td>Light Mineral Oil</td><td>Sigma-Aldrich</td><td>M5310</td><td></td></tr><tr><td>Chlorine bleach</td><td></td><td></td><td></td></tr><tr><td>Diagonal cutters</td><td></td><td></td><td></td></tr><tr><td>Scalpel blade</td><td></td><td></td><td></td></tr><tr><td>Forceps</td><td></td><td></td><td></td></tr><tr><td>Drive jig</td><td>Custom</td><td></td><td>Epoxy the mating connector to a syringe or stick</td></tr><tr><td>Small Vice</td><td></td><td></td><td></td></tr></tbody></table>

design and assembly of an ultra-light motorized microdrive for chronic neural recordings in small animals

Design and Assembly of an Ultra-light Motorized Microdrive for Chronic Neural Recordings in Small Animals

The ability to chronically record from populations of neurons in freely behaving animals has proven an invaluable tool for dissecting the function of neural circuits underlying a variety of natural behaviors, including navigation1 , decision making 2,3, and the generation of complex motor sequences4,5,6. Advances in precision machining has allowed for the fabrication of light-weight devices suitable for chronic recordings in small animals, such as mice and songbirds. The ability to adjust the electrode position with small remotely controlled motors has further increased the recording yield in various behavioral contexts by reducing animal handling.6,7
 Here we describe a protocol to build an ultra-light motorized microdrive for long-term chronic recordings in small animals. Our design evolved from an earlier published version7, and has been adapted for ease-of use and cost-effectiveness to be more practical and accessible to a wide array of researchers. This proven design 8,9,10,11 allows for fine, remote positioning of electrodes over a range of ~ 5 mm and weighs less than 750 mg when fully assembled. We present the complete protocol for how to build and assemble these drives, including 3D CAD drawings for all custom microdrive components.

The design, fabrication and assembly of an ultra-light motorized microdrive is described. The device provides a cost-effective and easy-to-use solution for chronic recordings of single units in small behaving animals.

The ability to chronically record from populations of neurons in freely behaving animals has proven an invaluable tool for dissecting the function of ...

The overall aim of this procedure is to assemble an ultra light motorized micro drive suitable for making stable extracellular recordings from behaving small animals. This is accomplished by first securely mounting the connector and motor to the chassis. The second step is to shape the shuttle to fit the chassis and attach the shuttle tubes.Next, the electrode guide tubes are installed and the recording electrodes are loaded into the micro drive. Finally, transparent covers are added to protect the electrodes and wiring from accidental damage. Once properly assembled and implanted the micro drive described may be used to record extracellular activity over a period of up to 10 weeks.Our design and assembly procedure have evolved over time to maximize ease of use and minimize cost, such that it is more practical for and accessible to a wider array of researchers than many previously published versions. A complete micro drive is shown here. It consists of several main components, a chassis that serves as the super structure for the drive a motor with a finely threaded output shaft, a threaded shuttle that carries the electrodes and provides a point of electrical connection and a noetics connector shown also at the shuffle tubes, electrodes, and electrode guide tubes.The chassis electrode shuttle and electrode shuttle tubes are custom components that were designed with a 3D CAD software and were machined by a local precision machinist. All other components are commercially available. First use diagonal cutters to trim the contact pins on the bottom of the connector.Trim the rear row of pins to 1.5 millimeters and the front row to one millimeter as shown on this schematic. Then carefully secure the chassis in a small vice with the open cavity down and use cyanoacrylate glue to attach four 15 millimeter lengths of polyamide tubing to the chassis so that they're flushed with the rear chassis surface and oriented parallel to each other as shown here. Once the cyanoacrylate glue is dry, trim the polyamide tubes to approximately six millimeters in length and remove the waist sections.The remaining tube sections should be approximately three millimeters from the bottom edge of the chassis. Next, use epoxy on the chassis to construct a small pedestal for the connector. Place the connector on top and add additional epoxy around the connector.The connector surface should be a few millimeters above the polyamide tubes and be parallel with the chassis surface. Once the epoxy has completely cured, remove the chassis from the vice and transfer to a jig with the front surface facing up. Then guide the motor wires through the hole in the chassis and slide the motor into the groove in the base.After checking that the motor and drive shaft are parallel to the chassis and fits snugly against the bottom and side, epoxy the motor to the chassis. Once the epoxy has cured, rotate the chassis so that the connector is accessible To reduce mechanical stress on the motor and wires, add a small amount of fast set epoxy to the wires where they emerge from the chassis. Now trim strip and sold the wires to the appropriate contacts on the connector.Test the motor to ensure smooth shaft rotation in both directions and then proceed to assembling the electrode shuttle. First, test the fit of the shuttle by carefully threading it onto the motor shaft and running it up and down the full length of the drive shaft. At low speed.The shuttle should fit snugly in the chassis and should not become wedged in the drive, nor should the motor shaft cease turning. If the shuttle does not move smoothly down the shaft. Inspect the surface of the chassis and the drive screw for debris.Remove any debris with fine forceps or compressed air, and then coat the threading in light mineral oil and recheck the fit. If the shuttle is too tight, use forceps and a fine grain wetstone to remove obstructing material from the side of the shuttle. Take care to remove the material evenly.Finally, if the shuttle is loose as evidenced by tilting and chattering during travel glue, a small sliver of transparency film to the shuttle to fill the gap between it and the chassis surface. Once a proper fit has been achieved, remove the shuttle from the shaft and press a stainless steel tube into each of the four large holes in the shuttle, ensuring that the tubes are centered on the shuttle and that the ends of all four tubes are flush as seen here at a small drop of cyanoacrylate glue to the base of each tube, ensuring that the glue does not get on the edges of the shuttle or into the tubes. Once the glue is dry, thread the completed electrode shuttle back onto the drive shaft and bring it all the way to the base of the threading.Cut 4 25 millimeter long sections of polyamide tubing for uses electrode guides. In addition, cut four electrodes into 40 millimeter sections for uses dummy electrodes during assembly. Slide each section of tube onto a dummy electrode such that the electrode extends around 10 millimeters beyond the end of the tube.Now arrange each of the polyamide tubes in the chassis as shown here. Mix a small amount of quick cast and apply approximately two millimeters below the top end of the electrode and allow to dry. Next, remove the dummy electrodes and reposition the free ends of the electrode guides so that they form a tight bundle at the bottom of the drive.Wrap a fine wire around the electrodes to hold them in place if need be. Then fix the new position with quick cast as shown here. Use a sharp scalp or to trim the electrode tube guides where they extend beyond the bottom of the micro drive.These tubes will eventually guide the electrodes to the surface of the brain, so the chosen length depends on the anatomy of the implantation site. Then cut a 30 millimeter long section of insulated platinum wire and strip one millimeter of insulation from one end. Next, solder it to one of the signal pins on the connector.Then bend the wire under the connector and push it through one of the wire guide tubes. Pull the wire taut and bring it to the guide slot in the top of the chassis with the electrode shuttle at the top of the shaft. Insert a 25 millimeter electrode into the polyamide tube and pull it up through the stainless steel tube.In the shuttle. Position the tip of the electrode so that it is flush with the bottom end of the polyamide tube. Then trim the electrode one millimeter above the shuttle tube.Use fine forceps to strip the insulation from the last two millimeters of the electrode and the last two millimeters of the platinum wire. Reposition the electrode such that the tip is aligned with the bottom of the guide tubes. Then insert the platinum wire into the shuttle tube and pin the two together by sliding a short one millimeter section of tungsten wire into the shuttle tube.Check that there is a tight fit between the electrode and wire to provide both a mechanical and electrical connection. Then run the shuttle up and down the length of the drive shaft to check for continued smooth movement. After installing all of the electrodes in the same manner, cut a 30 millimeter long section of silver wire for uses a ground wire.Strip one millimeter of insulation from one end and sold it to the ground pin to reduce friction of the electrodes against the guide tube walls. Place a drop of light mineral oil at the end of the guide tubes and allow capillary action to draw the oil into the tubes. Next, cut a 12 millimeter by 25 millimeter rectangle of transparency film and fold it into a wide U shape.Use glue to attach this cover to the outer surfaces of the chassis. Then cut a 15 millimeter by six millimeter rectangle of transparency. Film and use cyanoacrylate glue to secure it around the connector, ensuring that the long edge of the piece of transparency film is flush with the top edge of the connector.The final device should look like this. The following images show representative recordings from the robust nucleus of the arch AUM in the behaving zebra finch. The first image shows single unit activity recorded with a 10 mega platinum iridium electrode one week after implantation.This next image shows a recording from the same electrode used for the previous image, but captured approximately nine weeks later. Note the continued high quality of the recording by using lower impedance electrodes. Stable multiunit activity can be recorded.This final image shows multiunit activity recorded with a one mega oh platinum electrode. Once the assembly procedure is mastered, a micro drive can be fully assembled in about five hours, excluding epoxy drying time once initially built. However, the drive can be prepared for reuse in less than two hours.

design-assembly-an-ultra-light-motorized-microdrive-for-chronic

Research

JoVE Journal

Neuroscience

In this protocol we demonstrate how to fabricate a micro-drive array for chronic electrophysiological recordings in rats.

Micro-drive Array for Chronic in vivo Recording: Drive Fabrication

In this protocol we demonstrate how to fabricate and condition tetrodes for use with a micro-drive array, which was designed for chronic electrophysiological recordings in rats.  In addition, we illustrate the final stages of micro-drive array construction, which includes installing ground wires and a protective cone.

Micro-drive Array for Chronic in vivo Recording: Tetrode Assembly

The design and assembly of microdrives for in vivo electrophysiological recordings of brain signals from the mouse is described. By attaching microelectrode bundles to sturdy driveable carriers, these techniques allow for long-term and stable neural recordings. The lightweight design allows for unrestricted behavioral performance by the animal following drive implantation.

Construction of Microdrive Arrays for Chronic Neural Recordings in Awake Behaving Mice

Understanding the neural substrates of behavior requires brain circuit ensemble recording. Because of its genetic tractability, the mouse offers a model for circuit dissection and disease mimicry. Here, a method of designing and fabricating miniaturized probes is described that is suitable for targeting deep brain structure in the mouse.

Design and Fabrication of Ultralight Weight, Adjustable Multi-electrode Probes for Electrophysiological Recordings in Mice

We present the construction of a 3D-printable hyperdrive with eighteen independently adjustable tetrodes. The hyperdrive is designed to record brain activity in freely behaving rats over a period of several weeks.

Construction of an Improved Multi-Tetrode Hyperdrive for Large-Scale Neural Recording in Behaving Rats

This protocol describes the construction of a hybrid microdrive array that allows implantation of nine independently adjustable tetrodes and one adjustable opto-silicon probe in two brain regions in freely moving mice. Also demonstrated is a method for safely recovering and reusing the opto-silicon probe for multiple purposes.

Hybrid Microdrive System with Recoverable Opto-Silicon Probe and Tetrode for Dual-Site High Density Recording in Freely Moving Mice

Here, we describe a micro-drive design, surgical implantation procedure, and post-surgery recovery strategy that allow for chronic field and single-unit recordings from multiple brain regions simultaneously in juvenile and adolescent mice across a critical developmental window from postnatal day 20 (p20) to postnatal day 60 (p60) and beyond.

A Lightweight Drive Implant for Chronic Tetrode Recordings in Juvenile Mice

The protocol describes the methodology of extracellular recording in the motor cortex (MC) to reveal extracellular electrophysiological properties in freely moving conscious mice, as well as the data analysis of local field potentials (LFPs) and spikes, which is useful for evaluating the network neural activity underlying behaviors of interest.

Multichannel Extracellular Recording in Freely Moving Mice

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

A technique is described for implanting four  in vivo electrodes to monitor the neuromuscular control of feeding behavior in Aplysia californica.

Electrode Fabrication and Implantation in Aplysia californica for Multi-channel Neural and Muscular Recordings in Intact, Freely Behaving Animals

Learn to assemble an ultra-light motorized microdrive for chronic extracellular recordings in small animals. This protocol enables stable neural activity monitoring for up to 10 weeks in freely behaving subjects.

Design and Assembly of an Ultra-light Motorized Microdrive for Chronic Neural Recordings in Small Animals

Explore More Videos