We thank the Moser Lab at the Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University of Science and Technology, for the chronic neural recording procedures in rats. This work was supported by NIH grant R21 NS098146, and Human Frontier Science Program Long-Term Fellowship LT000211/2016-L to L. Lu.

1. Stereolithography of 3D Models
<ol>
	<li>Use stereolithographic techniques to print the hyperdrive parts and accessories. Each hyperdrive is comprised of eighteen shuttles, eighteen shuttle bolts, and one each of all other plastic pieces (Figure 1). 
	NOTE: The accessories are not part of the hyperdrive but are necessary for hyperdrive construction.</li>
</ol>
2. Preparation of Accessories (Figure 2).
<ol>
	<li>Prepara...

<ol>
	<li>O'Keefe, J., Recce, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phase+relationship+between+hippocampal+place+units+and+the+EEG+theta+rhythm.">Phase relationship between hippocampal place units and the EEG theta rhythm.</a> Hippocampus. 3 (3), 317-330 (1993).</li><li>Wilson, M. A., McNaughton, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamics+of+the+hippocampal+ensemble+code+for+space.">Dynamics of the hippocampal ensemble code for space.</a> Science. 261 (5124), 1055-1058 (1993).</li><li>Gothard, K. M., Skaggs, W. E., Moore, K. M., McNaughton, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Binding+of+hippocampal+CA1+neural+activity+to+multiple+reference+frames+in+a+landmark-based+navigation+task.">Binding of hippocampal CA1 neural activity to multiple reference frames in a landmark-based navigation task.</a> J Neurosci. 16 (2), 823-835 (1996).</li><li>Gray, C. M., Maldonado, P. E., Wilson, M., McNaughton, B. <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>Buzsaki, G. <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+recording+of+neuronal+ensembles.">Large-scale recording of neuronal ensembles.</a> Nat Neurosci. 7 (5), 446-451 (2004).</li><li>Fyhn, M., Hafting, T., Witter, M. P., Moser, E. I., Moser, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Grid+cells+in+mice.">Grid cells in mice.</a> Hippocampus. 18 (12), 1230-1238 (2008).</li><li>Skaggs, W. 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=EEG+sharp+waves+and+sparse+ensemble+unit+activity+in+the+macaque+hippocampus.">EEG sharp waves and sparse ensemble unit activity in the macaque hippocampus.</a> J Neurophysiol. 98 (2), 898-910 (2007).</li><li>Guo, P., Pollack, A. J., Varga, A. G., Martin, J. P., Ritzmann, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extracellular+wire+tetrode+recording+in+brain+of+freely+walking+insects.">Extracellular wire tetrode recording in brain of freely walking insects.</a> J Vis Exp. (86), (2014).</li><li>Knierim, J. J., McNaughton, B. L., Poe, G. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+spatial+selectivity+of+hippocampal+neurons+during+space+flight.">Three-dimensional spatial selectivity of hippocampal neurons during space flight.</a> Nat Neurosci. 3 (3), 209-210 (2000).</li><li>Leutgeb, S., 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=Independent+codes+for+spatial+and+episodic+memory+in+hippocampal+neuronal+ensembles.">Independent codes for spatial and episodic memory in hippocampal neuronal ensembles.</a> Science. 309 (5734), 619-623 (2005).</li><li>Lansink, C. S., 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=A+split+microdrive+for+simultaneous+multi-electrode+recordings+from+two+brain+areas+in+awake+small+animals.">A split microdrive for simultaneous multi-electrode recordings from two brain areas in awake small animals.</a> J Neurosci Methods. 162 (1-2), 129-138 (2007).</li><li>Kloosterman, F., 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=Micro-drive+array+for+chronic+in+vivo+recording:+drive+fabrication.">Micro-drive array for chronic in vivo recording: drive fabrication.</a> J Vis Exp. (26), (2009).</li><li>. Google Patents Available from: <a target="_blank" href="https://www.google.com/patents/US5928143">https://www.google.com/patents/US5928143</a> (1999)</li><li>Redish, A. D., 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=Independence+of+firing+correlates+of+anatomically+proximate+hippocampal+pyramidal+cells.">Independence of firing correlates of anatomically proximate hippocampal pyramidal cells.</a> J Neurosci. 21 (5), RC134 (2001).</li><li>Schmitzer-Torbert, N., Redish, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+activity+in+the+rodent+dorsal+striatum+in+sequential+navigation:+separation+of+spatial+and+reward+responses+on+the+multiple+T+task.">Neuronal activity in the rodent dorsal striatum in sequential navigation: separation of spatial and reward responses on the multiple T task.</a> J Neurophysiol. 91 (5), 2259-2272 (2004).</li><li>Nguyen, D. P., 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=Micro-drive+array+for+chronic+in+vivo+recording:+tetrode+assembly.">Micro-drive array for chronic in vivo recording: tetrode assembly.</a> J Vis Exp. (26), (2009).</li><li>Chang, E. H., Frattini, S. A., Robbiati, S., 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=Construction+of+microdrive+arrays+for+chronic+neural+recordings+in+awake+behaving+mice.">Construction of microdrive arrays for chronic neural recordings in awake behaving mice.</a> J Vis Exp. (77), e50470 (2013).</li><li>Vandecasteele, M., 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=Large-scale+recording+of+neurons+by+movable+silicon+probes+in+behaving+rodents.">Large-scale recording of neurons by movable silicon probes in behaving rodents.</a> J Vis Exp. (61), e3568 (2012).</li><li>Siegle, J. H., 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=Chronically+implanted+hyperdrive+for+cortical+recording+and+optogenetic+control+in+behaving+mice.">Chronically implanted hyperdrive for cortical recording and optogenetic control in behaving mice.</a> Conf Proc IEEE Eng Med Biol Soc. 2011, 7529-7532 (2011).</li><li>Brunetti, P. M., 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=Design+and+fabrication+of+ultralight+weight,+adjustable+multi-electrode+probes+for+electrophysiological+recordings+in+mice.">Design and fabrication of ultralight weight, adjustable multi-electrode probes for electrophysiological recordings in mice.</a> J Vis Exp. (91), e51675 (2014).</li><li>. Google Patents Available from: <a target="_blank" href="https://www.google.com/patents/US4575330">https://www.google.com/patents/US4575330</a> (1986)</li><li>Ludvig, N., Potter, P. E., Fox, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+single-cell+recording+and+microdialysis+within+the+same+brain+site+in+freely+behaving+rats:+a+novel+neurobiological+method.">Simultaneous single-cell recording and microdialysis within the same brain site in freely behaving rats: a novel neurobiological method.</a> J Neurosci Methods. 55 (1), 31-40 (1994).</li></ol>

Here, we describe the process of constructing a newly developed hyperdrive comprised of eighteen independently movable tetrodes. The drive can be constructed from affordable parts purchased at many available hardware stores, combined with components created by stereolithographic printing. The hyperdrive can be chronically implanted onto a rat&#39;s skull using standard surgical procedures and is capable of recording extracellular neural activity while the animal performs various behavioral tasks.
<p class="jove_conte...

In the field of systems neuroscience, scientists study the neural correlates underlying cognitive processes such as spatial navigation, memory, and decision-making. For these types of studies, it is critical to monitor the activity of many individual neurons during animal behavior. Over the past decades, two important advances have been made to meet the experimental needs for extracellular neural recording in small animals1,2,3. First was the development of the tetrode, a bundle of four microwires used to record neural activity of neurons simultaneously1,2,4. The differential signal amplitudes of activity across the four channels of a tetrode allows for the isolation of individual neuron activity from many simultaneously recorded cells5. In addition, the flexible nature of the microwires allows greater stability of the tetrode minimizing the relative displacement between the tetrode and the target cell population. Tetrodes are now widely used instead of a single electrode for many brain studies in various species, including rodents1,2,6, primates7, and insects8. Second was the development of a hyperdrive carrying multiple independently movable tetrodes, which allows for the simultaneous monitoring of neural activity from larger populations of neurons from multiple recording locations3,9,10,11,12.
The availability of a reliable and affordable multi-tetrode recording device for small animals is limited. The classic hyperdrive, initially developed by Bruce McNaughton13, has been successfully used for neural recordings in freely behaving rats in many labs in the past two decades9,10,14,15. However, for technical reasons, the original components needed to build the McNaughton drive are now very difficult to obtain and are not compatible with recently improved data acquisition interfaces. The other well accepted design of hyperdrive requires the microdrives to be individually handcrafted, which could yield inconsistent results and consume substantial time12. In order to record neural activity from various brain regions in behaving rats, we developed a new hyperdrive using stereolithographic technology. We sought to satisfy the following requirements: (1) the new hyperdrive must allow precise displacement of tetrodes in the brain and provide stable recording from multiple target regions; (2) the new hyperdrive must be compatible with the magnetic quickclip system recently developed to allow easy connection; and (3) the new hyperdrive can be accurately reproduced with materials easily available. Here, we provide a technique for building the 3D-printable hyperdrive containing eighteen independently movable tetrodes, based upon the McNaughton design. In the protocol, we describe the details of the fabrication process of the new hyperdrive, which we have used successfully to record single-neuron action potentials and local field potentials from the postrhinal and medial entorhinal cortices over weeks in a freely behaving rat during natural foraging tasks.

<table>
	<tbody>
		<tr>
			<td>Welding rod</td>
			<td>Blue Demon</td>
			<td>ER308L-035-01T</td>
			<td>Stainless steel, 0.035&#34; in diameter</td>
		</tr>
		<tr>
			<td>Screw</td>
			<td>McMaster</td>
			<td>91771A060</td>
			<td>Stainless steel, flat head, 0-80&#160;thread,&#160;5/8&#34;&#160;in length</td>
		</tr>
		<tr>
			<td>Screw</td>
			<td>McMaster</td>
			<td>91772A051</td>
			<td>Stainless steel, pan head, 0-80&#160;thread,&#160;5/32&#34;&#160;in length</td>
		</tr>
		<tr>
			<td>Screw</td>
			<td>McMaster</td>
			<td>92196A056</td>
			<td>Stainless steel, socket head, 0-80&#160;thread,&#160;5/16&#34;&#160;in length</td>
		</tr>
		<tr>
			<td>Screw</td>
			<td>McMaster</td>
			<td>92196A055</td>
			<td>Stainless steel, socket head, 0-80&#160;thread,&#160;1/4&#34;&#160;in length</td>
		</tr>
		<tr>
			<td>Screw</td>
			<td>McMaster</td>
			<td>95868A131</td>
			<td>Nylon,&#160; socket head, 2-56&#160;thread,&#160;3/16&#34;&#160;in length, black</td>
		</tr>
		<tr>
			<td>Screw nut</td>
			<td>McMaster</td>
			<td>90730A001</td>
			<td>Stainless steel, narrow hex,&#160; 0-80&#160;thread</td>
		</tr>
		<tr>
			<td>Shoulder screw</td>
			<td>McMaster</td>
			<td>90298A213</td>
			<td>Stainless steel, 8-32 thread, 3/16&#34; in diameter, 1/4&#34; in length</td>
		</tr>
		<tr>
			<td>Cup screw</td>
			<td>McMaster</td>
			<td>92313A105</td>
			<td>Stainless steel, 4-40 thread, 3/16&#34; in length</td>
		</tr>
		<tr>
			<td>Thumb screw</td>
			<td>McMaster</td>
			<td>94323A592</td>
			<td>Nylon, 8-32&#160;thread,&#160;3/8&#34;&#160;in length, black</td>
		</tr>
		<tr>
			<td>Magnet</td>
			<td>Apex</td>
			<td>M3X1MMDI</td>
			<td>Neodymium, 3 mm X 1 mm disc</td>
		</tr>
		<tr>
			<td>Metal tubing</td>
			<td>Small Parts</td>
			<td>B00137QHNS</td>
			<td>Stainless steel, 23 gauge, 0.0253&#34; OD, 0.013&#34; ID, 0.006&#34; wall</td>
		</tr>
		<tr>
			<td>Metal tubing</td>
			<td>New England Small Tube</td>
			<td>Custom-made</td>
			<td>Stainless steel, 30 gauge, 0.012/0.0125&#34; OD, 0.007/0.008&#34; ID, full hard</td>
		</tr>
		<tr>
			<td>Heat-shrink tubing</td>
			<td>McMaster</td>
			<td>7856K72</td>
			<td>0.09&#34; ID before shrinking, blue</td>
		</tr>
		<tr>
			<td>Silicone tubing</td>
			<td>A-M Systems</td>
			<td>807300</td>
			<td>0.040&#34; ID, 0.085&#34; OD</td>
		</tr>
		<tr>
			<td>Polyimide tubing</td>
			<td>A-M Systems</td>
			<td>823400</td>
			<td>0.0045&#34; ID, 0.0005&#34; wall</td>
		</tr>
		<tr>
			<td>Ground wire</td>
			<td>A-M Systems</td>
			<td>791500</td>
			<td>0.005&#34; bare, 0.008&#34; coated, half hard</td>
		</tr>
		<tr>
			<td>Tetrode wire</td>
			<td>California Fine Wire</td>
			<td>Custom-made</td>
			<td>0.0007&#34; in diameter, platinum-iridium (90%-10%), HML and VG coating</td>
		</tr>
		<tr>
			<td>EIB</td>
			<td>Neuralynx</td>
			<td></td>
			<td>EIB-72-QC-Large</td>
		</tr>
		<tr>
			<td>Gold pins</td>
			<td>Neuralynx</td>
			<td></td>
			<td>large EIB pins</td>
		</tr>
		<tr>
			<td>Tap</td>
			<td>Balax</td>
			<td>01302-000</td>
			<td>M1.2 thread size</td>
		</tr>
		<tr>
			<td>Tap</td>
			<td>McMaster</td>
			<td>2522A811</td>
			<td>0-80 thread size, bottoming</td>
		</tr>
		<tr>
			<td>Tap</td>
			<td>McMaster</td>
			<td>2522A771</td>
			<td>0-80 thread size, plug</td>
		</tr>
		<tr>
			<td>Tap</td>
			<td>McMaster</td>
			<td>26955A94</td>
			<td>3/8&#34;-24&#160;thread size, bottoming</td>
		</tr>
		<tr>
			<td>Tap</td>
			<td>McMaster</td>
			<td>2522A713</td>
			<td>2-56&#160;thread size</td>
		</tr>
		<tr>
			<td>Tap</td>
			<td>McMaster</td>
			<td>2522A715</td>
			<td>4-40&#160;thread size</td>
		</tr>
		<tr>
			<td>Tap</td>
			<td>McMaster</td>
			<td>2522A718</td>
			<td>8-32&#160;thread size</td>
		</tr>
		<tr>
			<td>Die</td>
			<td>McMaster</td>
			<td>2576A457</td>
			<td>3/8&#34;-24&#160;thread size, 1&#34; OD</td>
		</tr>
		<tr>
			<td>Drill bit</td>
			<td>McMaster</td>
			<td>30585A82</td>
			<td>Wire gauge&#160;65,&#160;0.035&#34; in diameter</td>
		</tr>
		<tr>
			<td>Drill bit</td>
			<td>McMaster</td>
			<td>30585A83</td>
			<td>Wire gauge&#160;66,&#160;0.033&#34; in diameter</td>
		</tr>
		<tr>
			<td>Drill bit</td>
			<td>McMaster</td>
			<td>30585A87</td>
			<td>Wire gauge&#160;70,&#160;0.028&#34; in diameter</td>
		</tr>
		<tr>
			<td>Drill bit</td>
			<td>McMaster</td>
			<td>30585A88</td>
			<td>Wire gauge&#160;71,&#160;0.026&#34; in diameter</td>
		</tr>
		<tr>
			<td>Drill bit</td>
			<td>McMaster</td>
			<td>30585A91</td>
			<td>Wire gauge&#160;73,&#160;0.024&#34; in diameter</td>
		</tr>
		<tr>
			<td>Drill bit</td>
			<td>McMaster</td>
			<td>8870A23</td>
			<td>3/16&#34;&#160;in diameter</td>
		</tr>
		<tr>
			<td>Dremel disc</td>
			<td>Wagner</td>
			<td>31M</td>
			<td>Diamond coated, 22 mm in diameter, 0.17 mm in thickness</td>
		</tr>
		<tr>
			<td>Steel wire</td>
			<td>Precision Brand</td>
			<td>21212</td>
			<td>0.012&#34; in diameter, full hard</td>
		</tr>
		<tr>
			<td>Steel wire</td>
			<td>Precision Brand</td>
			<td>21007</td>
			<td>0.007&#34; in diameter, full hard</td>
		</tr>
		<tr>
			<td>Steel wire</td>
			<td>A-M Systems</td>
			<td>792700</td>
			<td>0.003&#34; in diameter, half hard</td>
		</tr>
		<tr>
			<td>Super glue</td>
			<td>Loctite</td>
			<td>LT-40640</td>
			<td># 406</td>
		</tr>
		<tr>
			<td>Super glue</td>
			<td>Loctite</td>
			<td>LT-41550</td>
			<td># 415</td>
		</tr>
		<tr>
			<td>Dental acrylic powder&#160;</td>
			<td>Teets</td>
			<td>223-3773</td>
			<td>Coral</td>
		</tr>
		<tr>
			<td>Dental acrylic liquid</td>
			<td>Teets</td>
			<td>223-4003</td>
			<td></td>
		</tr>
	</tbody>
</table>

construction of an improved multi-tetrode hyperdrive for large-scale neural recording in behaving rats

Monitoring the activity patterns of a large population of neurons over many days in awake animals is a valuable technique in the field of systems neuroscience. One key component of this technique consists of the precise placement of multiple electrodes into desired brain regions and the maintenance of their stability. Here, we describe a protocol for the construction of a 3D-printable hyperdrive, which includes eighteen independently adjustable tetrodes, and is specifically designed for in vivo extracellular neural recording in freely behaving rats. The tetrodes attached to the microdrives can either be individually advanced into multiple brain regions along the track, or can be used to place an array of electrodes into a smaller area. The multiple tetrodes allow for simultaneous examination of action potentials from dozens of individual neurons, as well as local field potentials from populations of neurons in the brain during active behavior. In addition, the design provides for simpler 3D drafting software that can easily be modified for differing experimental needs.

We used a newly built hyperdrive to obtain trial results. The drive was equipped with tetrodes constructed from &#248; 17 &#181;m (0.0007&#34;), polyimide-coated platinum-iridium (90%-10%) wire. The tips of the tetrodes were plated in platinum black solution to reduce electrode impedances to between 100 and 200 k&#937; at 1 kHz. The hyperdrive was implanted 4.6 mm left of the midline and 0.5 mm anterior to the transverse sinus on the skull of a 550 g, male Long-Evans rat. Additional groun...

Watch this Scientific Journal Video about Construction of an Improved Multi-Tetrode Hyperdrive for Large-Scale Neural Recording in Behaving Rats at JoVE.com

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

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.

Monitoring the activity patterns of a large population of neurons over many days in awake animals is a valuable technique in the field of systems ...

The overall goal of this procedure is to construct a recording device with multiple independently adjustable electrodes for the examination of brain activity in freely behaving rats. So this method is very exciting because it will help answer several questions related to special navigation, decision making, and other cognitive processes. The main advantage of this hyperdrive is that it provides reliable neuro recording in the brain using materials that are easy to obtain.Although this method was designed to be used specifically with rats, it can be used with any species of similar or larger head sizes such as non-human primates, thereby allowing investigations of many species. Those new to this method might struggle with the nuance involved in the preparation of the steps cause there's a certain level of experience and accuracy that's required to develop these tricks that can make a successful drive. Begin by expanding the holes in the 3D printed core using different sized drill bits.Use a diameter of 0.61 millimeter for the 12 ground wire through holes. For the 18 tetrode through holes, first use a 0.66 millimeter bit and then widen with a 0.71 millimeter bit. A 0.84 millimeter diameter bit is used for the 18 guide rod blind holes.Next, thread the two through holes on top of the core and the remaining eight blind holes with a 0.80 tap. Use a bottoming tap for the blind holes. Create external threads at the base of the core using a 3/8-24 die.Adjust the die properly so the hyperdrive nut will fit over the new threads. Depending on the desired number of ground wires, insert multiple six millimeter long segments of 23 gauge metal tubing into the ground wire holes in the core gluing them if necessary. File the outer ends of the ground wire cannulas until they are flushed with the core and then clean the cannulas with a 0.30 millimeter diameter steel wire.Next, fully insert 18 08015.88 millimeter long flathead screws head down into the slots in the core. Do not bend the screws or damage the threads during this process. Using the rod positioning complex into the core station, position 18 17 millimeter segments of 0.89 millimeter diameter welding rod over the guide rod holes in the core and hammer them down about five millimeters until flushed with the screws.Correct the positions of the welding rods and screws if necessary then tighten the central shoulder screw and the surrounding six screws in the rod positioning complex to secure the outward directions of the rods in the core. Screw the nut onto the core with the rod positioning complex and fit the core into the hyperdrive holder to allow easier positioning under a stereoscope. Fill the slots with dilute dental cement to secure the screws to the core.Fill two to three slots at a time before the dental cement gets too thick. Scrape away any excess dental cement on the core to maintain a proper fit with the shield then allow to air dry for 15 minutes. Next, glue the screws and rods into the core with thin super glue and allow to dry for 15 minutes.Clean and expand the two outer holes in the 3D printed shuttle with drill bits. Use a 0.61 millimeter diameter bit for the smaller hole and a 0.89 millimeter bit for the larger hole. Insert the shuttle bolt into the bolt holder base ensuring the proper orientation.Then close the bolt holder lid. Hold the bolt holder tightly and thread slowly through the hole in the lid with a 0.80 tap. Tap two or three times until smooth.Then insert the shuttle bolt into the shuttle from the side with the smaller opening. Place the shuttle-shuttle bolt complex upside down in the microdrive assembly station base. Next, smooth both ends of a 15 millimeter segment of 23 gauge metal tubing, then position the tubing over the 0.61 millimeter diameter hole guided by the slot in the station lid.Hammer the cannula into the hole until the upper end is flushed with the station lid. Remove the outer half of the upper tip of the cannula with a sanding wheel. Clean the cannula with a 0.30 millimeter diameter metal wire.Then glue the cannula onto the shuttle using thin super glue making sure not to glue the shuttle bolts to the shuttle. Prepare at least 18 microdrives. Test the microdrives on the microdrive rack.Make sure that the shuttle bolt can rotate smoothly in the shuttle and that the entire microdrive moves freely along the length of the threaded rod. To insert guide cannulas into the hyperdrive core, begin by removing the heat shrink tubes and slide a four millimeter segment of silicone tubing along the bundle to the soldered-unsoldered border. Wedge the slit in the hyperdrive spacer to widen the central hole allowing the spacer to slip around the silicone tube.Remove the wedge when the spacer sits at the center of the silicone tube. Next, organize the positions of the guide cannulas in the bundle by placing 10 centimeter long segments of 0.18 millimeter diameter metal wire through each cannula into a specific tetrode hole in the hyperdrive core preventing any crossover of the wires or cannulas in the process. Bend the end of the wires to hold them in place.Push the cannulas through their respective holes in the core being careful to avoid bending or crossing between them until the free end of each cannula is at least two millimeters outside the upper end of the tetrode hole. Secure the spacer by screwing the nut onto the core being careful to prevent the spacer from rotating. Apply a drop of very dilute dental cement from the top of the core onto the junction of the cannulas to secure their relative positions.Cut the guide wires from the soldered end of the bundle and remove them from the cannulas by retracting from the free end. Load the microdrives slowly and carefully onto each threaded rod of the core. Confirm that the 23 gauge microdrive cannula goes into the tetrode hole smoothly, the 30 gauge guide cannula goes into the 23 gauge microdrive cannula smoothly, and the shuttle bolt turn smoothly along the threaded rod.Screw the microdrives down to one to 1.5 millimeters above the lower end of the threaded rods. Then cut 18 pieces of polyamide tubing into 43 millimeter segments which is the length of the guide cannula bundle plus seven millimeters. Clean each tube with a 0.8 millimeter diameter steel wire.Invert the core, insert the polyamide tubes carefully into the guide cannulas from the soldered end and push them all the way in. Then flip the core upright and glue the upper end of the polyamide tube onto the microdrive cannula with thick super glue. Place the core upside down and let the glue dry for 15 minutes.After drying, cut the extra polyamide tubing at the upper end leaving 0.5 to one millimeter outside the microdrive cannula. To assemble the ground wires, first cut lengths of 25 to 30 millimeters from coated steel wire. Then strip two millimeters of the plastic insulation from both tips of the wires and insert one end of each into both sides of a six to eight millimeter long 30 gauge cannula.Flatten this end of each cannula to secure the connection to their respective wires. Finally, insert the round end of the 30 gauge cannula into the upper end of the ground wire cannula in the core and press to make the insertion tight. Then complete assembly of the multi-tetrode hyperdrive according to the instructions in the written protocol.This scatter plot shows the relationship between peak to peak amplitudes of spikes recorded from two electrodes of a tetrode located in the post rhinal cortex. Each dot corresponds to one spike. Clusters of spikes are likely to originate from the same cell.Four clusters are color coded as seen here. The mean spike waveforms from all four tetrode channels of the color coded cells shown in the previous scatter plot are seen here. Traces of local field potential in the theta frequency range recorded simultaneously from four different tetrodes located in the medial entorhinal cortex when the rat was freely foraging are seen here.While attempting this procedure, it's important to work with precision throughout the entire procedure to ensure that all parts fit together properly. Also use care and wear proper PPE when working with the demo tool to avoid injury. After watching this video, you should have a good understanding of how to construct these improved hyperdrives carrying multiple tetrodes for chronic neuro recordings in behaving rats.

construction-an-improved-multi-tetrode-hyperdrive-for-large-scale

Research

JoVE Journal

Neuroscience

11.1K Views.  Baylor College of Medicine. The overall goal of this procedure is to construct a recording device with multiple independently adjustable electrodes for the examination of brain activity in freely behaving rats. So this method is very exciting because it will help answer several questions related to special navigation, decision making, and other cognitive processes. The main advantage of this hyperdrive is that it provides reliable neuro recording in the brain using materials that are easy to obtain.Although this ...