We thank Daniel Carpi for his help and early contributions to this project. We also thank Lucrecia Novoa for her assistance with artwork and images. This work was supported by NIH/NIAID program grant 5P01AI073693-03.

1. Tetrode Fabrication
<ol>
	<li>Start by using insulated 12.5 &mu;m (0.0005") diameter core platinum-iridium wire from California Fine Wire. The length of the wire should be cut to the appropriate length for the target structure. For example, cut the wire to at least 30 cm long for targeting the dorsal subiculum or hippocampus.</li>
	<li>Fold the wire over at the center so that there are two parallel wires which will be 15 cm in length. Drape the midpoint of this wire over a horizontal arm to form four parallel wires ...

<ol>
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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Large-scale+chronically+implantable+precision+motorized+microdrive+array+for+freely+behaving+animals.">Large-scale chronically implantable precision motorized microdrive array for freely behaving animals.</a> J. Neurophysiol. 100 (4), 2430-2440 (2008).</li><li>Harris, K. D., Henze, D. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+tetrode+spike+separation+as+determined+by+simultaneous+intracellular+and+extracellular+measurements.">Accuracy of tetrode spike separation as determined by simultaneous intracellular and extracellular measurements.</a> J. Neurophysiol. 84 (1), 401-414 (2000).</li><li>Henze, D. A., Borhegyi, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intracellular+features+predicted+by+extracellular+recordings+in+the+hippocampus+in+vivo.">Intracellular features predicted by extracellular recordings in the hippocampus in vivo.</a> J. Neurophysiol. 84 (1), 390-400 (2000).</li><li>Chang, E. H., Huerta, P. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurophysiological+correlates+of+object+recognition+in+the+dorsal+subiculum.">Neurophysiological correlates of object recognition in the dorsal subiculum.</a> Front. Behav. Neurosci. 6, 46 (2012).</li><li>Gray, C. M., Maldonado, P. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tetrodes+markedly+improve+the+reliability+and+yield+of+multiple+single-unit+isolation+from+multi-unit+recordings+in+cat+striate+cortex.">Tetrodes markedly improve the reliability and yield of multiple single-unit isolation from multi-unit recordings in cat striate cortex.</a> J. Neurosci. Methods. 63 (1-2), 43-54 (1995).</li><li>O'Keefe, J., Dostrovsky, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+hippocampus+as+a+spatial+map.+Preliminary+evidence+from+unit+activity+in+the+freely-moving+rat.">The hippocampus as a spatial map. Preliminary evidence from unit activity in the freely-moving rat.</a> Brain Res. 34 (1), 171-175 (1971).</li><li>Wilson, M. A., McNaughton, B. 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The authors declare that they have no competing financial interests.

We have described a set of techniques for constructing light and compact microdrives for the recording of extracellular unit and field potential activity in mice. By building custom microdrives with bases fashioned from acrylic glass (methyl methacrylate), the core system can be easily adapted for multiple drives and for the targeting of a wide array of neural regions. We have successfully modified the system for recording from multiple brain targets and with larger arrays for recordings in mice. With further modif...

The use of the microelectrode technique for recording extracellular neural signals in vivo has a long and valued tradition in neuroscience 1, 2. The ability to record electrical activity from many brain regions in freely behaving animals is, however, a more recent technology that is becoming increasingly common as the software packages for the acquisition, analysis and discrimination of neural signals becomes more sophisticated and user-friendly 3, 4. The technological advances on the software side have also been accompanied by reductions in the weight and bulk of the implantable devices, which have been scaled down sufficiently for recording in small mammals, such as mice. By using lightweight (mostly plastic) components, researchers are able to construct microdrives that allow for independent positioning of electrodes or tetrodes to target a wide variety of brain regions 5-7. Even deep brain structures, such as the amygdala 6 and the striatum 5, can be routinely targeted with the selection of an appropriately long drive screw. These recording techniques allow researchers to obtain high-fidelity neural signals and are in register with the electrical activity of single neurons recorded intracellularly 8, 9. Using these types of microdrives, we have successfully recorded single-units from mice for up to two months after implantation 10. In addition, the lightweight nature of the devices (approximately 1.5-2.0 g) has resulted in behavioral performance that is comparable to non-implanted mice in many behavioral tasks. In particular, we have demonstrated that implanted mice exhibit normal performance in the novel object recognition task 10 and the object place task (unpublished data).	
	The use of microdrives coupled to multiple tetrodes allows researchers to monitor and analyze neural activity at the network level while also recording from multiple single-units within the brain. Recording with these tetrodes has several major advantages for unit identification purposes and enables the high accuracy acquisition and discrimination of multiple single-units 11. We describe how to fabricate and gold-plate tetrode bundles and then subsequently load them into driveable electrode carriers. One type of drive carrier we describe is commercially available and the other is a simple, but easily expandable, drive design that can accommodate multiple carriers and tetrode arrangements without a significant investment of resources.

<table border="1">
		<tbody>
		 <tr>
			<td>Name of Reagent/Material</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		 </tr>
		 <tr>
			<td>0.0005" (12.5 &mu;M) diameter Platinum-Iridium wire </td>
			<td>California Fine Wire</td>
			<td>CFW#100-167</td>
			<td>HML VG insulated <a href="http://www.calfinewire.com" target="_blank">www.calfinewire.com</a></td>
		 </tr>
		 <tr>
			<td>0.002" (50 &mu;M) diameter Stableohm 675 wire</td>
			<td>California Fine Wire</td>
			<td>CFW# 100-188</td>
			<td>HML insulated Ni-Cr</td>
		 </tr>
		 <tr>
			<td>polyamide tubing</td>
			<td>Polymicro Technologies</td>
			<td>1068150020</td>
			<td>99 micron I.D., 166 micron O.D. <a href="http://www.polymicro.com" target="_blank">www.polymicro.com</a></td>
		 </tr>
		 <tr>
			<td>brass guides</td>
			<td>World Plastics Inc</td>
			<td></td>
			<td>3.3 x 6.6 mm</td>
		 </tr>
		 <tr>
			<td>Delrin blocks</td>
			<td>World Plastics Inc</td>
			<td></td>
			<td>3.13 x 2.5 mm</td>
		 </tr>
		 <tr>
			<td>Fillister head brass screws</td>
			<td>J.I. Morris Co.</td>
			<td>00-90 x 1/2</td>
			<td>drive screw <a href="http://www.jimorrisco.com" target="_blank">www.jimorrisco.com</a></td>
		 </tr>
		 <tr>
			<td>hex brass nuts</td>
			<td>J.I. Morris Co.</td>
			<td>00-90</td>
			<td></td>
		 </tr>
		 <tr>
			<td>Fillister head brass screws</td>
			<td>J.I. Morris Co.</td>
			<td>000-120 x 3/32</td>
			<td>EIB mount and ground screw</td>
		 </tr>
		 <tr>
			<td>plexiglass acrylic</td>
			<td>Canal Street Plastics</td>
			<td></td>
			<td>5 mm thick, clear, <a href="http://www.cpcnyc.com" target="_blank"> www.cpcnyc.com</a></td>
		 </tr>
		 <tr>
			<td>cyanoacrylate</td>
			<td>Krazy Glue</td>
			<td></td>
			<td>2 g tube</td>
		 </tr>
		 <tr>
			<td>electronic interface board</td>
			<td>Neuralynx</td>
			<td>EIB-18</td>
			<td><a href="http://www.neuralynx.com" target="_blank">www.neuralynx.com</a></td>
		 </tr>
		 <tr>
			<td>non-cyanide gold solution</td>
			<td>SIFCO</td>
			<td>SIFCO 5355</td>
			<td><a href="http://www.sifcoasc.com" target="_blank">www.sifcoasc.com</a></td>
		 </tr>
		 <tr>
			<td>VersaDrive 4</td>
			<td>Neuralynx</td>
			<td></td>
			<td>four tetrode model</td>
		 </tr>
		 <tr>
			<td>tetrode assembly station</td>
			<td>Neuralynx</td>
			<td></td>
			<td></td>
		 </tr>
		 <tr>
			<td>motorized tetrode spinner</td>
			<td>Neuralynx</td>
			<td>tetrode spinner 2.0</td>
			<td></td>
		 </tr>
		 <tr>
			<td>VersaDrive jig</td>
			<td>Neuralynx </td>
			<td></td>
			<td></td>
		 </tr>
		 <tr>
			<td>soldering iron</td>
			<td>Radio Shack </td>
			<td>64-2802B</td>
			<td><a href="http://www.radioshack.com" target="_blank">www.radioshack.com</a></td>
		 </tr>
		 <tr>
			<td>nanoZ</td>
			<td>Neuralynx</td>
			<td></td>
			<td></td>
		 </tr>
		 <tr>
			<td>small bit drill/driver</td>
			<td>Ram Products </td>
			<td>Rampower 35</td>
			<td>with footpedal controller, <a href="http://www.ramprodinc.com" target="_blank">www.ramprodinc.com</a></td>
		 </tr>
		 <tr>
			<td>drill bits</td>
			<td>Small Parts, Inc.</td>
			<td></td>
			<td>3/32" bits, <a href="http://www.smallpartsinc.com" target="_blank">www.smallpartsinc.com</a></td>
		 </tr>
		 <tr>
			<td>dissecting microscope</td>
			<td>Olympus </td>
			<td>SZ-60</td>
			<td><a href="http://www.olympusamerica.com" target="_blank">www.olympusamerica.com</a></td>
		 </tr>
		 <tr>
			<td>heat gun</td>
			<td>Alphawire</td>
			<td>Fit gun 3</td>
			<td>use setting "1" only, <a href="http://www.alphawire.com" target="_blank">www.alphawire.com</a></td>
		 </tr>
		 <tr>
			<td>26 AWG copper wire</td>
			<td>Arcor Electronics</td>
			<td>F26</td>
			<td>for ground wires, <a href="http://www.arcorelectronics.com" target="_blank"> www.arcorelectronics.com</a></td>
		 </tr>
		 <tr>
			<td>soldering flux</td>
			<td>Eagle</td>
			<td>2 oz, #205</td>
			<td></td>
		 </tr>
		 <tr>
			<td>0.02" diameter solder</td>
			<td>Kester</td>
			<td>24-6337-0010</td>
			<td><a href="http://www.kester.com" target="_blank"> www.kester.com</a></td>
		 </tr>
		 <tr>
			<td>benchtop vise</td>
			<td>Vacu-Vise</td>
			<td>Model 300</td>
			<td></td>
		 </tr>
		 <tr>
			<td>fiber optic light</td>
			<td>Nikon </td>
			<td>MKII</td>
			<td>dual light arms, <a href="http://www.nikon.com" target="_blank"> www.nikon.com</a></td>
		 </tr>
		 <tr>
			<td>5-min epoxy</td>
			<td>Allied Electronics</td>
			<td></td>
			<td>25 ml, <a href="http://www.alliedelec.com" target="_blank"> www.alliedelec.com</a></td>
		 </tr>
		 <tr>
			<td>fine tweezers</td>
			<td>Roboz Surgical Instrument Co.</td>
			<td>RS-4907, RS-5010</td>
			<td>INOX material, <a href="http://www.roboz.com" target="_blank"> www.roboz.com</a></td>
		 </tr>
		 <tr>
			<td>micro dissecting scissors</td>
			<td>Roboz Surgical Instrument Co.</td>
			<td>RS-5880</td>
			<td></td>
		 </tr>
		</tbody>
 </table>
 Table 1. Materials and reagents used for constructing tetrodes and microdrives.

construction of microdrive arrays for chronic neural recordings in awake behaving mice

State-of-the-art electrophysiological recordings from the brains of freely behaving animals allow researchers to simultaneously examine local field potentials (LFPs) from populations of neurons and action potentials from individual cells, as the animal engages in experimentally relevant tasks. Chronically implanted microdrives allow for brain recordings to last over periods of several weeks. Miniaturized drives and lightweight components allow for these long-term recordings to occur in small mammals, such as mice. By using tetrodes, which consist of tightly braided bundles of four electrodes in which each wire has a diameter of 12.5 &mu;m, it is possible to isolate physiologically active neurons in superficial brain regions such as the cerebral cortex, dorsal hippocampus, and subiculum, as well as deeper regions such as the striatum and the amygdala. Moreover, this technique insures stable, high-fidelity neural recordings as the animal is challenged with a variety of behavioral tasks. This manuscript describes several techniques that have been optimized to record from the mouse brain. First, we show how to fabricate tetrodes, load them into driveable tubes, and gold-plate their tips in order to reduce their impedance from M&Omega; to K&Omega; range. Second, we show how to construct a custom microdrive assembly for carrying and moving the tetrodes vertically, with the use of inexpensive materials. Third, we show the steps for assembling a commercially available microdrive (Neuralynx VersaDrive) that is designed to carry independently movable tetrodes. Finally, we present representative results of local field potentials and single-unit signals obtained in the dorsal subiculum of mice. These techniques can be easily modified to accommodate different types of electrode arrays and recording schemes in the mouse brain.

After implanting the microdrive and lowering the electrodes to the intended brain targets, an amplified data acquisition system, such as a Neuralynx Lynx-8, is needed for recording neural signals. Representative neural recordings of local field potentials (LFPs) and single-unit action potentials (often termed "spikes") from the mouse dorsal subiculum are shown in Figure 2. LFP signals were sampled at 3 kHz and band-pass filtered between 0.1-500 Hz (Figure 2A and 2B...

Watch this Scientific Journal Video about Construction of Microdrive Arrays for Chronic Neural Recordings in Awake Behaving Mice at JoVE.com

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

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.

State-of-the-art electrophysiological recordings from the brains of freely behaving animals allow researchers to simultaneously examine local field ...

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20.0K Views.  North Shore LIJ Health System. 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.