This work was supported by&#160;the&#160;Royal Melbourne Hospital Neuroscience Foundation (A2087).

This study was approved by the Florey Animal Ethics Committee (The University of Melbourne, No. 22-025UM) in accordance with the Australian code for the care and use of animals for scientific purposes. C57BL/6 male mice (8 weeks), obtained from the Animal Resources Centre (Australia), were used for the present study.
1. Headstage design and fabrication
NOTE: The headstage PCB board is a compact 14 mm x 12 mm four-layer board designed to be placed directly on the animal&#39;s head. It utilizes a commercial amplifier chip (see Table of Materials), and all design and Gerber files are available online (GitHub link:&#160;https://github.com/dechuansun/Intan-headstage/tree/main/pcbway).
<ol>
	<li>Provide the following specifications to the manufacturer: Board thickness: 0.6 mm; Minimum tracking/spacing: 4 mils; Minimum hole size: 0.2 mm.</li>
	<li>During the PCB assembly process, follow this order:
	<ol>
		<li>Solder the amplifier chip onto the board using a hot air gun set at 350 &#176;C.</li>
		<li>Solder the passive components.</li>
		<li>Solder the SPI connector and the electrode connector (see Table of Materials).</li>
	</ol>
	</li>
	<li>Inspect the soldering under a microscope for quality assurance. Secure the SPI connector in place using epoxy for added stability.</li>
	<li>Use third-party recording software and a control board (see Table of Materials) for signal acquisition. Refer to the software user guide for detailed instructions.</li>
	<li>The designed headstage supports 8 channels. In the software, enable channels 8, 9, 12, 13, 20, 21, 22, and 23 for recording.</li>
</ol>
2. Electrode fabrication
<ol>
	<li>Cut PFA-coated tungsten wires (see Table of Materials) to specific lengths for different electrode types: prefrontal cortex electrode (12 mm), hippocampus electrode (10 mm), and ground electrode (6 mm).</li>
	<li>Cut the brass tube (see Table of Materials) into 3 mm segments.</li>
	<li>Remove 2 mm of the coating at the end of each wire using a lighter, then securely solder the electrode wire to the brass tube. The brass tube has an inside diameter of 0.45 mm and an outside diameter of 0.60 mm.</li>
	<li>For the ground electrode, solder an M1.2 stainless steel screw (see Table of Materials) to the electrode. Apply phosphoric acid-based flux to the screw to enhance soldering. After soldering, clean the screw using alcohol. 
	&#8203;NOTE: Wear gloves for protection during the soldering process.</li>
</ol>
3. Surgical procedure
<ol>
	<li>Anesthetize the mouse in an anesthesia chamber with 3% isoflurane and 1 L/min oxygen flow.</li>
	<li>Place the anesthetized mouse on a heating pad and secure it in a stereotaxic frame (see Table of Materials).</li>
	<li>Adjust the maintenance rate of isoflurane to 2.5-3% and reduce the oxygen flow to 500 mL/min. Using the toe pinch, verify if the animal is still under deep anesthesia.</li>
	<li>Subcutaneously inject carprofen at 0.5 mg/kg and apply eye ointment for eye protection.</li>
	<li>Shave and sterilize the mouse&#39;s head using povidone-iodine and 80% ethanol.</li>
	<li>Make an 8 mm incision along the midline of the scalp, removing connective tissue in the incision area.</li>
	<li>Apply hydrogen peroxide to clean the surface of the skull, being cautious not to touch the surrounding skin.</li>
	<li>Align the bregma and lambda landmarks to the same level for accurate electrode placement (bregma and lambda are where the sagittal suture intersects the coronal and lambdoid sutures).</li>
	<li>Drill holes for reference/ground electrode, anchor screws (0.9 mm drill burr), and active electrodes (0.3 mm drill burr) at specified coordinates.</li>
	<li>Attach the custom-made electrode (step 2) to the stereotaxic frame arm and ensure it is perpendicular to the brain.</li>
	<li>Implant the electrode in the hippocampal CA1 area (AP - 1.8 mm, ML - 1.3 mm, DV - 1.4 mm). 
	NOTE: AP, anteroposterior; ML, mediolateral; DV, dorsoventral.</li>
	<li>Repeat electrode implantation in the prefrontal cortex (AP - 2.0 mm, ML - 0.3 mm, DV - 1.7 mm).</li>
	<li>Secure electrodes with a commercially available powerful adhesive and dental cement (see Table of Materials).</li>
	<li>Implant two 1.2 mm anchor screws (AP - 1.8 mm, ML -1.6 mm) to prevent movement.</li>
	<li>Position the reference/ground electrode in direct contact with the dura mater, 2 mm posterior and 2 mm unilateral to the lambda landmark.</li>
	<li>Connect the brass tube side of the electrodes to a multi-channel socket connector (see Table of Materials) with the ground electrode in the middle.</li>
	<li>Use 0.8 mm heat shrink tubing on the exterior of the middle pin for isolation.</li>
	<li>Secure the electrodes, anchor screws, and connector with adhesive and dental cement.</li>
</ol>
4. Postoperative care
<ol>
	<li>To alleviate postoperative pain, inject carprofen at a dose of 5-10 mg/kg subcutaneously every 12-24 hours based on an assessment of pain for a period of three days.</li>
	<li>Provide the animal with a one-week recovery period before starting any recording or experimental procedures.</li>
</ol>
5. Recording procedure
<ol>
	<li>Handle the animal for 15 min, twice daily, for three consecutive days.</li>
	<li>Pick up the mice by gently closing the hand around them without applying excessive pressure.</li>
	<li>Place the headstage board on the animal&#39;s head for 30 min once a day for three consecutive days.</li>
	<li>On the recording day, acclimate the animal to the recording room for 30 min.</li>
	<li>Place the animal in a small recording chamber within a Faraday cage to reduce external electrical interference. Attach the custom headstage for recording.</li>
	<li>Open the recording software and select a 2.00 kHz sampling rate. Disable all channels except for 13 and 20 by selecting each channel and pressing the space bar.</li>
	<li>In the hardware bandwidth window, set the lower bandwidth to 2 Hz and the upper bandwidth to 100 Hz.</li>
	<li>In the software filtering window, adjust the low-pass filter to 100 Hz and the high-pass filter to 2 Hz.</li>
	<li>Choose the storage path by clicking on Select File Name, and then click on Record.</li>
	<li>Start each recording session with a 10 min habituation period followed by a 15 min baseline EEG recording.</li>
	<li>After the baseline recording, administer the drug via intraperitoneal injection and continue recording for an additional 30 min without delay. 
	NOTE: See the Results section for the details on the drugs used.</li>
</ol>

LFP Recording in Mouse Brain for Cognitive Research and Drug Analysis

<ol><li>Einevoll, G. T., Kayser, C., Logothetis, N. K., Panzeri, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Modelling+and+analysis+of+local+field+potentials+for+studying+the+function+of+cortical+circuits%5BTitle%5D)+AND+%22Nat+Rev+Neurosci%22%5BJournal%5D)">Modelling and analysis of local field potentials for studying the function of cortical circuits.</a> Nat Rev Neurosci. 14 (11), 770-785 (2013).</li>
<li>Buzsaki, G., Anastassiou, C. A., Koch, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+origin+of+extracellular+fields+and+currents-EEG%2C+ECOG%2C+LFP+and+spikes%5BTitle%5D)+AND+%22Nat+Rev+Neurosci%22%5BJournal%5D)">The origin of extracellular fields and currents-EEG, ECOG, LFP and spikes.</a> Nat Rev Neurosci. 13 (6), 407-420 (2012).</li>
<li>Sigurdsson, T., Stark, K. L., Karayiorgou, M., Gogos, J. A., Gordon, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Impaired+hippocampal-prefrontal+synchrony+in+a+genetic+mouse+model+of+schizophrenia%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Impaired hippocampal-prefrontal synchrony in a genetic mouse model of schizophrenia.</a> Nature. 464 (7289), 763-767 (2010).</li>
<li>Witton, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Disrupted+hippocampal+sharp-wave+ripple-associated+spike+dynamics+in+a+transgenic+mouse+model+of+dementia%5BTitle%5D)+AND+%22J+Physiol%22%5BJournal%5D)">Disrupted hippocampal sharp-wave ripple-associated spike dynamics in a transgenic mouse model of dementia.</a> J Physiol. 594 (16), 4615-4630 (2016).</li>
<li>Englot, D. J., Konrad, P. E., Morgan, V. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Regional+and+global+connectivity+disturbances+in+focal+epilepsy%2C+related+neurocognitive+sequelae%2C+and+potential+mechanistic+underpinnings%5BTitle%5D)+AND+%22Epilepsia%22%5BJournal%5D)">Regional and global connectivity disturbances in focal epilepsy, related neurocognitive sequelae, and potential mechanistic underpinnings.</a> Epilepsia. 57 (10), 1546-1557 (2016).</li>
<li>Pievani, M., De Haan, W., Wu, T., Seeley, W. W., Frisoni, G. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Functional+network+disruption+in+the+degenerative+dementias%5BTitle%5D)+AND+%22Lancet+Neurol%22%5BJournal%5D)">Functional network disruption in the degenerative dementias.</a> Lancet Neurol. 10 (9), 829-843 (2011).</li>
<li>Sigurdsson, T., Duvarci, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Hippocampal-prefrontal+interactions+in+cognition%2C+behavior+and+psychiatric+disease%5BTitle%5D)+AND+%22Front+Syst+Neurosci%22%5BJournal%5D)">Hippocampal-prefrontal interactions in cognition, behavior and psychiatric disease.</a> Front Syst Neurosci. 9, 190(2015).</li>
<li>Sun, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effects+of+antipsychotic+drugs+and+potassium+channel+modulators+on+spectral+properties+of+local+field+potentials+in+mouse+hippocampus+and+pre-frontal+cortex%5BTitle%5D)+AND+%22Neuropharmacology%22%5BJournal%5D)">Effects of antipsychotic drugs and potassium channel modulators on spectral properties of local field potentials in mouse hippocampus and pre-frontal cortex.</a> Neuropharmacology. 191, 108572(2021).</li>
<li>Bokil, H., Andrews, P., Kulkarni, J. E., Mehta, S., Mitra, P. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Chronux%3A+A+platform+for+analyzing+neural+signals%5BTitle%5D)+AND+%22J+Neurosci+Methods%22%5BJournal%5D)">Chronux: A platform for analyzing neural signals.</a> J Neurosci Methods. 192 (1), 146-151 (2010).</li>
<li>Bozkurt, A., Lal, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Low-cost+flexible+printed+circuit+technology+based+microelectrode+array+for+extracellular+stimulation+of+the+invertebrate+locomotory+system%5BTitle%5D)+AND+%22Sens+Actuator+A+Phys%22%5BJournal%5D)">Low-cost flexible printed circuit technology based microelectrode array for extracellular stimulation of the invertebrate locomotory system.</a> Sens Actuator A Phys. 169 (1), 89-97 (2011).</li>
<li>Du, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((High-resolution+mapping+of+in+vivo+gastrointestinal+slow+wave+activity+using+flexible+printed+circuit+board+electrodes%3A+Methodology+and+validation%5BTitle%5D)+AND+%22Ann+Biomed+Eng%22%5BJournal%5D)">High-resolution mapping of in vivo gastrointestinal slow wave activity using flexible printed circuit board electrodes: Methodology and validation.</a> Ann Biomed Eng. 37, 839-846 (2009).</li>
<li>JoVE Science Education Database. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Neuroscience.+Histological+Staining+of+Neural+Tissue%5BTitle%5D)+AND+%22JoVE%22%5BJournal%5D)">Neuroscience. Histological Staining of Neural Tissue.</a> JoVE. , (2023).</li>
</ol>

The authors have nothing to disclose.

The protocol presented here outlines the procedure for constructing a customized headstage specifically designed for the simultaneous recording of dual local field potentials (LFPs) in the hippocampus (HIP) and the prefrontal cortex (PFC). The detailed steps provided in this protocol offer sufficient information for researchers to thoroughly examine signal communication both within each region and between the HIP and PFC.
The custom-designed headstage utilizes a commercial amplifier chip. Whil...

Local field potentials (LFPs) refer to the electrical activity recorded from the extracellular space, reflecting the collective activity of a localized group of neurons. They exhibit a diverse range of frequencies, spanning from slow waves at 1 Hz to fast oscillations at 100 Hz or 200 Hz. Specific frequency bands have been associated with cognitive functions such as learning, memory, and decision making1,2. Changes in LFP properties have been used as biomarkers for various neurological disorders, including dementia and schizophrenia3,4. Analyzing LFP recordings can offer valuable insights into the underlying pathological mechanisms associated with these conditions and potential therapeutic strategies.
Dual LFP recording is a technique used to measure localized electrical activity within and between two specific brain regions. This technique provides a valuable opportunity to investigate the intricate neural dynamics and signal communication occurring within and between distinct brain regions. Prior studies have revealed that detecting alterations in the neuronal properties of individual brain regions can be complex, but changes in interregional cortical communication can be observed5,6. Therefore, the utilization of dual LFP recording offers a potent means to address this issue.
Hippocampal-prefrontal connectivity plays a crucial role in modulating cognitive functions, and dysfunction has been linked to various neurological disorders7,8. Dual electrode recordings of these regions can provide information about these interactions. Unfortunately, there is limited information available on methods for performing dual electrode LFP recordings between these areas. Moreover, commercially available recording devices are generally expensive and lack adaptability to specific experimental designs. The conventional method for recording LFPs involves using a shielded cable to connect the recording device to electrodes implanted in an animal's brain. However, this approach is susceptible to motion artifacts and environmental noise, impacting the quality and reliability of the recorded signals.
This protocol describes a comprehensive procedure for performing dual-electrode LFP recordings in the mouse hippocampus and prefrontal cortex, using a low-cost custom-designed headstage that can be placed on the animal's head. These methods enable researchers to investigate region-specific oscillatory patterns within two discrete cerebral regions and explore interregional information exchange and connectivity between these areas.

<table><tbody><tr><td>Brass tube&amp;nbsp;</td><td>Albion Alloys, USA</td><td>Inside diameter of 0.45 mm</td><td></td></tr><tr><td>Carprofen&amp;nbsp;</td><td>Rimadyl, Pfizer Animal Health&amp;nbsp;</td><td></td><td></td></tr><tr><td>Commercial amplifier chip</td><td>Intantech</td><td>RHD 2132</td><td></td></tr><tr><td>Control board</td><td>Intantech</td><td>RHD recording system</td><td></td></tr><tr><td>Dental cement&amp;nbsp;</td><td>Paladur</td><td></td><td></td></tr><tr><td>Heat shrinks</td><td>Panduit</td><td>0.8 mm diameter</td><td></td></tr><tr><td>M1.2 stainless steel screw</td><td>Watch tools</td><td>Clock and watch screw</td><td></td></tr><tr><td>Multichannel socket connector&amp;nbsp;</td><td>Harwin, AU</td><td>1.27 mm pitch, PCB socket</td><td></td></tr><tr><td>PFA-coated tungsten wires&amp;nbsp;</td><td>A-M SYSTEMS, USA</td><td>Inside diameter of 150 &amp;micro;m&amp;nbsp;</td><td></td></tr><tr><td>Phosphoric acid-based flux</td><td>Chip Quik</td><td>CQ4LF-0.5</td><td></td></tr><tr><td>Recording software</td><td>Intantech</td><td>RHX recording software</td><td></td></tr><tr><td>Stereotactic Frame</td><td>World Precision Instruments</td><td>Mouse stereotactic instrument</td><td></td></tr><tr><td>Super glue</td><td>UHU</td><td>Ultra fast</td><td></td></tr></tbody></table>

dual extracellular recordings in the mouse hippocampus and prefrontal cortex

The technique of recording local field potentials (LFPs) is an electrophysiological method used to measure the electrical activity of localized neuronal populations. It serves as a crucial tool in cognitive research, particularly in brain regions like the hippocampus and prefrontal cortex. Dual LFP recordings between these areas are of particular interest as they allow the exploration of interregional signal communication. However, methods for performing these recordings are rarely described, and most commercial recording devices are either expensive or lack adaptability to accommodate specific experimental designs. This study presents a comprehensive protocol for performing dual-electrode LFP recordings in the mouse hippocampus and the prefrontal cortex to investigate the effects of antipsychotic drugs and potassium channel modulators on LFP properties in these areas. The technique enables the measurement of LFP properties, including power spectra within each brain region and coherence between the two. Additionally, a low-cost, custom-designed recording device has been developed for these experiments. In summary, this protocol provides a means to record signals with high signal-to-noise ratios in different brain regions, facilitating the investigation of interregional information communication within the brain.

The results shown here demonstrate the effects of several drugs on local field potentials (LFPs) properties tested in four cohorts of C57BL/6 male mice (n = 8 for each cohort; age: 8 weeks; weight: 24.0 &#177; 0.42 g). The drugs tested included the antipsychotic drug clozapine, the potassium channel modulators 4-Aminopyridine (4-AP), and retigabine, as well as the control vehicle saline.
As shown in Figure 1, the mouse was placed in a small recording chamber and L...

Watch this Scientific Journal Video about Dual Extracellular Recordings in the Mouse Hippocampus and Prefrontal Cortex at JoVE.com

Author Spotlight: Studying Drug Impacts on Brain Signals Using Dual LFP Recording Protocol in Mice

This protocol outlines the use of a custom-designed recording device and electrodes to record local field potentials and investigate information flow in the mouse hippocampus and prefrontal cortex.

Dual Extracellular Recordings in the Mouse Hippocampus and Prefrontal Cortex

The technique of recording local field potentials (LFPs) is an electrophysiological method used to measure the electrical activity of localized neuronal ...

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1.5K Views.  The University of Melbourne. This protocol outlines the use of a custom-designed recording device and electrodes to record local field potentials and investigate information flow in the mouse hippocampus and prefrontal cortex.

Video: Author Spotlight: Studying Drug Impacts on Brain Signals Using Dual LFP Recording Protocol in Mice

Dual Electrophysiological Recordings of Synaptically-evoked Astroglial and Neuronal Responses in Acute Hippocampal Slices

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs through activation of their ion channels and neurotransmitter receptors, and process information in part through activity-dependent release of gliotransmitters. Furthermore, astrocytes constitute the main uptake system for glutamate, contribute to potassium spatial buffering, as well as to GABA clearance. These cells therefore constantly monitor synaptic activity, and are thereby sensitive indicators for alterations in synaptically-released glutamate, GABA and extracellular potassium levels. Additionally, alterations in astroglial uptake activity or buffering capacity can have severe effects on neuronal functions, and might be overlooked when characterizing physiopathological situations or knockout mice. Dual recording of neuronal and astroglial activities is therefore an important method to study alterations in synaptic strength associated to concomitant changes in astroglial uptake and buffering capacities. Here we describe how to prepare hippocampal slices, how to identify stratum radiatum astrocytes, and how to record simultaneously neuronal and astroglial electrophysiological responses. Furthermore, we describe how to isolate pharmacologically the synaptically-evoked astroglial currents.

The preparation of acute brain slices from isolated hippocampi, as well as the simultaneous electrophysiological recordings of astrocytes and neurons in stratum radiatum during stimulation of schaffer collaterals is described. The pharmacological isolation of astroglial potassium and glutamate transporter currents is demonstrated.

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs ...

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 ...

Double-barreled and Concentric Microelectrodes for Measurement of Extracellular Ion Signals in Brain Tissue

Electrical activity in the brain is accompanied by significant ion fluxes across membranes, resulting in complex changes in the extracellular concentration of all major ions. As these ion shifts bear significant functional consequences, their quantitative determination is often required to understand the function and dysfunction of neural networks under physiological and pathophysiological conditions. In the present study, we demonstrate the fabrication and calibration of double-barreled ion-selective microelectrodes, which have proven to be excellent tools for such measurements in brain tissue. Moreover, so-called &#8220;concentric&#8221; ion-selective microelectrodes are also described, which, based on their different design, offer a far better temporal resolution of fast ion changes. We then show how these electrodes can be employed in acute brain slice preparations of the mouse hippocampus. Using double-barreled, potassium-selective microelectrodes, changes in the extracellular potassium concentration ([K+]o) in response to exogenous application of glutamate receptor agonists or during epileptiform activity are demonstrated. Furthermore, we illustrate the response characteristics of sodium-sensitive, double-barreled and concentric electrodes and compare their detection of changes in the extracellular sodium concentration ([Na+]o) evoked by bath or pressure application of drugs. These measurements show that while response amplitudes are similar, the concentric sodium microelectrodes display a superior signal-to-noise ratio and response time as compared to the double-barreled design. Generally, the demonstrated procedures will be easily transferable to measurement of other ions species, including pH or calcium, and will also be applicable to other preparations.

We demonstrate the fabrication, calibration and properties of two types of ion-selective microelectrodes (double-barreled and concentric) for measurement of ion concentrations in brain tissue. These are then used in the mouse hippocampal slice preparation to show that excitatory activity changes both extracellular potassium and sodium concentrations.

Electrical activity in the brain is accompanied by significant ion fluxes across membranes, resulting in complex changes in the extracellular ...

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 ...

Recording Spatially Restricted Oscillations in the Hippocampus of Behaving Mice

The local field potential (LFP) emerges from ion movements across neural membranes. Since the voltage recorded by LFP electrodes reflects the summed electrical field of a large volume of brain tissue, extracting information about local activity is challenging. Studying neuronal microcircuits, however, requires a reliable distinction between truly local events and volume-conducted signals originating in distant brain areas. Current source density (CSD) analysis offers a solution for this problem by providing information about current sinks and sources in the vicinity of the electrodes. In brain areas with laminar cytoarchitecture such as the hippocampus, one-dimensional CSD can be obtained by estimating the second spatial derivative of the LFP. Here, we describe a method to record multilaminar LFPs using linear silicon probes implanted into the dorsal hippocampus. CSD traces are computed along individual shanks of the probe. This protocol thus describes a procedure to resolve spatially restricted neuronal network oscillations in the hippocampus of freely moving mice.

This protocol describes the recording of local field potentials with multi-shank linear silicon probes. Conversion of the signals using current source density analysis allows the reconstruction of local electrical activity in the mouse hippocampus. With this technique, spatially restricted brain oscillations can be studied in freely moving mice.

The local field potential (LFP) emerges from ion movements across neural membranes. Since the voltage recorded by LFP electrodes reflects the summed ...

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 ...

Extracellular Electrophysiological Recording in the Motor Cortex of Mice

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.

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.

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

Recording of Local Field Potential in Mouse Hippocampal-Entorhinal Cortex Slices

Source: Whitebirch, A. C. <a href="https://app.jove.com/v/61704">Acute Mouse Brain Slicing to Investigate Spontaneous Hippocampal Network Activity.</a> J. Vis. Exp. (2020)
The video demonstrates a procedure to record the local field potential (LFP) in mouse hippocampal-entorhinal cortex slices. Electrical stimulation is provided at the CA3 stratum radiatum of the hippocampus, which causes changes in the postsynaptic potential at the CA1 stratum pyramidale. The combined change in the membrane potential of CA1 neurons, termed the local field potential, is recorded.

All procedures involving sample collection have been performed in accordance with the institute&#39;s IRB guidelines.
1. Transcardial perfusion

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Electrophysiology Techniques

Recording of Local Field Potential from Both Hemispheres of the Mouse Brain

Source: Chen, Y., et al. <a href="https://app.jove.com/v/59310">Evaluation of Hemisphere Lateralization with Bilateral Local Field Potential Recording in Secondary Motor Cortex of Mice.</a> J. Vis. Exp. (2019).
This video demonstrates in vivo recording of local field potential (LFP) from bilateral M2 areas of the mouse brain. An anesthetized mouse is secured and prepared for the procedure. To record LFPs, insert microelectrodes into the target coordinates of the bilateral M2 areas, which are responsible for complex motor movements.

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

Recording Neuronal Field Excitatory Postsynaptic Potentials in Acute Hippocampal Slices

Source: Weng, W., et al. <a href="https://app.jove.com/v/55936">Recording Synaptic Plasticity in Acute Hippocampal Slices Maintained in a Small-volume Recycling-, Perfusion-, and Submersion-type Chamber System.</a> J. Vis. Exp. (2018).
This video demonstrates the procedure for setting up a brain slice in a submersion chamber to record synaptic activity. The process involves securing the slice on lens paper, maintaining a continuous flow of artificial cerebrospinal fluid (aCSF) to ensure neuronal viability, and accurately positioning the stimulation and recording electrodes relative to a specific brain region of interest. This setup allows for precise monitoring of baseline synaptic activity and the effects of electrical stimulation.