This work was supported by the National Institute of Health (RO1 NS120945, R37NS119012 to JK) and the UVA Brain Institute.

The present work is approved by the University of Virginia Animal Care and Use Committee. C57Bl/6 mice of both sexes (7-12 weeks) were used for the experiments. The animals were maintained on a 12 h light/12 h dark cycle and had ad libitum access to food and water.
1. Microelectrode construction
<ol>
	<li>To construct the microelectrodes, use 50 &#181;m (diameter) diamel-coated nickel-chromium wire (see Table of Materials). Tape one end of the wire at the back of the platform and wrap the wire three times around the nearest knob on the platform (Figure 1A,C). 
	NOTE: An acrylic platform with two knobs (2 x 5 inches) was used here, but any platform can be used.
	<ol>
		<li>Stretch the wire around the farthest second knob to make two loops between the knobs. Wrap the wire three more times around the first knob to fix the wire in place and tape the end again at the back of the platform. 
		NOTE: After the wires are separated (steps 1.2-1.3.1), there must be two wires on each side (four wires in total, Figure 1B).</li>
	</ol>
	</li>
	<li>Place the tension bars under the wires with the tape wrapped around them (sticky side up) (Figure 1C). 
	NOTE: Triangular acrylic pieces were used for the tension bars, with tape wrapped around them (sticky side outside to attach the wires). The sticky side of the tape outside of the tension bars will keep the wires in place to adjust the distance between them. The tension bars must be ~2.5 cm away from the knobs, and the wires must not be loose.</li>
	<li>Using a microscope and fine forceps, make either a 3 mm or 4.5 mm gap between the wires (3 mm gap between the wires to make cortical (Ctx) - ventrolateral thalamic nucleus (VL) microelectrodes; 4.5 mm gap to make striatal (Str) - nigral (SNR) microelectrodes) (Figure 1B).
	<ol>
		<li>If magnification is used on the microscope, ensure to calculate and adjust for the difference in magnification and the actual distance between the wires. 
		NOTE: If microelectrodes are constructed for structures other than those used here, the distance between the wires needs to be adjusted to the stereotaxic distance between the structures. Figure 2B provides an example of how the wires will be organized; accordingly, the stereotaxic coordinates for other structures must be adjusted.</li>
	</ol>
	</li>
	<li>Cut four small pieces of plastic (0.5 mm thick) ~6 mm (width) x 3 mm (height) (Figure 1C). 
	NOTE: Any plastic pieces can be used as long as they are 0.5 mm thick; here, square tubing was used in which the pins were sold (Pins, see Table of Materials). If a different thickness is used, please add more or fewer pieces of plastic to fit the required stereotaxic coordinates.</li>
	<li>Apply glue (see Table of Materials) on the plastic and place them on the wires (Figure 1C). Place plastic pieces ~1.0 cm away from the middle of the wire, which is 1.0 cm away from the tension bar. Remove the excess of superglue with a cotton swab.</li>
	<li>After the superglue dries, cut the wires using fine scissors, in the order indicated in Figure 1C.</li>
	<li>Cut four 7 mm glass tubes using a commercially available kit (see Table of Materials) and insert the electrode wires into the glass tubes as indicated in Figure 2A.
	<ol>
		<li>Insert VL and SNR electrode pairs into the glass tubes. 
		NOTE: Only the wires for deep structures need to be inserted into the glass tubes to support surgical implantation. Ensure not to insert cortical electrodes into the glass tube.</li>
	</ol>
	</li>
	<li>Put the glue at the base of the glass tubes to connect them to the plastic. Wait some time until the glue dries.</li>
	<li>Cut the glass tubes and wires using a scalpel as indicated in Table 1; ensure that the lengths of the microelectrodes are correct. If the microelectrodes target different structures, adjust the cutting distance according to the required stereotaxic coordinates.</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/63633/63633fig01.jpg" /> 
Figure 1: Schematic of the microelectrode construction. (A) Set up of wires on the platform with tension bars below the wires. (B) The gap between the wires. (C) Four pieces of plastic are glued to the wires. <a href="https://www.jove.com/files/ftp_upload/63633/63633fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td></td>
			<td>Ctx</td>
			<td>Str</td>
			<td>VL</td>
			<td>SNR</td>
		</tr>
		<tr>
			<td>AP (Anterior/Posterior)</td>
			<td>2.2</td>
			<td>1.2</td>
			<td>-1.3</td>
			<td>-3.3</td>
		</tr>
		<tr>
			<td>ML (Medial/Lateral)</td>
			<td>1.8</td>
			<td>1.5</td>
			<td>1</td>
			<td>1.5</td>
		</tr>
		<tr>
			<td>DV (Dorsal/Ventral)</td>
			<td>0.5</td>
			<td>3.5</td>
			<td>4</td>
			<td>4.75</td>
		</tr>
		<tr>
			<td>Electrode length</td>
			<td>4</td>
			<td>4.75</td>
			<td>5.25</td>
			<td>6</td>
		</tr>
	</tbody>
</table>
Table 1: Stereotaxic implantation coordinates and dimensions of the microelectrodes.
2. Microelectrode array assembly
<ol>
	<li>Use the glue to attach plastics in the desired order of target regions. An example for cortical, thalamic, striatal, and nigral electrodes is shown in Figure 2B,C.
	<ol>
		<li>Place Ctx-VL electrode pair face down (side with electrode wires has to face down) and connect two 6 mm x 3 mm empty pieces of plastic on top with glue.</li>
		<li>On top of the three pieces of plastic, place the second Ctx-VL electrode pair with the electrodes facing upwards (use a microscope and ensure that the VL electrodes are aligned). 
		NOTE: Alignment of bilateral electrodes (here, the alignment of left and right VL electrodes) is essential to target desired bilateral structures appropriately.</li>
		<li>Use the glue to attach the SNR electrodes on top with the SNR electrodes 2.0 mm away from the VL electrodes and ~5.0 mm away from the cortical electrodes (the SNR electrode wires have to face upwards).</li>
		<li>Repeat step 2.1.3. for the other side (the SNR electrode wires have to face outside of the microelectrode array).</li>
	</ol>
	</li>
	<li>Apply epoxy resin around the plastic to bind the electrodes together. Avoid putting epoxy resin on the electrodes.</li>
	<li>Take a thick wire and make a loop on one end. Dip the loop in the epoxy solution and place it on the plastic, ensuring the thick wire is lying flat (Figure 2D) so that for the next steps, this wire could be used as a handle. Wait until the electrodes are fully dry.</li>
	<li>Cut the wires to 2 cm, as shown in Figure 2E.</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/63633/63633fig02v2.jpg" /> 
Figure 2: Microelectrode construction and dimensions. (A) Four pairs of electrodes formed after the wires were cut with scissors, as indicated in Figure 1C (2 pairs of Ctx-VL electrodes and 2 pairs of Str-SNR electrodes). Insert deep structure electrodes (VL and SNR) into the glass tubes and glue their bases to plastic (red dots). (B) Top view: The electrode pairs from (A) are glued in a stack to create the microelectrode core. Red lines indicate glue lines. (C) Front side view of (B). (D) The thick wire was attached to the microelectrodes. (E) The wires are grouped as indicated, and the isolated ends are scraped off and cut into 2 cm. <a href="https://www.jove.com/files/ftp_upload/63633/63633fig02largev2.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
3. Microelectrode connection to the headset
<ol>
	<li>Group the wires as indicated in Figure 2E and scrape away 1 mm of the isolated ends with a scalpel.</li>
	<li>Bend the cortical electrodes as shown in Figure 3A. Separate the wires as shown in Figure 3B. Using fine forceps, make a loop at the end of each wire (Figure 3B).</li>
	<li>Hold a 10-pin headset with a hemostat (see Table of Materials) and use the wooden end of a cotton swab to apply minimal amounts of flux on the pins (Figure 3C). Ensure not to put flux outside the pins to prevent short-circuit among the pins.</li>
	<li>Using the wooden end of a cotton swab, apply flux to the wire loops.</li>
	<li>Solder the wire loops to the 10-pin headset as shown in Figure 3C. After soldering, dry the headset to prevent short-circuit among the pins.</li>
	<li>Take a thin wire (0.005-0.008 inch) for the reference and ground wires and strip off the plastic from one end. Make a loop on the other end of the wire.</li>
	<li>Solder the stripped side of the reference and ground wires to their respective pins (Figure 3A,C).</li>
	<li>Holding on the thick wire (Figure 2D), apply cranioplasty cement around the microelectrodes, especially where the wires connect to the pins. Avoid touching the actual electrode ends with the cement.</li>
	<li>After the cement dries, put epoxy resin at the base of the glass tubes, striatal microelectrode wires, and the whole electrode. Avoid touching the actual electrode ends with epoxy resin. Wait until the electrodes are fully dry.</li>
	<li>The electrodes are ready. Drill holes in the mouse&#39;s skull (as per the required stereotaxic coordinates) using a dental drill and implant the headset as shown in Figure 3D by lowering the headset with microelectrodes facing the skull and the appropriate holes. The headset could be attached to the stereotaxic arm for support during the implantation.</li>
</ol>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/63633/63633fig03.jpg" /> 
Figure 3: Microelectrode implantation. (A) The cortical electrodes are bent as indicated. (B) The wires are separated to make loops at the ends. (C) The flux (at the red dots) and looped wires are soldered to the 10-pin headset, ensuring that each wire goes to its appropriate pin. (D) The headset is implanted to record LFPs. <a href="https://www.jove.com/files/ftp_upload/63633/63633fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
4. Marking electrode location after recordings
<ol>
	<li>At the end of the LFP recordings, confirm the correct position of the electrodes in the target region by applying a current at the electrode tips to make a lesion and waiting for 30 min before perfusing the mouse. 
	NOTE: Lesion settings to confirm the location of the electrode tips: Single burst, 40 &#181;A, 0.75 ms monophasic square wave pulse, 50 Hz, 30 s.</li>
	<li>Anesthetize the mice with isoflurane (until the mouse fell asleep) and perfuse10&#160;transcardially with 4% paraformaldehyde (PFA) in 0.1 M sodium phosphate buffer. Section the brains (40 &#181;m thick) on a cryostat (see Table of Materials) and stain with DAPI (0.02% in PBS). Confirm the correct location of the electrodes by the presence of the electrode tip lesions as shown in Figure 4B,C. 
	NOTE: The percentage of the isoflurane needs to be applied following the individual institution&#39;s guidelines.</li>
</ol>
5. Measuring the electrode resistance
<ol>
	<li>Measure the resistance of the electrodes and check the short-circuit among the electrodes using a multi-range ohmmeter (see Table of Materials). Set the resistance scale at R x 10,000, indicating that a unit deflection in the pointer corresponds to 1 k&#937; resistance. 2 cm long electrodes need to have 60-70 k&#937; resistance.</li>
	<li>Customize the headset by taking ten individual pins (see Table of Materials). Solder each pin with a thin, multi-stranded copper wire in a cable.
	<ol>
		<li>Press-fit the soldered pins with their corresponding cable tails into the 10-pin double-row mating socket (matching sockets). Press-fit the open-ended pins of the mating socket into the LFP headset. In this way, each LFP electrode has a designated cable wire in the assembly.</li>
	</ol>
	</li>
	<li>Dip the tip of each LFP electrode (the resistance of which is to be measured) into 0.9% NaCl saline solution (NaCl concentration in the blood). Connect the cable wire end that corresponds to the LFP electrode to the positive terminal of the ohmmeter.
	<ol>
		<li>Use a low resistance ( &#820;100 &#937;) wire with one side in the saline water and the other side as the open end. Connect the open end of the low-resistance wire to the ground of the ohmmeter pointer. 
		NOTE: This arrangement completes the circuit and prompts a deflection of the ohmmeter pointer.</li>
	</ol>
	</li>
	<li>Ensure that there is no electrical connection between any two electrodes on the headset. Check the electrical insulation of pairwise LFP electrodes (ground: one cable corresponds to one electrode; positive: another cable corresponds to another electrode). Discard the electrodes if any deflection is observed in this case.</li>
</ol>

<ol>
	<li>Buzs&#225;ki, G., Anastassiou, C. A., Koch, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+origin+of+extracellular+fields+and+currents-EEG,+ECoG,+LFP+and+spikes.">The origin of extracellular fields and currents-EEG, ECoG, LFP and spikes.</a> Nature Reviews Neuroscience. 13, 407-420 (2012).</li><li>Hubel, D. H., Wiesel, T. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Receptive+fields+of+single+neurones+in+the+cat's+striate+cortex.">Receptive fields of single neurones in the cat's striate cortex.</a> The Journal of Physiology. 148 (3), 574-591 (1959).</li><li>O'Keefe, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Place+units+in+the+hippocampus+of+the+freely+moving+rat.">Place units in the hippocampus of the freely moving rat.</a> Experimental Neurology. 51 (1), 78-109 (1976).</li><li>Fyhn, M., Molden, S., 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=Spatial+representation+in+the+entorhinal+cortex.">Spatial representation in the entorhinal cortex.</a> Science. 305 (5688), 1258-1264 (2004).</li><li>Buzs&#225;ki, 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> Nature Neuroscience. 7, 446-451 (2004).</li><li>Buckmaster, P. S., Edward Dudek, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+intracellular+analysis+of+granule+cell+axon+reorganization+in+epileptic+rats.">In vivo intracellular analysis of granule cell axon reorganization in epileptic rats.</a> Journal of Neurophysiology. 81 (2), 712-721 (1999).</li><li>Driscoll, N., 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=Multimodal+in+vivo+recording+using+transparent+graphene+microelectrodes+illuminates+spatiotemporal+seizure+dynamics+at+the+microscale.">Multimodal in vivo recording using transparent graphene microelectrodes illuminates spatiotemporal seizure dynamics at the microscale.</a> Communications Biology. 4, 1-14 (2021).</li><li>Roy, D. 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=Memory+retrieval+by+activating+engram+cells+in+mouse+models+of+early+Alzheimer's+disease.">Memory retrieval by activating engram cells in mouse models of early Alzheimer's disease.</a> Nature. 531, 508-512 (2016).</li><li>Igarashi, K. M., Lu, L., Colgin, L. L., Moser, M. B., Moser, E. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coordination+of+entorhinal-hippocampal+ensemble+activity+during+associative+learning.">Coordination of entorhinal-hippocampal ensemble activity during associative learning.</a> Nature. 510, 143-147 (2014).</li><li>Gage, G. J., Kipke, D. R., Shain, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whole+animal+perfusion+fixation+for+rodents.">Whole animal perfusion fixation for rodents.</a> Journal of Visualized Experiments. (65), e3564 (2012).</li><li>Brodovskaya, A., Shiono, S., Kapur, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activation+of+the+basal+ganglia+and+indirect+pathway+neurons+during+frontal+lobe+seizures.">Activation of the basal ganglia and indirect pathway neurons during frontal lobe seizures.</a> Brain. 144 (7), 2074-2091 (2021).</li><li>Ren, X., Brodovskaya, A., Hudson, J. L., Kapur, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Connectivity+and+neuronal+synchrony+during+seizures.">Connectivity and neuronal synchrony during seizures.</a> The Journal of Neuroscience. 41 (36), 7623-7635 (2021).</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> Journal of Visualized Experiments. (77), e50470 (2013).</li></ol>

The authors have nothing to disclose.

Historically, microelectrode arrays have been extensively used to record neuronal activity from a specific brain region of interest2,3,4,5,6,7,8,9,13. However, our easy microelectrode design allows recording from multiple ...

Local field potentials (LFPs) are the electric potentials recorded from the extracellular space in the brain. They are generated by ion concentration imbalances outside of neurons and represent the activity of a small, localized population of neurons, allowing to precisely monitor the activity of a specific brain region compared to the macroscale EEG recordings1. As an estimate, the LFP microelectrodes separated by 1 mm correspond to two completely different populations of neurons. While EEG signal is filtered by brain tissue, cerebrospinal fluid, skull, muscle, and skin, LFP signal is a reliable marker of local neuronal activity1.
Researchers often need to simultaneously record LFPs from several brain structures, but commercially available microelectrode arrays often do not offer such flexibility. Here, the present protocol describes fully customizable, easily constructed microelectrodes to simultaneously record LFPs from any desired brain region at different depths. Although LFPs have extensively been used to record the neuronal activity of a specific brain region2,3,4,5,6,7,8,9, the current easy customizable design allows recording LFPs from any multiple superficial or deep brain regions11,12. The protocol can also be modified to construct any desired microelectrode array by determining stereotaxic coordinates of the brain regions and assembling the array accordingly. These microelectrodes with a 10 kHz sampling rate and 60-70 k&#8486; resistance (2 cm length) allow us to record LFPs with millisecond precision. The data can then be amplified by a 16-channel amplifier, filtered (low pass 1 Hz, high pass 5 kHz), and digitized.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Amplifier 16-Channel</td>
			<td>A-M Systems</td>
			<td>Model 3600</td>
			<td>Amplifier</td>
		</tr>
		<tr>
			<td>Cranioplasty cement</td>
			<td>Coltene</td>
			<td>Perm Reeline/Repair Resin Type II Class I Shade - Clear</td>
			<td>Cement to hold microelectrodes</td>
		</tr>
		<tr>
			<td>Cryostat Microtome</td>
			<td>Precisionary</td>
			<td>CF-6100</td>
			<td>To slice brain</td>
		</tr>
		<tr>
			<td>Diamel-coatednickel-chromium wire</td>
			<td>Johnson Matthey Inc.</td>
			<td>50 &#181;m</td>
			<td>Microelectrode wire</td>
		</tr>
		<tr>
			<td>Dremel</td>
			<td>Dremel</td>
			<td>300 Series</td>
			<td>To drill holes in mouse skull</td>
		</tr>
		<tr>
			<td>Epoxy</td>
			<td>CEC Corp</td>
			<td>C-POXY 5</td>
			<td>Fast setting adhesive</td>
		</tr>
		<tr>
			<td>Hemostat</td>
			<td>Any</td>
			<td></td>
			<td>To hold the headset</td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>Any</td>
			<td></td>
			<td>To hold microelectrodes</td>
		</tr>
		<tr>
			<td>Light microscope</td>
			<td>Nikon</td>
			<td>SMZ-10</td>
			<td>To see alignment</td>
		</tr>
		<tr>
			<td>Ohmmeter</td>
			<td>Any</td>
			<td></td>
			<td>To measurre resistance</td>
		</tr>
		<tr>
			<td>Pins (Headers and matching Sockets)</td>
			<td>Mill-Max</td>
			<td>Interconnects, 833 series, 2 mm grid gull wing surface mount headers and sockets</td>
			<td>To attach microelectrodes to</td>
		</tr>
		<tr>
			<td>Polymicro Tubing Kit</td>
			<td>Neuralynx</td>
			<td>ID 100 &#177; 04 &#181;m, OD 164 &#177; 06 &#181;m, coating thickness 12 &#181;m</td>
			<td>Glass tubes</td>
		</tr>
		<tr>
			<td>Pulse Stimulator</td>
			<td>A-M Systems</td>
			<td>Model 2100</td>
			<td>To mark the microelectrode location at the end of the recordings</td>
		</tr>
		<tr>
			<td>Scissors</td>
			<td>Any</td>
			<td></td>
			<td>To cut microelectrodes</td>
		</tr>
		<tr>
			<td>Superglue</td>
			<td>Gorilla</td>
			<td></td>
			<td>Adhesive</td>
		</tr>
		<tr>
			<td>Thick wire 0.008 in. &#8211; 0.011 in.</td>
			<td>A-M Systems</td>
			<td>791900</td>
			<td>Tick wire to hold the microelectrode array</td>
		</tr>
		<tr>
			<td>Thin wire 0.005 in. - 0.008 in.</td>
			<td>A-M Systems</td>
			<td>791400</td>
			<td>Thin wire for reference and ground</td>
		</tr>
	</tbody>
</table>

construction of local field potential microelectrodes for in vivo recordings from multiple brain structures simultaneously

Researchers often need to record local field potentials (LFPs) simultaneously from several brain structures. Recording from multiple desired brain regions requires different microelectrode designs, but commercially available microelectrode arrays often do not offer such flexibility. Here, the present protocol outlines the straightforward design of custom-made microelectrode arrays to record LFPs from multiple brain structures simultaneously at different depths. This work describes the construction of the bilateral cortical, striatal, ventrolateral thalamic, and nigral microelectrodes as an example. The outlined design principle offers flexibility, and the microelectrodes can be modified and customized to record LFPs from any structure by calculating stereotaxic coordinates and quickly changing the construction accordingly to target different brain regions in either freely moving or anesthetized mice. The microelectrode assembly requires standard tools and supplies. These custom microelectrode arrays allow investigators to easily design microelectrode arrays in any configuration to track neuronal activity, providing LFP recordings with millisecond resolution.

In this work, the LFP microelectrodes were used to map the seizure spread through the basal ganglia11. Simultaneous LFP recordings were performed from the right premotor cortex (where the seizure focus was) and the left VL, striatum, and SNR (Figure 4). Seizure start was identified as deflection of the voltage trace at least twice the baseline (Figure 4A, red arrow). The power spectrum plot11&#160;shows frequency d...

Watch this Scientific Journal Video about Construction of Local Field Potential Microelectrodes for in vivo Recordings from Multiple Brain Structures Simultaneously at JoVE.com

Construction of Local Field Potential Microelectrodes for in vivo Recordings from Multiple Brain Structures Simultaneously

The present protocol describes the construction of custom-made microelectrode arrays to record local field potentials in vivo from multiple brain structures simultaneously.

Construction of Local Field Potential Microelectrodes for in vivo Recordings from Multiple Brain Structures Simultaneously

Researchers often need to record local field potentials (LFPs) simultaneously from several brain structures. Recording from multiple desired brain regions ...

construction-local-field-potential-microelectrodes-for-vivo

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2.8K Views.  University of Virginia. The present protocol describes the construction of custom-made microelectrode arrays to record local field potentials in vivo from multiple brain structures simultaneously.

Video: Construction of Local Field Potential Microelectrodes for in vivo Recordings from Multiple Brain Structures Simultaneously

Single-unit In vivo Recordings from the Optic Chiasm of Rat

Information about the visual world is transmitted to the brain in sequences of action potentials in retinal ganglion cell axons that make up the optic nerve. In vivo recordings of ganglion cell spike trains in several animal models have revealed much of what is known about how the early visual system processes and encodes visual information. However, such recordings have been rare in one of the most common animal models, the rat, possibly owing to difficulty in detecting spikes fired by small diameter axons. The many retinal disease models involving rats motivate a need for characterizing the functional properties of ganglion cells without disturbing the eye, as with intraocular or in vitro recordings. Here, we demonstrate a method for recording ganglion cell spike trains from the optic chiasm of the anesthetized rat. We first show how to fabricate tungsten-in-glass electrodes that can pick up electrical activity from single ganglion cell axons in rat. The electrodes outperform all commercial ones that we have tried. We then illustrate our custom-designed stereotaxic system for in vivo visual neurophysiology experiments and our procedures for animal preparation and reliable and stable electrode placement in the optic chiasm.

Single-unit In vivo Recordings from the Optic Chiasm of Rat

Retinal ganglion cells transmit visual information from the eye to the brain with sequences of action potentials. Here, we demonstrate how to record the action potentials of single ganglion cells in vivo from anesthetized rats.

Information about the visual world is transmitted to the brain in sequences of action potentials in retinal ganglion cell axons that make up the optic ...

Functional Neuroimaging Using Ultrasonic Blood-brain Barrier Disruption and Manganese-enhanced MRI

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains technically challenging. One approach, Activation-Induced Manganese-enhanced MRI (AIM MRI), has been used successfully to map neuronal activity in rodents 1-5. In AIM MRI, Mn2+ acts a calcium analog and accumulates in depolarized neurons 6,7. Because Mn2+ shortens the T1 tissue property, regions of elevated neuronal activity will enhance in MRI. Furthermore, Mn2+ clears slowly from the activated regions; therefore, stimulation can be performed outside the magnet prior to imaging, enabling greater experimental flexibility. However, because Mn2+ does not readily cross the blood-brain barrier (BBB), the need to open the BBB has limited the use of AIM MRI, especially in mice.
One tool for opening the BBB is ultrasound. Though potentially damaging, if ultrasound is administered in combination with gas-filled microbubbles (i.e., ultrasound contrast agents), the acoustic pressure required for BBB opening is considerably lower. This combination of ultrasound and microbubbles can be used to reliably open the BBB without causing tissue damage 8-11.
Here, a method is presented for performing AIM MRI by using microbubbles and ultrasound to open the BBB. After an intravenous injection of perflutren microbubbles, an unfocused pulsed ultrasound beam is applied to the shaved mouse head for 3 minutes. For simplicity, we refer to this technique of BBB Opening with Microbubbles and UltraSound as BOMUS 12. Using BOMUS to open the BBB throughout both cerebral hemispheres, manganese is administered to the whole mouse brain. After experimental stimulation of the lightly sedated mice, AIM MRI is used to map the neuronal response.
To demonstrate this approach, herein BOMUS and AIM MRI are used to map unilateral mechanical stimulation of the vibrissae in lightly sedated mice 13. Because BOMUS can open the BBB throughout both hemispheres, the unstimulated side of the brain is used to control for nonspecific background stimulation. The resultant 3D activation map agrees well with published representations of the vibrissae regions of the barrel field cortex 14. The ultrasonic opening of the BBB is fast, noninvasive, and reversible; and thus this approach is suitable for high-throughput and/or longitudinal studies in awake mice.

A technique is described for broadly opening the blood-brain barrier in the mouse using microbubbles and ultrasound. Using this technique, manganese can be administered to the mouse brain. Because manganese is an MRI contrast agent that accumulates in depolarized neurons, this approach enables imaging of neuronal activity.

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains ...

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 ...

Paired Whole Cell Recordings in Organotypic Hippocampal Slices

Pair recordings involve simultaneous whole cell patch clamp recordings from two synaptically connected neurons, enabling not only direct electrophysiological characterization of the synaptic connections between individual neurons, but also pharmacological manipulation of either the presynaptic or the postsynaptic neuron. When carried out in organotypic hippocampal slice cultures, the probability that two neurons are synaptically connected is significantly increased. This preparation readily enables identification of cell types, and the neurons maintain their morphology and properties of synaptic function similar to that in native brain tissue. A major advantage of paired whole cell recordings is the highly precise information it can provide on the properties of synaptic transmission and plasticity that are not possible with other more crude techniques utilizing extracellular axonal stimulation. Paired whole cell recordings are often perceived as too challenging to perform. While there are challenging aspects to this technique, paired recordings can be performed by anyone trained in whole cell patch clamping provided specific hardware and methodological criteria are followed. The probability of attaining synaptically connected paired recordings significantly increases with healthy organotypic slices and stable micromanipulation allowing independent attainment of pre- and postsynaptic whole cell recordings. While CA3-CA3 pyramidal cell pairs are most widely used in the organotypic slice hippocampal preparation, this technique has also been successful in CA3-CA1 pairs and can be adapted to any neurons that are synaptically connected in the same slice preparation. In this manuscript we provide the detailed methodology and requirements for establishing this technique in any laboratory equipped for electrophysiology.

Pair recordings are simultaneous whole cell patch clamp recordings from two synaptically connected neurons, enabling precise electrophysiological and pharmacological characterization of the synapses between individual neurons. Here we describe the detailed methodology and requirements for establishing this technique in organotypic hippocampal slice cultures in any laboratory equipped for electrophysiology.

Pair recordings involve simultaneous whole cell patch clamp recordings from two synaptically connected neurons, enabling not only direct ...

Electrophysiological Method for Whole-cell Voltage Clamp Recordings from Drosophila Photoreceptors

Whole-cell voltage clamp recordings from Drosophila melanogaster photoreceptors have revolutionized the field of invertebrate visual transduction, enabling the use of D. melanogaster molecular genetics to study inositol-lipid signaling and Transient Receptor Potential (TRP) channels at the single-molecule level. A handful of labs have mastered this powerful technique, which enables the analysis of the physiological responses to light under highly controlled conditions. This technique allows control over the intracellular and extracellular media; the membrane voltage; and the fast application of pharmacological compounds, such as a variety of ionic or pH indicators, to the intra- and extracellular media. With an exceptionally high signal-to-noise ratio, this method enables the measurement of dark spontaneous and light-induced unitary currents (i.e.&#160;spontaneous and quantum bumps) and macroscopic Light-induced Currents (LIC) from single D. melanogaster photoreceptors. This protocol outlines, in great detail, all the key steps necessary to perform this technique, which includes both electrophysiological and optical recordings. The fly retina dissection procedure for the attainment of intact and viable ex vivo isolated ommatidia in the bath chamber is described. The equipment needed to perform whole-cell and fluorescence imaging measurements are also detailed. Finally, the pitfalls in using this delicate preparation during extended experiments are explained.

Electrophysiological Method for Whole-cell Voltage Clamp Recordings from Drosophila Photoreceptors

Whole-cell recordings from Drosophila melanogaster photoreceptors enable the measurement of spontaneous dark bumps, quantum bumps, macroscopic responses to light, and current-voltage relationships under various conditions. In combination with D. melanogaster genetic manipulation tools, this method enables the study of the ubiquitous inositol-lipid signaling pathway and its target, the TRP channel.

Whole-cell voltage clamp recordings from Drosophila melanogaster photoreceptors have revolutionized the field of invertebrate visual transduction, ...

Acute In Vivo Electrophysiological Recordings of Local Field Potentials and Multi-unit Activity from the Hyperdirect Pathway in Anesthetized Rats

Converging evidence shows that many neuropsychiatric diseases should be understood as disorders of large-scale neuronal networks. To better understand the pathophysiological basis of these diseases, it is necessary to precisely characterize in which way the processing of information is disturbed between the different neuronal parts of the circuit. Using extracellular in vivo electrophysiological recordings, it is possible to accurately delineate neuronal activity within a neuronal network. The application of this method has several advantages over alternative techniques, e.g., functional magnetic resonance imaging and calcium imaging, as it allows a unique temporal and spatial resolution and does not rely on genetically engineered organisms. However, the use of extracellular in vivo recordings is limited since it is an invasive technique that cannot be universally applied. In this article, a simple and easy to use method is presented with which it is possible to simultaneously record extracellular potentials such as local field potentials and multiunit activity at multiple sites of a network. It is detailed how a precise targeting of subcortical nuclei can be achieved using a combination of stereotactic surgery and online analysis of multi-unit recordings. Thus, it is demonstrated, how a complete network such as the hyperdirect cortico-basal ganglia loop can be studied in anesthetized animals in vivo.

Acute In Vivo Electrophysiological Recordings of Local Field Potentials and Multi-unit Activity from the Hyperdirect Pathway in Anesthetized Rats

In this study, the methodology is presented on how to perform multi-site in vivo electrophysiological recordings from the hyperdirect pathway under urethane anesthesia.

Converging evidence shows that many neuropsychiatric diseases should be understood as disorders of large-scale neuronal networks. To better understand the ...

Concurrent Recording of Co-localized Electroencephalography and Local Field Potential in Rodent

Although electroencephalography (EEG) is widely used as a non-invasive technique for recording neural activities of the brain, our understanding of the neurogenesis of EEG is still very limited. Local field potentials (LFPs) recorded via a multi-laminar microelectrode can provide a more detailed account of simultaneous neural activity across different cortical layers in the neocortex, but the technique is invasive. Combining EEG and LFP measurements in a pre-clinical model can greatly enhance understanding of the neural mechanisms involved in the generation of EEG signals, and facilitate the derivation of a more realistic and biologically accurate mathematical model of EEG. A simple procedure for acquiring concurrent and co-localized EEG and multi-laminar LFP signals in the anesthetized rodent is presented here. We also investigated whether EEG signals were significantly affected by a burr hole drilled in the skull for the insertion of a microelectrode. Our results suggest that the burr hole has a negligible impact on EEG recordings.

This protocol describes a simple method for concurrent recording of co-localized electroencephalography (EEG) and multi-laminar local field potential in an anesthetized rat. A burr hole drilled in the skull for the insertion of a microelectrode is shown to produce negligible distortion of the EEG signal.

Although electroencephalography (EEG) is widely used as a non-invasive technique for recording neural activities of the brain, our understanding of the ...

Simultaneous Recordings of Cortical Local Field Potentials, Electrocardiogram, Electromyogram, and Breathing Rhythm from a Freely Moving Rat

Monitoring the physiological dynamics of the brain and peripheral tissues is necessary for addressing a number of questions about how the brain controls body functions and internal organ rhythms when animals are exposed to emotional challenges and changes in their living environments. In general experiments, signals from different organs, such as the brain and the heart, are recorded by independent recording systems that require multiple recording devices and different procedures for processing the data files. This study describes a new method that can simultaneously monitor electrical biosignals, including tens of local field potentials in multiple brain regions, electrocardiograms that represent the cardiac rhythm, electromyograms that represent awake/sleep-related muscle contraction, and breathing signals, in a freely moving rat. The recording configuration of this method is based on a conventional micro-drive array for cortical local field potential recordings in which tens of electrodes are accommodated, and the signals obtained from these electrodes are integrated into a single electrical board mounted on the animal's head. Here, this recording system was improved so that signals from the peripheral organs are also transferred to an electrical interface board. In a single surgery, electrodes are first separately implanted into the appropriate body parts and the target brain areas. The open ends of all of these electrodes are then soldered to individual channels of the electrical board above the animal's head so that all of the signals can be integrated into the single electrical board. Connecting this board to a recording device allows for the collection of all of the signals into a single device, which reduces experimental costs and simplifies data processing, because all data can be handled in the same data file. This technique will aid the understanding of the neurophysiological correlates of the associations between central and peripheral organs.

This study introduces a method for the simultaneous recording of local field potentials in the brain, electrocardiograms, electromyograms, and breathing signals of a freely moving rat. This technique, which reduces experimental costs and simplifies data analysis, will contribute to the understanding of the interactions between the brain and peripheral organs.

Monitoring the physiological dynamics of the brain and peripheral tissues is necessary for addressing a number of questions about how the brain controls ...

In Vivo Electrophysiological Measurement of Compound Muscle Action Potential from the Forelimbs in Mouse Models of Motor Neuron Degeneration

Assessing the functionality of the nerve axon provides detailed information on the progression of neuromuscular disorders. Electrophysiological recordings provide a sensitive approach to measure nerve conduction in humans and rodent models. To broaden the technical possibilities for electromyography in mice, the measurement of compound muscle action potentials (CMAPs) from the brachial plexus nerve in the forelimb using needle electrodes is described here. CMAP recordings after stimulating the sciatic nerve in hindlimbs have been previously described. The newly introduced method here allows for the evaluation of the nerve conductivity at an additional site, and thus provides a more profound overview of the neuromuscular functionality. The technique provides information on both the relative number of functional axons and the myelination level. Thereby, this method can be applied to assess both axonal diseases as well as demyelinating conditions. This minimally invasive method does not require extraction of the nerve and therefore it is suitable for repeated measurements for longitudinal follow-up in the same animal. Similar recordings are performed in clinical setups to emphasize the translational relevance of the method.

In Vivo Electrophysiological Measurement of Compound Muscle Action Potential from the Forelimbs in Mouse Models of Motor Neuron Degeneration

The measurement of nerve conduction is a useful tool to assess mouse models of neurodegeneration but it is frequently only applied to stimulate the sciatic nerve in hindlimbs. Here, we describe a technique to measure compound muscle action potential (CMAP) in vivo in the mouse forelimb muscles innervated by the brachial plexus.

Assessing the functionality of the nerve axon provides detailed information on the progression of neuromuscular disorders. Electrophysiological recordings ...

Evaluation of Hemisphere Lateralization with Bilateral Local Field Potential Recording in Secondary Motor Cortex of Mice

This article demonstrates complete, detailed procedures for both in vivo bilateral recording and analysis of local field potential (LFP) in the cortical areas of mice, which are useful for evaluating possible laterality deficits, as well as for assessing brain connectivity and coupling of neural network activities in rodents. The pathological mechanisms underlying Alzheimer&#39;s disease (AD), a common neurodegenerative disease, remain largely unknown. Altered brain laterality has been demonstrated in aging people, but whether or not abnormal lateralization is one of the early signs of AD has not been determined. To investigate this, we recorded bilateral LFPs in 3-5-month-old AD model mice, APP/PS1, together with littermate wild type (WT) controls. The LFPs of the left and right secondary motor cortex (M2), specifically in the gamma band, were more synchronized in APP/PS1 mice than in WT controls, suggesting a declined hemispheric asymmetry of bilateral M2 in this AD mouse model. Notably, the recording and data analysis processes are flexible and easy to carry out, and can also be applied to other brain pathways when conducting experiments that focus on neuronal circuits.

We present in vivo electrophysiological recording of the local field potential (LFP) in bilateral secondary motor cortex (M2) of mice, which can be applied to evaluate hemisphere lateralization. The study revealed altered levels of synchronization between the left and right M2 in APP/PS1 mice compared to WT controls.

This article demonstrates complete, detailed procedures for both in vivo bilateral recording and analysis of local field potential (LFP) in the cortical ...