This work was supported by grants from the National Natural Science Foundation of China (31871170, 32170950, and 31970915), the Natural Science Foundation of Guangdong Province (2021A1515010804 and 2023A1515010899), the Guangdong Natural Science Foundation for Major Cultivation Project (2018B030336001), and the Guangdong Grant: Key Technologies for Treatment of Brain Disorders(2018B030332001).

All the mice were obtained commercially and maintained in a 12 h light/12 h dark cycle (light on at 08:00 A.M. local time) at a room temperature of 22-25 &#176;C and a relative humidity of 50%-60%. The mice had access to a continuous supply of food and water. All the experiments were carried out in accordance with the Guidelines for Care and Use of Laboratory Animals of South China Normal University and approved by the Institutional Animal Ethics Committee. Male C57BL/6J mice aged 3-5 months old were used for the experiments.
1. Micro-drive system assembly
<ol>
	<li>Connect two computer-designed boards using two stulls and a screw that holds the movable micro-drive and attach the connector to one board (Figure 1A, Bi-iii). Drive the micro-drive by twisting a screw (0.5 mm/circle).</li>
	<li>Ensure the micro-drive can carry two sets of eight guide tubes (~3 cm long, ~50 &#181;m internal diameter, ~125 &#181;m external diameter) for each side of the MC region, and then cut it to the same length (at least 15 mm; Figure 1Biv, v).</li>
	<li>Cut 16 Ni-chrome wires (~5 cm long) with a 35 &#181;m diameter, and then load them successively into the guide tubes, followed by applying the glue to fix them (Figure 1Bi, vi, vii).</li>
	<li>Strip the wire insulation, successively twine each exposed wire to each pin from the connector following the channel map, as well as the reference and ground electrodes, and then slowly coat conducting paint onto each pin (Figure 1Bviii-x).</li>
	<li>Cover the pins using epoxy resin (Figure 1Axi, xii), and then perform gold plating via an impedance tester to reduce the impedance of the electrode tips to ~350 kOhm (Figure 1Bxiii, xiv). Set the parameters of the impedance tester as follows: &#8722;10.08 &#181;A direct current for 1 s with gold plating solution, including 5 mM PtCl4.</li>
	<li>Finally, move the micro-drive to the top by twisting a screw. Check the overall size of the micro-drive system modified as shown in Figure 1A (approximately 15 mm long, 10 mm width, 20 mm height, ~1 g weight). Check the detailed specifications of the computer-designed board and movable component in Figure 1Ai, ii.</li>
</ol>
2. Electrode array implantation
<ol>
	<li>Sterilize the surgery kits, wear sterile gloves and put on a doctor&#39;s sterile white coat before the operation starts.</li>
	<li>To manage the pain, use subcutaneous (s.c.) injection of meloxicam&#160;injectable&#160;(5 mg/kg) for the mouse in an induction chamber. Then anesthetize the mouse by an intraperitoneal (i.p.) injection of pentobarbital (80 mg/kg) in an induction chamber18,19. Apply a supplemental dose of pentobarbital (20 mg/kg/h) if the toe pinch reflex is still present.</li>
	<li>Fix the mouse in a stereotaxic apparatus and maintain its rectal temperature at 37 &#176;C by using a temperature controller.</li>
	<li>Apply tetracycline eye ointment to both eyes of the mouse and change sterile gloves&#160;again before surgery.</li>
	<li>Shave the mouse&#39;s fur and disinfect the surgical site with three alternating rounds of betadine scrub and alcohol using a sterile cotton-tipped applicator in concentric circles starting at the center and moving outward&#160;(Figure 2i, ii). Make a small midline incision (~15 mm) to expose its skull. Immediately, apply the 1% lidocaine locally to the neck muscles for pain relief. Then, remove the residual tissue using scissors, and clean the skull using saline-coated cotton buds&#160;(Figure 2iii).</li>
	<li>Using a glass microelectrode filled with ink, mark the desired locations of the bilateral MC for implantation (Figure 2iv, v). Based on a previous study20, the locations of the bilateral MC are as follows: 0.74 mm anterior to the bregma, and 1.25 mm lateral to the midline.</li>
	<li>Implant four stainless steel screws (0.8 mm diameter) to protect the micro-drive system, and then link all the screws together with the reference and ground electrodes, followed by covering with mixed dental cement to form walls (Figure 2vi-xi).</li>
	<li>Carefully drill two small holes (~1.5 mm2) with a skull drill on both the left and right sides of the coordinated skull in the MC regions (Figure 2xii). Use the stereotaxic coordinates of the bilateral MC: 0.74 mm anterior to the bregma, 1.25 mm lateral to the midline, and 0.5 mm ventral to the dura.</li>
	<li>Remove the dura mater from the holes carefully with fine forceps (Figure 2xiii).</li>
	<li>Insert the micro-drive system into the center of the holes using a micromanipulator at 10 &#181;m/s (Figure 2xiv-xvii).</li>
	<li>Fill the petroleum jelly into the dental cement walls after finishing the insertion of the micro-drive system (Figure 2xviii).</li>
	<li>Join the bottom plate of the micro-drive system and the dental cement walls with the mixed dental cement (Figure 2xix)</li>
	<li>Wash the incision with saline followed by local treatment with a gel containing lincomycin hydrochloride and lidocaine hydrochloride to relieve post-surgical pain.</li>
	<li>Wind the conductive copper foil tape around the implanted micro-drive system (Figure 2xx).</li>
	<li>Move the mouse into a cage kept at 31-33 &#176;C and monitor the mouse for recovery from the anesthesia.</li>
	<li>Allow the mice to recover for 1 week with separate feeding. Check and treat the incision with 3 days of continuous application of a gel containing lincomycin hydrochloride and lidocaine hydrochloride.</li>
</ol>
3. Multichannel recording in the bilateral MC in free-moving mice
<ol>
	<li>Hold the head of an awake mouse lightly and carefully. Move down the electrode arrays (~0.1 mm depth) by twisting the screw on the movable part of the micro-drive system (Figure 1Aii) at least 1 day in advance.</li>
	<li>Hold the head of the awake mouse lightly and carefully. Link the center of the headstage and a helium balloon (filled with approximately 0.02 L of helium) with a thread to offset the weight of the headstage and the micro-drive system (Figure 3A, B).</li>
	<li>Capture raw signals using the recording electrodes and multichannel systems by sampling at 30 kHz in the recording software, and then digitize using a digital-analog (DA) converter from the multichannel systems.</li>
	<li>Extract the LFP signals from the raw data by resampling at 10 kHz in the recording software, and then use a notch filter from the recording software to remove the 50 Hz line noise.</li>
	<li>Record raw data in a stable state from a free-moving mouse for at least 60 s. After finishing the recording, slowly remove the connection between the headstage and the micro-drive system and return the mouse back to its home cage.</li>
	<li>Store the recorded data in the computer and analyze it offline (Figure 4 and Figure 5).</li>
	<li>After finishing the experiment, perform euthanasia as per the institute&#39;s guidelines and then confirm the locations of the electrodes by using the power supply at 3 V output to perform a 1 min electrolytic lesion, followed by performing histological analysis. Cut the mouse&#39;s brain into 30 &#181;m slices using a freezing microtome, collect the MC sections, and then capture the images with a microscope (Figure 3C, D).</li>
</ol>
4. Spike sorting and analysis
<ol>
	<li>Click on File &#62; Open &#62; Nev files in the spike sorting software to open the spike data sampled at 30 kHz (Figure 4Ai).</li>
	<li>Click on Info to select the unsorted channel, and then select Sort &#62; Change Sort Method &#62; Use K-Means. Press the button Valley-Seeking Sort &#62; K-Means Sorting to obtain the sorted units (Figure 4Aii, iii).</li>
	<li>Click on File &#62; Save as, save the sorted spike data with a .nev filename extension, and select File &#62; Export Per-Waveform Data to export the PCA results with a .txt filename extension (Figure 4Aiv).</li>
	<li>Click on File &#62; Import Data &#62; Blackrock File in the software for the neurophysiological data analysis to open the sorted spike file (Figure 4Bi).</li>
	<li>Click on Analysis &#62; Autocorrelograms to obtain the autocorrelogram for the selected unit, and then set the parameters as follows: the X Minimum value at &#8722;0.05 s, the X Maximum value at 0.05 s, and the Bin value at 0.001 (Figure 4Bii, iii).</li>
	<li>Load the sorted spike data, click on Analysis &#62; Interspike Interval Histograms to obtain the inter-spike interval histogram, and then set the parameters as follows: the Min. interval value at 0 s, the Max. interval value at 0.1 s, and the Bin value at 0.001 (Figure 4Biv, v).</li>
	<li>Click on Analysis &#62; Crosscorrelograms to obtain the cross-correlogram between two sorted unit events, and then set the reference events and parameters as follows: the X Minimum value at &#8722;0.1 s, the X Maximum value at 0.1 s, and the Bin value at 0.001 (Figure 4Bvi, vii).</li>
	<li>Click on Results &#62; Numerical Results to save the results of the autocorrelogram, inter-spike interval histogram, and cross-correlogram with .xls filename extensions (Figure 4Bviii, ix). Analyze the data, and draw the graph.</li>
</ol>
5. LFP analysis
<ol>
	<li>Click on File Import Data &#62; Blackrock File in the software for the neurophysiological data analysis to open the continuous signal data sampled at 10 kHz (Figure 5Ai).</li>
	<li>Click on Analysis &#62; Spectrum for Continuous to analyze the power spectrum for the LFP from the selected channel. Set the parameters as follows: the Number of Frequency Values at 8,192, the Multiple Tapers value at 3-5, the Normalization of the percentage of the total power spectral density (PSD), and the Frequency range from 1 Hz to 100 Hz (Figure 5Aii, iii).</li>
	<li>Click on Analysis &#62; Coherence for Continuous to analyze the coherence for two LFPs from the left and right sides of the MC. Set the reference channel and parameters as follows: Calculate at Coherence Values, the Number of Frequency Values at 8,192, the Multiple Tapers value at 3-5, and the frequency range from 1 Hz to 100 Hz (Figure 5Aiv, v).</li>
	<li>Click on Analysis &#62; Corr. with Cont. Variables to analyze the correlation between two LFPs from the left and right sides of the MC. Set the reference channel (LFP data) and parameters as follows: the X Minimum value at &#8722;0.1 s, the X Maximum value at 0.1 s, and the Bin value at 0.001 (Figure 5Avi, vii).</li>
	<li>Click on Results &#62; Numerical Results to save the results of the PSD, coherence, and correlation with an .xls filename extension (Figure 5Aviii, ix).</li>
	<li>Select the channel for which the representative traces need to be extracted for each frequency band, click on Edit &#62; Digital Filtering of Continuous Variables to obtain each frequency band, and then set the parameters as follows: the Filter Freq. Response as Bandpass, the Filter Implementation at infinite impulse response (IIR) Butterworth, and the Filter Order value at 2. Finally, set the frequency range of interest (Figure 5Bi-iv). 
	NOTE: The frequency ranges used here were as follows: delta (&#948;, 1-4 Hz), theta (&#952;, 5-12 Hz), beta (&#946;, 13-30 Hz), low gamma (low &#947;, 30-70 Hz), and high gamma (high &#947;, 70-100 Hz) oscillations.</li>
	<li>Analyze the data and draw the graph.</li>
</ol>
6. Correlations between the spike and LFP
<ol>
	<li>Click on File &#62; Import Data &#62; Blackrock File in the software for the neurophysiological data analysisto open the continuous signal data and spike data.</li>
	<li>Click on Analysis &#62; Coherence Analysis to analyze the coherence between the spikes and LFP from the selected channel. Set the reference variable (spike timing) and parameters as follows: Calculate at Coherence Values, the Number of Frequency Values at 512, the Multiple Tapers value at 3-5, and the frequency range from 1 Hz to 100 Hz (Figure 5Ci, ii).</li>
	<li>Click on Results &#62; Numerical Results to save the result of the spike field coherence with an .xls filename extension (Figure 5Ciii, iv).</li>
	<li>Analyze the data and draw the graph.</li>
</ol>

Extracellular Electrophysiological Recording in the Motor Cortex of Mice

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The authors have nothing to disclose.

Multichannel recording in free-moving mice has been deemed to be a useful technology in neuroscience studies, but it is still quite challenging for beginners to record and analyze the signals. In the present study, we provide simplified guidelines for making micro-drive systems and performing electrode implantation, as well as simplified procedures for capturing and analyzing the electrical signals via spike sorting software and software for neurophysiological data analysis.
Given tha...

The local field potential (LFP), an important component of extracellular signals, reflects the synaptic activity of large populations of neurons, which form the neural code for multiple behaviors1. Spikes generated by neuronal activity are considered to contribute to the LFP and are important for neural coding2. Alterations in spikes and LFPs have been proven to mediate several brain diseases, such as Alzheimer&#39;s disease, as well as emotions such as fear, etc.3,4. It is worth noting that many studies have highlighted that spike activity significantly differs between awake and anesthetized states in animals5. Although recordings in anesthetized animals offer an opportunity to assess LFPs with minimal artifacts in highly defined cortical synchronization states, the results differ to some extent from what can be found in awake subjects6,7,8. Thus, it is more meaningful to detect neural activity over long time scales and large spatial scales in various diseases in an awake brain state using electrodes implanted in the brain. This manuscript provides information for beginners on how to make the micro-drive system and set the parameters using common software for computing the spike and LFP signals in a fast and straightforward way in order to get the recording and analysis started.
Although the non-invasive recording of brain functions, such as by using electroencephalograms (EEGs) and event-related potentials (ERPs) recorded from the scalp, has been used extensively in human and rodent studies, EEG and ERP data have low spatial and temporal properties and, thus, cannot detect the precise signals produced by nearby dendritic synaptic activity within a specific brain area1. Currently, by taking advantage of multichannel recording in conscious animals, neural activity in the deeper layers of the brain can be recorded chronically and progressively by implanting a micro-drive system into the brains of primates or rodents during multiple behavioral tests1,2,3,4,5,6,7,8,9. Briefly, researchers can construct a micro-drive system that can be used for the independent positioning of the electrodes or tetrodes to target different parts of the brain10,11. For example, Chang et al. described techniques to record spikes and LFPs in mice by assembling a light and compact micro-drive12. In addition, micro-machined silicon probes with custom-made accessory components are commercially available for recording multiple single neurons and LFPs in rodents during behavioral tasks13. Although various designs have been used for assembling micro-drive systems, these still have limited success in terms of the complexity and weight of the whole micro-drive system. For example, Lansink et al. showed a multichannel micro-drive system with a complex structure for recording from a single brain region14. Sato et al. reported a multichannel micro-drive system displaying an automatic hydraulic positioning function15. The main disadvantages of these micro-drive systems are that they are too heavy for mice to move freely and are difficult to assemble for beginners. Although multichannel extracellular recording has been shown to be a suitable and efficient technology for measuring neural activity during behavioral tests, it is not easy for beginners to record and analyze the signals acquired by the complex micro-drive system. Given that it is difficult to get the entire operation process of the multichannel extracellular recording and data analysis started in freely moving mice16,17, this present article presents simplified guidelines to introduce the detailed process of making the micro-drive system using commonly available components and settings; the parameters in the common software for computing the spike and LFP signals in a fast and straightforward way are also provided. Additionally, in this protocol, the mouse can move freely due to the use of a helium balloon, which contributes to offsetting the weight of headstage and micro-drive system. Generally, in the present study, we describe how to easily build a micro-drive system and optimize the processes of recording and data analysis.

<table><tbody><tr><td>2.54 mm pin header</td><td>YOUXIN Electronic Co., Ltd.</td><td>1 x 5</td><td>Applying for the movable micro-drive which can slide on its stulls.</td></tr><tr><td>Adobe Illustrator CC 2017</td><td>Adobe</td><td>N/A</td><td>To optimize images from GraphPad.</td></tr><tr><td>BlackRock Microsystems</td><td>Blackrock Neurotech</td><td>Cerebus</td><td>This systems includes headsatge, DA convert, amplifier and computer.</td></tr><tr><td>Brass nut</td><td>Dongguan Gaosi Technology Co., Ltd.</td><td>M0.8 brass nut</td><td>The nut fixes the position of screw.</td></tr><tr><td>Brass screw</td><td>Dongguan Gaosi Technology Co., Ltd.</td><td>M0.8 x 11 mm brass screw</td><td>A screw that hold the movable micro-drive.</td></tr><tr><td>C57BL/6J</td><td>Guangdong Zhiyuan Biomedical Technology Co., LTD.</td><td>N/A</td><td>12 weeks of age.</td></tr><tr><td>Centrifuge tube</td><td>Biosharp</td><td>15 mL; BS-150-M</td><td>To store mice brain with sucrose sulutions.</td></tr><tr><td>Conducting paint</td><td>Structure Probe, Inc.</td><td>7440-22-4</td><td>To improve the lead-connecting quality between connector pins and Ni-wires.</td></tr><tr><td>Conductive copper foil tape</td><td>3M</td><td>1181</td><td>To reduce interferenc.</td></tr><tr><td>Connector</td><td>YOUXIN Electronic Co., Ltd.</td><td>2 x 10P</td><td>To connect the headtage to micro-drive system.</td></tr><tr><td>DC Power supply</td><td>Maisheng</td><td>MS-305D</td><td>A power device for&amp;nbsp; electrolytic lesion.</td></tr><tr><td>Dental cement</td><td>Shanghai New Century Dental Materials Co., Ltd.</td><td>N/A</td><td>To fix the electrode arrays on mouse&#039;s skull after finishing the implantation.</td></tr><tr><td>Digital analog converter</td><td>Blackrock</td><td>128-Channel</td><td>A device that converts digital data into analog signals.</td></tr><tr><td>Epoxy resin</td><td>Alteco</td><td>N/A</td><td>To cover pins.</td></tr><tr><td>Excel</td><td>Microsoft</td><td>N/A</td><td>To summarize data after analysis.</td></tr><tr><td>Eye scissors</td><td>JiangXi YuYuan Medical Equipment Co.,Ltd.</td><td>N/A</td><td>For surgery or cutting the Ni-chrome wire.</td></tr><tr><td>Fine forceps</td><td>JiangXi YuYuan Medical Equipment Co.,Ltd.</td><td>N/A</td><td>For surgery.</td></tr><tr><td>Forceps</td><td>JiangXi YuYuan Medical Equipment Co.,Ltd.</td><td>N/A</td><td>For surgery or assembling the mirco-drive system.</td></tr><tr><td>Freezing microtome</td><td>Leica</td><td>CM3050 S</td><td>&amp;nbsp;Cut the mouse&amp;rsquo;s brain into slices</td></tr><tr><td>Fused silica capillary tubing</td><td>Zhengzhou INNOSEP Scientific Co., Ltd.</td><td>TSP050125</td><td>To&amp;nbsp; serve as the guide tubes for Ni-chrome wires.</td></tr><tr><td>Glass microelectrode</td><td>Sutter Instrument Company</td><td>BF100-50-10</td><td>To mark the desired locations for implantation using the filled ink.</td></tr><tr><td>GraphPad Prism 7</td><td>GraphPad Software</td><td>N/A</td><td>To analyze and visualize the results.</td></tr><tr><td>Guide-tube</td><td>Polymicro technologies</td><td>1068150020</td><td>To load Ni-chrome wires.</td></tr><tr><td>Headstage</td><td>Blackrock</td><td>N/A</td><td>A tool of transmitting signals.</td></tr><tr><td>Helium balloon</td><td>Yili Festive products Co., Ltd.</td><td>24 inch</td><td>To offset the weight of headstage and micro-drive system.</td></tr><tr><td>Ink</td><td>Sailor Pen Co.,LTD.</td><td>13-2001</td><td>To mark the desired locations for implantation.</td></tr><tr><td>Iodine tincture</td><td>Guangdong Hengjian Pharmaceutical Co., Ltd.</td><td>N/A</td><td>To disinfect mouse&#039;s scalp.</td></tr><tr><td>Lincomycin in Hydrochloride and Lidocaine&amp;nbsp; hydrochloride gel</td><td>Hubei kangzheng pharmaceutical co., ltd.</td><td>10g</td><td>A drug used to reduce inflammation.</td></tr><tr><td>Meloxicam</td><td>Vicki Biotechnology Co., Ltd.</td><td>71125-38-7</td><td>To reduce postoperative pain in mice.</td></tr><tr><td>Micromanipulators</td><td>Scientifica</td><td>Scientifica IVM Triple</td><td>For electrode arrays implantation.</td></tr><tr><td>Microscope&amp;nbsp;</td><td>Nikon</td><td>ECLIPSE Ni-E</td><td>&amp;nbsp;Capture the images of brain sections</td></tr><tr><td>nanoZ impedance tester</td><td>Plexon</td><td>nanoZ</td><td>To measure impedance or performing electrode impedance spectroscopy (EIS) for multichannel microelectrode arrays.</td></tr><tr><td>NeuroExplorer</td><td>Plexon</td><td>NeuroExplorer</td><td>A tool for analyzing the electrophysiological data.</td></tr><tr><td>NeuroExplorer&amp;nbsp;</td><td>Plexon, USA</td><td>N/A</td><td>A software.</td></tr><tr><td>Ni-chrome wire</td><td>California Fine Wire Co.</td><td>M472490</td><td>35 &amp;mu;m Ni-chrome wire.</td></tr><tr><td>Offline Sorter</td><td>Plexon</td><td>Offline Sorter</td><td>A tool for sorting the recorded multi-units.</td></tr><tr><td>PCB board</td><td>Hangzhou Jiepei Information Technology Co., Ltd.</td><td>N/A</td><td>Computer designed board.</td></tr><tr><td>Pentobarbital</td><td>Sigma</td><td>P3761</td><td>To anesthetize mice.</td></tr><tr><td>Pentobarbital sodium</td><td>Sigma</td><td>57-33-0</td><td>To anesthetize the mouse.</td></tr><tr><td>Peristaltic pump</td><td>Longer</td><td>BT100-1F</td><td>A device used for perfusion</td></tr><tr><td>Polyformaldehyde&amp;nbsp;</td><td>Sangon Biotech</td><td>A500684-0500</td><td>The main component of fixative solution for fixation of mouse brains&amp;nbsp;</td></tr><tr><td>PtCl&lt;sub&gt;4&lt;/sub&gt;</td><td>Tianjin Jinbolan Fine Chemical Co., Ltd.</td><td>13454-96-1</td><td>Preparation for gold plating liquid.</td></tr><tr><td>Saline</td><td>Guangdong Hengjian Pharmaceutical Co., Ltd.</td><td>N/A</td><td>To clean the mouse&#039;s skull.</td></tr><tr><td>Silver wire</td><td>Suzhou Xinye Electronics Co., Ltd.</td><td>2 mm diameter</td><td>Applying for ground and reference electrodes.</td></tr><tr><td>Skull drill</td><td>RWD Life Science</td><td>78001</td><td>To drill carefully two small holes on mouse&#039;s skull.</td></tr><tr><td>Stainless steel screws</td><td>YOUXIN Electronic Co., Ltd.</td><td>M0.8 x 2</td><td>To protect the micro-drive system and link the ground and reference electrodes.</td></tr><tr><td>Stereotaxic apparatus</td><td>RWD Life Science</td><td>68513</td><td>To perform the stereotaxic coordinates of bilateral motor cortex.</td></tr><tr><td>Sucrose</td><td>Damao</td><td>57-50-1</td><td>To dehydrate the mouse brains&amp;nbsp; after perfusion.</td></tr><tr><td>Super glue</td><td>Henkel AG &amp;amp; Co.</td><td>PSK5C</td><td>To fix the guide tube and Ni-chrome wire.</td></tr><tr><td>Temperature controller</td><td>Harvard Apparatus</td><td>TCAT-2</td><td>To maintain mouse&#039;s rectal temperature at 37&amp;deg;C</td></tr><tr><td>Tetracycline eye ointment</td><td>Guangdong Hengjian Pharmaceutical Co., Ltd.</td><td>N/A</td><td>To protect the mouse&#039;s eyes during surgery.</td></tr><tr><td>Thread</td><td>Rapala</td><td>N/A</td><td>To link ballon and headstage.</td></tr><tr><td>Vaseline</td><td>Unilever plc</td><td>N/A</td><td>To cover the gap between electrode arrays and mouse&#039;s skull.</td></tr></tbody></table>

multichannel extracellular recording in freely moving mice

The protocol aims to uncover the properties of neuronal firing and network local field potentials (LFPs) in behaving mice carrying out specific tasks by correlating the electrophysiological signals with spontaneous and/or specific behavior. This technique represents a valuable tool in studying the neuronal network activity underlying these behaviors. The article provides a detailed and complete procedure for electrode implantation and consequent extracellular recording in free-moving conscious mice. The study includes a detailed method for implanting the microelectrode arrays, capturing the LFP and neuronal spiking signals in the motor cortex (MC) using a multichannel system, and the subsequent offline data analysis. The advantage of multichannel recording in conscious animals is that a greater number of spiking neurons and neuronal subtypes can be obtained and compared, which allows the evaluation of the relationship between a specific behavior and the associated electrophysiological signals. Notably, the multichannel extracellular recording technique and the data analysis procedure described in the present study can be applied to other brain areas when conducting experiments in behaving mice.

A high-pass (250 Hz) filter was applied to extract the multi-unit spikes from the raw signals (Figure 6A). Further, the recorded units from the MC of a normal mouse sorted by PCA were verified (Figure 7A-D), and the valley width and waveform duration of the units in the MC of the mouse were recorded. The results showed that both the valley width and waveform duration of the MC putative pyramidal neurons (Pyn) in mice are higher ...

Watch this Scientific Journal Video about Advancements in Multichannel Extracellular Recording for Studying Neuronal Activity in Freely Moving Mice at JoVE.com

Author Spotlight: Advancements in Multichannel Extracellular Recording for Studying Neuronal Activity in Freely Moving 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

The protocol aims to uncover the properties of neuronal firing and network local field potentials (LFPs) in behaving mice carrying out specific tasks by ...

multichannel-extracellular-recording-in-freely-moving-mice

Research

JoVE Journal

Neuroscience

2.6K Views.  South China Normal University. We streven ernaar om de eigenschappen van neuronaal vuren bloot te leggen en lokale veldpotentialen te netwerken in zich gedragende muizen die specifieke taken uitvoeren door het elektrofysiologische signaal te correleren met gedrag. Meerkanaals extracellulaire opname door het micro-drive-systeem is een geschikte en efficiënte technologie gebleken voor neurale activiteit tijdens gedragstests. Meerkanaals opname bij vrij bewegende muizen wordt beschouwd als een nuttige technologie in neurowet...

Video: Auteur in de schijnwerpers: vooruitgang in meerkanaals extracellulaire opname voor het bestuderen van neuronale activiteit bij vrij bewegende muizen 

Flat-floored Air-lifted Platform: A New Method for Combining Behavior with Microscopy or Electrophysiology on Awake Freely Moving Rodents

It is widely acknowledged that the use of general anesthetics can undermine the relevance of electrophysiological or microscopical data obtained from a living animal&#8217;s brain. Moreover, the lengthy recovery from anesthesia limits the frequency of repeated recording/imaging episodes in longitudinal studies. Hence, new methods that would allow stable recordings from non-anesthetized behaving mice are expected to advance the fields of cellular and cognitive neurosciences. Existing solutions range from mere physical restraint to more sophisticated approaches, such as linear and spherical treadmills used in combination with computer-generated virtual reality. Here, a novel method is described where a head-fixed mouse can move around an air-lifted mobile homecage and explore its environment under stress-free conditions. This method allows researchers to perform behavioral tests (e.g., learning, habituation or novel object recognition) simultaneously with two-photon microscopic imaging and/or patch-clamp recordings, all combined in a single experiment. This video-article describes the use of the awake animal head fixation device (mobile homecage), demonstrates the procedures of animal habituation, and exemplifies a number of possible applications of the method.

This method creates a tangible, familiar environment for the mouse to navigate and explore during microscopic imaging or single-cell electrophysiological recordings, which require firm fixation of the animal&#8217;s head.

It is widely acknowledged that the use of general anesthetics can undermine the relevance of electrophysiological or microscopical data obtained from a ...

Behavior

High-density EEG Recordings of the Freely Moving Mice using Polyimide-based Microelectrode

Electroencephalogram (EEG) indicates the averaged electrical activity of the neuronal populations on a large-scale level. It is widely utilized as a noninvasive brain monitoring tool in cognitive neuroscience as well as a diagnostic tool for epilepsy and sleep disorders in neurology. However, the underlying mechanism of EEG rhythm generation is still under the veil. Recently introduced polyimide-based microelectrode (PBM-array) for high resolution mouse EEG1 is one of the trials to answer the neurophysiological questions on EEG signals based on a rich genetic resource that the mouse model contains for the analysis of complex EEG generation process. This application of nanofabricated PBM-array to mouse skull is an efficient tool for collecting large-scale brain activity of transgenic mice and accommodates to identify the neural correlates to certain EEG rhythms in conjunction with behavior. However its ultra-thin thickness and bifurcated structure cause a trouble in handling and implantation of PBM-array. In the presented video, the preparation and surgery steps for the implantation of PBM-array on a mouse skull are described step by step. Handling and surgery tips to help researchers succeed in implantation are also provided.

In this article, we described the surgery procedure and handling tips for implantation of ultra-thin polyimide-based microelectrode array (PBM-array) on the mouse skull for acquisition of high-density encephalography (EEG) in a mouse model.

Electroencephalogram (EEG) indicates the averaged electrical activity of the neuronal populations on a large-scale level. It is widely utilized as a ...

Simultaneous Video-EEG-ECG Monitoring to Identify Neurocardiac Dysfunction in Mouse Models of Epilepsy

In epilepsy, seizures can evoke cardiac rhythm disturbances such as heart rate changes, conduction blocks, asystoles, and arrhythmias, which can potentially increase risk of sudden unexpected death in epilepsy (SUDEP). Electroencephalography (EEG) and electrocardiography (ECG) are widely used clinical diagnostic tools to monitor for abnormal brain and cardiac rhythms in patients. Here, a technique to simultaneously record video, EEG, and ECG in mice to measure behavior, brain, and cardiac activities, respectively, is described. The technique described herein utilizes a tethered (i.e., wired) recording configuration in which the implanted electrode on the head of the mouse is hard-wired to the recording equipment. Compared to wireless telemetry recording systems, the tethered arrangement possesses several technical advantages such as a greater possible number of channels for recording EEG or other biopotentials; lower electrode costs; and greater frequency bandwidth (i.e., sampling rate) of recordings. The basics of this technique can also be easily modified to accommodate recording other biosignals, such as electromyography (EMG) or plethysmography for assessment of muscle and respiratory activity, respectively. In addition to describing how to perform the EEG-ECG recordings, we also detail methods to quantify the resulting data for seizures, EEG spectral power, cardiac function, and heart rate variability, which we demonstrate in an example experiment using a mouse with epilepsy due to Kcna1 gene deletion. Video-EEG-ECG monitoring in mouse models of epilepsy or other neurological disease provides a powerful tool to identify dysfunction at the level of the brain, heart, or brain-heart interactions.

Here, we present a protocol to record brain and heart bio signals in mice using simultaneous video, electroencephalography (EEG), and electrocardiography (ECG). We also describe methods to analyze the resulting EEG-ECG recordings for seizures, EEG spectral power, cardiac function, and heart rate variability.

In epilepsy, seizures can evoke cardiac rhythm disturbances such as heart rate changes, conduction blocks, asystoles, and arrhythmias, which can ...

Genetics

Juxtacellular Monitoring and Localization of Single Neurons within Sub-cortical Brain Structures of Alert, Head-restrained Rats

There are a variety of techniques to monitor extracellular activity of single neuronal units. However, monitoring this activity from deep brain structures in behaving animals remains a technical challenge, especially if the structures must be targeted stereotaxically. This protocol describes convenient surgical and electrophysiological techniques that maintain the animal&#8217;s head in the stereotaxic plane and unambiguously isolate the spiking activity of single neurons. The protocol combines head restraint of alert rodents, juxtacellular monitoring with micropipette electrodes, and iontophoretic dye injection to identify the neuron location in post-hoc histology. While each of these techniques is in itself well-established, the protocol focuses on the specifics of their combined use in a single experiment. These neurophysiological and neuroanatomical techniques are combined with behavioral monitoring. In the present example, the combined techniques are used to determine how self-generated vibrissa movements are encoded in the activity of neurons within the somatosensory thalamus. More generally, it is straightforward to adapt this protocol to monitor neuronal activity in conjunction with a variety of behavioral tasks in rats, mice, and other animals. Critically, the combination of these methods allows the experimenter to directly relate anatomically-identified neurophysiological signals to behavior.

This protocol describes the design and surgical implantation of a head-restraining mechanism to monitor neuronal activity in sub-cortical brain structures in alert rats. It delineates procedures to isolate single neurons in the juxtacellular configuration and to efficiently identify their anatomical locations.

There are a variety of techniques to monitor extracellular activity of single neuronal units. However, monitoring this activity from deep brain structures ...

Extracellular Recording of Neuronal Activity Combined with Microiontophoretic Application of Neuroactive Substances in Awake Mice

Differences in the activity of neurotransmitters and neuromodulators, and consequently different neural responses, can be found between anesthetized and awake animals. Therefore, methods allowing the manipulation of synaptic systems in awake animals are required in order to determine the contribution of synaptic inputs to neuronal processing unaffected by anesthetics. Here, we present methodology for the construction of electrodes to simultaneously record extracellular neural activity and release multiple neuroactive substances at the vicinity of the recording sites in awake mice. By combining these procedures, we performed microiontophoretic injections of gabazine to selectively block GABAA receptors in neurons of the inferior colliculus of head-restrained mice. Gabazine successfully modified neural response properties such as the frequency response area and stimulus-specific adaptation. Thus, we demonstrate that our methods are suitable for recording single-unit activity and for dissecting the role of specific neurotransmitter receptors in auditory processing.
The main limitation of the described procedure is the relatively short recording time (~3 hr), which is determined by the level of habituation of the animal to the recording sessions. On the other hand, multiple recording sessions can be performed in the same animal. The advantage of this technique over other experimental procedures used to manipulate the level of neurotransmission or neuromodulation (such as systemic injections or the use of optogenetic models), is that the drug effect is confined to the local synaptic inputs to the target neuron. In addition, the custom-manufacture of electrodes allows adjustment of specific parameters according to the neural structure and type of neuron of interest (such as the tip resistance for improving the signal-to-noise ratio of the recordings).

We present methods for the construction of electrodes to simultaneously record extracellular neural activity and release multiple neuroactive substances at the vicinity of the recording sites in awake mice. This technique allows the detailed analysis of putative local synaptic inputs to the neuron of interest.

Differences in the activity of neurotransmitters and neuromodulators, and consequently different neural responses, can be found between anesthetized and ...

Syringe-injectable Mesh Electronics for Stable Chronic Rodent Electrophysiology

Implantable brain electrophysiology probes are valuable tools in neuroscience due to their ability to record neural activity with high spatiotemporal resolution from shallow and deep brain regions. Their use has been hindered, however, by mechanical and structural mismatches between the probes and brain tissue that commonly lead to micromotion and gliosis with resulting signal instability in chronic recording experiments. In contrast, following the implantation of ultraflexible mesh electronics via syringe injection, the mesh probes form a seamless, gliosis-free interface with the surrounding brain tissue that enables stable tracking of individual neurons on at least a year timescale. This protocol details the key steps in a typical mouse neural recording experiment using syringe-injectable mesh electronics, including the fabrication of mesh electronics in a standard photolithography-based process possible at many universities, loading mesh electronics into standard capillary needles, stereotaxic injection in vivo, connection of the mesh input/output to standard instrumentation interfaces, restrained or freely moving recording sessions, and histological sectioning of brain tissue containing mesh electronics. Representative neural recordings and histology data are presented. Investigators familiar with this protocol will have the knowledge necessary to incorporate mesh electronics into their own experiments and take advantage of the unique opportunities afforded by long-term stable neural interfacing, such as studies of aging processes, brain development, and the pathogenesis of brain disease.

Mesh electronics probes seamlessly integrate and provide stable, long-term, single-neuron level recording within the brain. This protocol uses mesh electronics for in vivo experiments, involving the fabrication of mesh electronics, loading into needles, stereotaxic injection, input/output interfacing, recording experiments, and histology of tissue containing mesh probes.

Implantable brain electrophysiology probes are valuable tools in neuroscience due to their ability to record neural activity with high spatiotemporal ...

Bioengineering

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 ...

Stimulating Mouse Brain with a Low-Cost EEG and Millimeter-Sized Coil

Low-Cost Electroencephalographic Recording System Combined with a Millimeter-Sized Coil to Transcranially Stimulate the Mouse Brain In Vivo

A low-cost electroencephalographic (EEG) recording system is proposed here to drive transcranial magnetic stimulation (TMS) of the mouse brain in vivo, utilizing a millimeter-sized coil. Using conventional screw electrodes combined with a custom-made, flexible, multielectrode array substrate, multi-site recording can be carried out from the mouse brain. In addition, we explain how a millimeter-sized coil is produced using low-cost equipment usually found in laboratories. Practical procedures for fabricating the flexible multielectrode array substrate and the surgical implantation technique for screw electrodes are also presented, which are necessary to produce low-noise EEG signals. Although the methodology is useful for recording from the brain of any small animal, the present report focuses on electrode implementation in an anesthetized mouse skull. Furthermore, this method can be easily extended to an awake small animal that is connected with tethered cables via a common adapter and fixed with a TMS device to the head during recording.The present version of the EEG-TMS system, which can include a maximum of 32 EEG channels (a device with 16 channels is presented as an example with fewer channels) and one TMS channel device, is described. Additionally, typical results obtained by the application of the EEG-TMS system to anesthetized mice are briefly reported.

Author Spotlight: Low-Cost Electroencephalographic Recording System Combined with a Millimeter-Sized Coil to Transcranially Stimulate the Mouse Brain In Vivo  

A low-cost electroencephalographic recording system combined with a millimeter-sized coil is proposed to drive transcranial magnetic stimulation of the mouse brain in vivo. Using conventional screw electrodes with a custom-made, flexible, multielectrode array substrate, multi-site recording can be carried out from the mouse brain in response to transcranial magnetic stimulation.

A low-cost electroencephalographic (EEG) recording system is proposed here to drive transcranial magnetic stimulation (TMS) of the mouse brain in vivo, ...

Injectable Mesh Electronics for Stable Single-Neuron Recordings in a Mouse Brain

Source: Schuhmann Jr., T. G., et al. <a href="https://app.jove.com/v/58003">Syringe-injectable Mesh Electronics for Stable Chronic Rodent Electrophysiology.</a> J. Vis. Exp. (2018).
The video demonstrates the injection of mesh electronics probes into a mouse brain for stable long-term recordings at a single-neuron level. An anesthetized mouse with an exposed skull is secured on a stereotaxic frame, and the probe&#39;s mesh device region is injected into the brain through drilled holes. The probe&#39;s input-output pads are connected to a circuit, and recordings are obtained using a data acquisition system.

1. Stereotaxic Injection of Mesh Electronics into Live Mouse Brain
NOTE: Mice were anesthetized by intraperitoneal injection with a mixture of 75 mg/kg ...

JoVE Encyclopedia of Experiments

Neurophysiology

Stimulation and Modulation Techniques

Investigating Auditory Neuronal Responses in an Awake Mouse in the Presence of an Inhibitory Neurotransmitter Blocker

Source: Ayala, Y. A., et al. <a href="https://app.jove.com/v/53914">Extracellular Recording of Neuronal Activity Combined with Microiontophoretic Application of Neuroactive Substances in Awake Mice.</a> J. Vis. Exp. (2016).
This video demonstrates the study of neuronal activity in a specific region of the mouse brain that processes auditory stimuli. The technique involves applying an inhibitory neurotransmission blocker and comparing neuronal responses to auditory stimuli before and after the drug is applied to the localized brain region.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
1. Drugs ...

Multichannel Extracellular Recording in Freely Moving Mice

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