This research was supported by the National Natural Science Foundation of China (31871085), the Natural Science Foundation of Shanghai (21ZR1407300), the Shanghai Municipal Science and Technology Major Project (2018SHZDZX01), ZJ Lab, and Shanghai Center for Brain Science and Brain-Inspired Technology.

This protocol received approval from the Animal Care and Use Committee at Fudan University and was conducted following the guidelines and regulations designed by the National Institutes of Health Guide for Care and Use of Laboratory Animals. All possible measures were implemented to minimize the number of animals utilized in this study. The time required to perform each step is included in the respective steps.
1. Preparation of electrodes (Figure 1)
<ol>
	<li>Cut an appropriate length of tungsten wire (~20 mm) and burn off the insulation layer at one end to expose the tungsten wire (1.6-2 mm). Bend the other end of the wire into an &#34;L&#34; shape (see Figure 1A, ~1 min)</li>
	<li>Carefully place the &#34;L&#34; end of the tungsten wire onto the optical fiber (see Figure 1B, ~1 min). 
	NOTE: The tungsten wire should be 0.2-0.4 mm longer than the tip of optical fiber.</li>
	<li>Dip a drop of adhesive and apply it to the interface of the optical fiber and the tungsten wire (see Figure 1C, ~1 min). Due to the surface tension of the liquid, the tungsten wire will attach to the optical fiber.</li>
	<li>Apply the adhesive once and allow it to dry. Then, apply a second coat. This will further tighten the bond between the tungsten wire and the optical fiber (see Figure 1C, ~1 min). 
	NOTE: During the application process, care should be taken to prevent the adhesive from flowing to the tip of the optical fiber, as this may affect its transmittance.</li>
	<li>At the corner of the &#34;L&#34; shape, use adhesive to closely bond the base of the optical fiber and the tungsten wire together (~1 min). 
	NOTE: The increased contact area and the spherical solidification of the adhesive droplet ensure a firm bond between the optical fiber and the tungsten wire.</li>
	<li>Use soldering to establish a connection between the tungsten wire and the pin of the female connector (see Figure 1D, ~3 min for each) 
	NOTE: Since tungsten wire is not sensitive to heat, the success rate of soldering can be increased to nearly 100% by a metal sleeve fashioned by cutting the pin slot location to physically unite the two components. Subsequently, solder filling the sleeve ensures a stable connection between the inserted tungsten wire and the pin.</li>
	<li>According to the experimental design, solder the required number of optrodes (see Figure 1E, ~10 min) 
	NOTE: Three optrodes were utilized in this study.</li>
	<li>Cut the enameled wire to the appropriate length (~30 mm) and burn off the insulation on both ends. Wrap one end of the enameled wire around the base of the screw and solder it. Connect the other end of the enameled wire to the pins of the female connector via a soldering iron, serving as the EEG recording and ground connection for the skull electrode (see Figure 1F, ~5 min) 
	NOTE: Due to the flexibility of the enameled wire, it is convenient to connect the skull and the pins of the female connector. Soldering after winding the enameled wire around a screw is more reliable than surface-mount soldering.</li>
	<li>Apply hot-melt adhesive to the female connector&#39;s pin array to encapsulate the female connector and ensure the solder joints are fully enveloped. During the solidification of the hot-melt adhesive, shape the adhesive using a plastic board to minimize space occupancy during implantation (see Figure 1F, ~3 min) 
	NOTE: Due to the potential burn risks associated with using hot-melt glue, AB adhesive is considered a safer alternative.</li>
	<li>Next, use a light intensity meter and digital multimeter to measure luminousness and conductivity. Upon passing these tests, the setup is ready for use (see Figure 1G, ~2 min) 
	NOTE: When working with lasers, always wear protective eyewear suitable for the specific wavelength and power of the laser light. High-quality fibers are required to transmit at least 80% of the light from the end of the patch cord to the tip of the implantable fiber. Additionally, the resistance from the tip of the tungsten wire to the pin header slot was measured with an acceptable range of 1-5 &#937;.</li>
	<li>Before use, immerse the prepared electrodes in 75% alcohol for 15 min, then transfer them to sterile saline (~16 min). 
	NOTE: The total weight of the encapsulated electrode device (0.6701 &#177; 0.01123 g, n = 4) does not affect the activity of the mice. The electrodes are sterilized in advance using plasma sterilization.</li>
</ol>
2. Protocol for electrode implantation (Figure 2)
<ol>
	<li>Anesthetize the mice with isoflurane (2%-4%) and secure them in a stereotaxic apparatus (see Figure 2A, ~2 min). Use eye ointment on mouse eyes to prevent dryness while under anesthesia. Apply lidocaine to the skin around the perimeter of the cranial incision and a subcutaneous injection of carprofen at a dose of 5 mg/kg. 
	NOTE: Proper anesthetization is confirmed through the absence of the righting reflex and the loss of response to toe pinch. For prolonged surgical procedures, using an injectable&#160;anesthetic is more appropriate.</li>
	<li>After securing the animal in the stereotaxic apparatus, trim away the scalp along the edge of the skull and wipe the skull surface with 75% alcohol to expose the positions of the bregma and lambda (see Figure 2B, ~3 min). 
	NOTE: The pre-surgical procedure includes clipping the hair, disinfecting the surgical site, pre-sterilizing the instruments and surgical tools.</li>
	<li>Level the brain and drill holes (~0.8 mm) above the regions of interest (ROI) using a microdrill. Inject the relevant viruses with a syringe pump (see Figure 2C - F, ~20 min). 
	NOTE: Detailed information about the viruses and ROIs in this study is shown in the Table of Materials and Figure 3.</li>
	<li>Hold the optrodes with a holder and move their tip to the bregma point, setting this position as &#39;zero&#39;. Using the bregma point as the reference coordinate, move the optrodes to the target regions (see Figure 2G, ~3 min). Position the optrodes 0.3 mm above the virus injection site. 
	NOTE: In the vertical implantation strategy, the minimum&#160;distance between the two electrodes is approximately 2 mm, depending on the thickness of the fiber optic sleeve and the outer diameter of the ferrule. An angled insertion method can be used for simultaneous recording from closely located regions.</li>
	<li>After inserting the optic fibers into the corresponding brain areas, apply a small amount of tissue adhesive around them to cover the exposed tissue. Then, sequentially apply additional adhesive and a little dental cement. After the dental cement solidifies, release the holder carefully (see Figure 2H, ~5 min).</li>
	<li>Before each new optrode implantation, perform recalibration, which involves repeating step 2.4 (see Figure 2I). 
	NOTE: For each implantation, position the optrode at bregma as the &#39;zero&#39; point.</li>
	<li>After implanting all optrodes, drill the holes behind the lambda point for &#39;Ground&#39; and above the neocortex for &#39;EEG&#39; using a microdrill (~1 min). 
	NOTE: The size of the drilled hole (~1.1 mm) needs to match the diameter of the screw.</li>
	<li>Insert skull screws into the hole above the cortex and behind the lambda point (see Figure 2J, ~5 min). 
	NOTE: Skull screws are used for EEG recording and grounding, respectively.</li>
	<li>Organize the tungsten wires and enameled wires so they are positioned above the implantation area and not exposed outside the skull. Secure the position of the female connector using a holder (see Figure 2K, ~2 min).</li>
	<li>Fill the implantation site with dental cement to ensure a stable connection between the electrode device and the skull. Encapsulate the internal wires, leaving the female connector&#39;s insertion holes exposed for connection to the headstage (see Figure 2L, ~6 min).</li>
	<li>After dental cement hardening, apply iodine to the skin around the perimeter of the exposed scalp and then place the animal on a warming pad (~1 min). 
	NOTE: Ensure that the animal is not left unattended until it has regained sufficient consciousness to maintain sternal recumbency. Sterile conditions should be maintained throughout the survival surgery.</li>
	<li>Administer antibiotics and analgesics to support post-surgical recovery. 
	NOTE: Animals that have undergone surgery are not reintroduced to the company of other animals until they have fully recovered.Animals were administered intraperitoneal injections of ceftriaxone sodium (180 mg/kg),&#160;and subcutaneous injections of carprofen (5 mg/kg),&#160;and lidocaine gel was applied to the surgical wounds daily for 3 days. The animals are required to survive for a designated period to complete the behavioral testing. Subsequently, they will be euthanized using 4%-5% isoflurane, followed by perfusion and tissue sectioning to assess viral infection and the sites of electrode implantation.</li>
</ol>
3. Protocol for recording in vivo brain
<ol>
	<li>Before conducting signal recording and behavioral testing (open field test)15, ensure that the mouse undergoes a 3-day period of gentle handling to acclimatize them to the environment. 
	NOTE: In this study, the mice were placed in an open field (42 cm &#215; 42 cm) to move around freely, allowing us to observe their seizure behavior.</li>
	<li>After anesthetizing the mice with isoflurane (2%-4%), connect the optical fibers sequentially in the order of the recording site before inserting the headstage.</li>
	<li>Set the 635 nm light pulse with a 10% duty cycle at 20 Hz. Set up the light stimulation for 10 s (200 pulses) during recording. Set the intensity at the optical fiber tips at 3 mW.</li>
	<li>Use a fiber photometry system to record Gcamp6m signals behavioral testing period at a sampling rate of 30 Hz by 470 nm LED channel.</li>
	<li>Simultaneously record calcium signals, LFPs, and EEG under optogenetic stimulation, along with corresponding behavioral performances (see Figure 3).</li>
	<li>Employ transistor-transistor logic (TTL) signal synchronization tagging to ensure temporal consistency in recorded data.</li>
</ol>
4. Data processing
<ol>
	<li>Load photometry data to MATLAB software. Then, use custom coding (Supplementary File 1) to detrend the calcium signal.</li>
	<li>Define the changes in fluorescence intensity with equation (1): 
	&#916;F/F = (Ft&#160;-&#160;F0)/ F0&#160; &#160; (1) 
	Where Ft represents the real-time calcium signal fluorescence values, and F0 denotes the averaged baseline fluorescence intensity before the event.</li>
	<li>Import the electrophysiological data, sampled rate of 1000 Hz, into MATLAB (Supplementary File 2).</li>
	<li>Coordinate the display of calcium signaling and electrophysiological data in alignment with synchronized markers.</li>
</ol>

Flexible Multi-Region Neural Recording Device for Epilepsy Research

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The authors declare no competing financial interests to disclose.

Here, we employed a self-made optrode device for in vivo neural signal recording across multiple regions. The feasibility of this system for simultaneous optogenetic stimulation, calcium signal recording, and electrophysiological recording has been validated. The electrode preparation method described herein is efficient and cost-effective. According to the experimental design, we could record signals from relevant brain regions. The strategic arrangement of optrodes allows for the potential extraction of abunda...

Epilepsy is a common neurological condition characterized by recurrent seizures, which manifest as convulsions, sensory disturbances, and loss of consciousness1. The pathophysiological mechanisms underlying epilepsy are complex and involve multiple interconnected brain regions2,3. Recent advances in neuroimaging have shed light on the large-scale networks involved in epilepsy4,5. However, understanding of the intricate circuitry and network mechanisms underlying the generation and propagation of epilepsy remains limited, partly due to the insufficient application of multi-region neural recording techniques6. Therefore, developing a flexible, integrated method capable of simultaneously monitoring neural activity across disparate brain regions is imperative.
Electrophysiological recordings are conducted to capture seizures and determine the presence of epilepsy7. Except for recording electrophysiological activity, there is a growing emphasis on the precise calcium activity of specific&#160;neural populations in epilepsy studies8,9. Advancements in calcium indicator synthesis and various probe designs have prompted researchers to adopt fiber photometry for capturing changes in neuronal activity and neural substances within the brain10,11. The two independent methods of detecting neuronal activity, namely electrophysiology and fiber photometry recording, complement each other, facilitating a more comprehensive understanding of dynamic neuronal processes.
Additionally, synchronous recording and modulating neural activity are pivotal for gaining insights into the brain functioning at both network and cellular levels. This approach enables researchers to observe and manipulate the brain&#39;s complex processes in real-time. Optogenetics has emerged as an indispensable tool for probing neural signaling, owing to its distinctive ability for selective stimulation or inhibition12. Despite widespread applications of multi-site electrophysiological recording in neuroscience13, the integration of multi-region electrophysiological recording with fiber photometry and optogenetic manipulation remains limited. More importantly, current methods for fabricating and implanting multi-region electrodes lack flexibility14. These limitations hinder our capacity to dissect specific circuit functions and interactions across multiple regions. Here, we present a cost-effective and convenient multi-region in vivo recording approach that sheds light on neuronal processes across regions in kindling-induced seizures and other neuropsychiatric disorders.

<table><tbody><tr><td>8-32 adapter</td><td>Plexon</td><td>Custom ordered</td><td>Connect the female connector and headstage</td></tr><tr><td>AAV-CaMKII&amp;alpha;-ChrimsonR-mcherry</td><td>Taitool Bioscience</td><td>S0371-9</td><td>4 x 10&lt;sup&gt;12&lt;/sup&gt; VG/mL&amp;nbsp;</td></tr><tr><td>AAV-hsyn-Gcamp6m</td><td>Taitool Bioscience</td><td>S0471-9</td><td>4 x 10&lt;sup&gt;12&lt;/sup&gt; VG/mL&amp;nbsp;</td></tr><tr><td>DAPI</td><td>Sigma</td><td>236276</td><td>Titered 1:500</td></tr><tr><td>Dental Cement</td><td>New Century Dental</td><td>430205</td><td></td></tr><tr><td>Electrophysiological recordings system</td><td>Plexon</td><td>Omniplex</td><td></td></tr><tr><td>Enameled wire</td><td>N/A</td><td>Custom ordered</td><td>Diameter = 0.2 mm</td></tr><tr><td>Female connector</td><td>N/A</td><td>Custom ordered</td><td>1.25 mm pitch</td></tr><tr><td>Glue</td><td>Loctite</td><td>45282</td><td></td></tr><tr><td>Laser</td><td>Changchun New Industries</td><td>BH81563</td><td>635 nm&amp;nbsp;</td></tr><tr><td>MATLAB</td><td>MathWorks</td><td>R2021b</td><td></td></tr><tr><td>Microdrill</td><td>RWD</td><td>78001</td><td></td></tr><tr><td>Multichannel fiber photometry</td><td>ThinkerTech</td><td>FPS-SS-MC-LED</td><td></td></tr><tr><td>Optical fiber</td><td>Xi&#039;an Bogao</td><td>L-200UM</td><td>Select the appropriate fiber length based on the depth of the targeted brain regions.</td></tr><tr><td>PFA-Coated Tungsten wire</td><td>A-M System</td><td>795500</td><td>Bare 0.002&quot;; Coated 0.0040&quot;</td></tr><tr><td>Power meter</td><td>Thorlabs</td><td>PM100D</td><td></td></tr><tr><td>Stereotaxic Fxrame</td><td>RWD</td><td>68807</td><td></td></tr><tr><td>Tissue adhesive</td><td>3M</td><td>1469SB</td><td></td></tr></tbody></table>

an integrated method for crafting flexible and convenient electrophysiological optrodes for multi-region in vivo recording

Epilepsy is a neurological disorder characterized by synchronized abnormal discharges involving multiple brain regions. Focal lesions facilitate the propagation of epileptic signals through associated neural circuits. Therefore, in vivo recording of local field potential (LFP) from the critical brain regions is&#160;essential for deciphering the circuits involved in seizure propagation. However, current methods for electrode fabrication and implantation lack flexibility. Here, we present a handy device designed for electrophysiological recordings (LFPs and electroencephalography [EEG]) across multiple regions. Additionally, we seamlessly integrated optogenetic manipulation and calcium signaling recording with LFP recording. Robust after-discharges were observed in several separate regions during epileptic seizures, accompanied by increasing&#160;calcium signaling. The approach used in this study offers a convenient and flexible strategy for synchronous neural recordings across diverse regions of the brain. It holds the potential for advancing research on neurological disorders by providing insights into the neural profiles of multiple regions involved in these disorders.

We combined optogenetics with multiregional electrophysiological recording and calcium imaging to observe neuronal activity across various brain regions during optogenetic seizures. For this purpose, an adeno-associated virus (AAV) expressing ChrimsonR under the control of the CaMKII&#945; promoter (AAV-CaMKII&#945;-ChrimsonR-mcherry)16 was injected into a classical epileptogenic site, the piriform cortex (ROI 1)17, in rodents. Additionally, AAV-hsyn-Gcamp6m<sup class="xref...

Author Spotlight: Unraveling Neural Communication and Circuit Interactions in Health and Disease

We have developed a simplified and cost-effective approach for electrode fabrication and conducted recordings of signals across multiple regions in freely moving mice. Utilizing optogenetics, alongside multi-region electrophysiology and calcium signal recording, enabled the revelation of neuronal activities across regions in the seizure kindling model.

An Integrated Method for Crafting Flexible and Convenient Electrophysiological Optrodes for Multi-Region In Vivo Recording

Epilepsy is a neurological disorder characterized by synchronized abnormal discharges involving multiple brain regions. Focal lesions facilitate the ...

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Research

JoVE Journal

Neuroscience

659 Views.  Fudan University. We onderzoeken hersennetwerken en neurale circuits met behulp van multimodale benaderingen die technieken omvatten zoals meerkanaals elektrofysiologische opname, vezelfotometrie, neuromodulatie en functionele magnetische resonantiebeelden. We proberen een antwoord te geven op hoe verschillende hersengebieden in vivo communiceren en op elkaar inwerken, zowel in gezonde als in zieke toestanden. We gebruiken methoden voor natuurlijke replicatie en implantatie om...

Video: Auteur in de schijnwerpers: neurale communicatie en circuitinteracties in gezondheid en ziekte ontrafelen

Electrode Fabrication and Implantation in Aplysia californica for Multi-channel Neural and Muscular Recordings in Intact, Freely Behaving Animals

Recording from key nerves and muscles of Aplysia during feeding behavior allows us to study the patterns of neural control in an intact animal. Simultaneously recording from multiple nerves and muscles gives us precise information about the timing of neural activity. Previous recording methods have worked for two electrodes, but the study of additional nerves or muscles required combining and averaging the recordings of multiple animals, which made it difficult to determine fine details of timing and phasing, because of variability from response to response, and from animal to animal. Implanting four individual electrodes has a very low success rate due to the formation of adhesions that prevent animals from performing normal feeding movements. We developed a new method of electrode fabrication that reduces the bulk of the electrodes inside the animal allowing for normal feeding movements. Using a combination of glues to attach the electrodes results in a more reliable insulation of the electrode which lasts longer, making it possible to record for periods as long as a week. The fabrication technique that we describe could be extended to incorporate several additional electrodes, and would be applicable to vertebrate animals.

Electrode Fabrication and Implantation in Aplysia californica for Multi-channel Neural and Muscular Recordings in Intact, Freely Behaving Animals

A technique is described for implanting four in vivo electrodes to monitor the neuromuscular control of feeding behavior in Aplysia californica.

Recording from key nerves and muscles of Aplysia during feeding behavior allows us to study the patterns of neural control in an intact animal.  ...

A Method for Systematic Electrochemical and Electrophysiological Evaluation of Neural Recording Electrodes

New materials and designs for neural implants are typically tested separately, with a demonstration of performance but without reference to other implant characteristics.&#160;This precludes a rational selection of a particular implant as optimal for a particular application and the development of new materials based on the most critical performance parameters.&#160;This article develops a protocol for in vitro and in vivo testing of neural recording electrodes.&#160;Recommended parameters for electrochemical and electrophysiological testing are documented with the key steps and potential issues discussed.&#160;This method eliminates or reduces the impact of many systematic errors present in simpler in vivo testing paradigms, especially variations in electrode/neuron distance and between animal models.&#160;The result is a strong correlation between the critical in vitro and in vivo responses, such as impedance and signal-to-noise ratio.&#160;This protocol can easily be adapted to test other electrode materials and designs.&#160;The in vitro techniques can be expanded to any other nondestructive method to determine further important performance indicators.&#160;The principles used for the surgical approach in the auditory pathway can also be modified to other neural regions or tissue.

Different electrode coatings affect neural recording performance through changes to electrochemical, chemical and mechanical properties. Comparison of electrodes in vitro is relatively simple, however comparison of in vivo response is typically complicated by variations in electrode/neuron distance and between animals. This article provides a robust method to compare neural recording electrodes.

New materials and designs for neural implants are typically tested separately, with a demonstration of performance but without reference to other implant ...

A Guide to In vivo Single-unit Recording from Optogenetically Identified Cortical Inhibitory Interneurons

A major challenge in neurophysiology has been to characterize the response properties and function of the numerous inhibitory cell types in the cerebral cortex. We here share our strategy for obtaining stable, well-isolated single-unit recordings from identified inhibitory interneurons in the anesthetized mouse cortex using a method developed by Lima and colleagues1. Recordings are performed in mice expressing Channelrhodopsin-2 (ChR2) in specific neuronal subpopulations. Members of the population are identified by their response to a brief flash of blue light. This technique &#8211; termed &#8220;PINP&#8221;, or Photostimulation-assisted Identification of Neuronal Populations &#8211; can be implemented with standard extracellular recording equipment. It can serve as an inexpensive and accessible alternative to calcium imaging or visually-guided patching, for the purpose of targeting extracellular recordings to genetically-identified cells. Here we provide a set of guidelines for optimizing the method in everyday practice. We refined our strategy specifically for targeting parvalbumin-positive (PV+) cells, but have found that it works for other interneuron types as well, such as somatostatin-expressing (SOM+) and calretinin-expressing (CR+) interneurons.

A Guide to In vivo Single-unit Recording from Optogenetically Identified Cortical Inhibitory Interneurons

Here we describe our strategy for obtaining stable, well-isolated single-unit recordings from identified inhibitory interneurons in the anesthetized mouse cortex. Neurons expressing ChR2 are identified by their response to blue light. The method uses standard extracellular recording equipment, and serves as an inexpensive alternative to calcium imaging or visually-guided patching.

A major challenge in neurophysiology has been to characterize the response properties and function of the numerous inhibitory cell types in the cerebral ...

Simultaneous Electrophysiological Recording and Micro-injections of Inhibitory Agents in the Rodent Brain

Here we describe a method for the construction of a single-use &#8220;injectrode&#8221; using commercially accessible and affordable parts. A probing system was developed that allows for the injection of a drug while recording electrophysiological signals from the affected neuronal population. This method provides a simple and economical alternative to commercial solutions. A glass pipette was modified by combining it with a hypodermic needle and a silver filament. The injectrode is attached to commercial microsyringe pump for drug delivery. This results in a technique that provides real-time pharmacodynamics feedback through multi-unit extracellular signals originating from the site of drug delivery. As a proof of concept, we recorded neuronal activity from the superior colliculus elicited by flashes of light in rats, concomitantly with delivery of drugs through the injectrode. The injectrode recording capacity permits the functional characterization of the injection site favoring precise control over the localization of drug delivery. Application of this method also extends far beyond what is demonstrated here, as the choice of chemical substance loaded into the injectrode is vast, including tracing markers for anatomic experiments.

Here, we craft a glass pipette with dual functions: inhibition of deep brain structures by microinjections of drugs and real-time monitoring of their effects through simultaneous electrophysiological recordings.

Here we describe a method for the construction of a single-use &#8220;injectrode&#8221; using commercially accessible and affordable parts. A probing ...

Chronic Implantation of Multiple Flexible Polymer Electrode Arrays

Simultaneous recordings from large populations of individual neurons across distributed brain regions over months to years will enable new avenues of scientific and clinical development. The use of flexible polymer electrode arrays can support long-lasting recording, but the same mechanical properties that allow for longevity of recording make multiple insertions and integration into a chronic implant a challenge. Here is a methodology by which multiple polymer electrode arrays can be targeted to a relatively spatially unconstrained set of brain areas.
The method utilizes thin-film polymer devices, selected for their biocompatibility and capability to achieve long-term and stable&#160;electrophysiologic recording interfaces. The resultant implant allows accurate and flexible targeting of anatomically distant regions, physical stability for months, and robustness to electrical noise. The methodology supports up to sixteen serially inserted devices across eight different anatomic targets. As previously demonstrated, the methodology is capable of recording from 1024 channels. Of these, the 512 channels in this demonstration used for single neuron recording yielded 375 single units distributed across six recording sites. Importantly, this method also can record single units for at least 160 days.
This implantation strategy, including temporarily bracing each device with a retractable silicon insertion shuttle, involves tethering of devices at their target depths to a skull-adhered plastic base piece that is custom-designed for each set of recording targets, and stabilization/protection of the devices within a silicone-filled, custom-designed plastic case. Also covered is the preparation of devices for implantation, and design principles that should guide adaptation to different combinations of brain areas or array designs.

Described below is a method for implantation of multiple polymer electrode arrays across anatomically distant brain regions for chronic electrophysiological recording in freely moving rats. Preparation and surgical implantation are described in detail, with emphasis on design principles to guide adaptation of these methods for use in other species.

Simultaneous recordings from large populations of individual neurons across distributed brain regions over months to years will enable new avenues of ...

Construction and Implementation of Carbon Fiber Microelectrode Arrays for Chronic and Acute In Vivo Recordings

Multichannel electrode arrays offer insight into the working brain and serve to elucidate neural processes at the single-cell and circuit levels. Development of these tools is crucial for understanding complex behaviors and cognition and for advancing clinical applications. However, it remains a challenge to densely record from cell populations stably and continuously over long time periods. Many popular electrodes, such as tetrodes and silicon arrays, feature large cross-diameters that produce damage upon insertion and elicit chronic reactive tissue responses associated with neuronal death, hindering the recording of stable, continuous neural activity. In addition, most wire bundles exhibit broad spacing between channels, precluding simultaneous recording from a large number of cells clustered in a small area. The carbon fiber microelectrode arrays described in this protocol offer an accessible solution to these concerns. The study provides a detailed method for fabricating carbon fiber microelectrode arrays that can be used for both acute and chronic recordings in vivo. The physical properties of these electrodes make them ideal for stable and continuous long-term recordings at high cell densities, enabling the researcher to make robust, unambiguous recordings from single units across months.

Construction and Implementation of Carbon Fiber Microelectrode Arrays for Chronic and Acute In Vivo Recordings

This protocol describes a procedure for constructing carbon fiber microelectrode arrays for chronic and acute in vivo electrophysiological recordings in mouse (Mus musculus) and ferret (Mustela putorius furo) from multiple brain regions. Each step, following the purchase of raw carbon fibers to microelectrode array implantation, is described in detail, with emphasis on microelectrode array construction.

Multichannel electrode arrays offer insight into the working brain and serve to elucidate neural processes at the single-cell and circuit levels. ...

Optrode Array for Simultaneous Optogenetic Modulation and Electrical Neural Recording

During the last decade, optogenetics has become an essential tool for the investigation of neural signaling due to its unique capability of selective neural modulation or monitoring. As specific types of neuronal cells can be genetically modified to express opsin proteins, optogenetics enables optical stimulation or inhibition of the selected neurons. There have been several technological advances in the optical system for optogenetics. Recently, it was proposed to combine the optical waveguide for light delivery with electrophysiological recording to simultaneously monitor the neural responses to optogenetic stimulation or inhibition. In this study, an implantable optrode array (2x2 optical fibers) was developed with embedded multichannel electrodes. 
A light-emitting diode (LED) was employed as a light source, and a microfabricated microlens array was integrated to provide sufficient light power at the tip of the optical fibers. The optrode array system comprises the disposable part and the reusable part. The disposable part has optical fibers and electrodes, while the reusable part has the LED and electronic circuitry for light control and neural signal processing. The novel design of the implantable optrode array system is introduced in the accompanying video in addition to the procedure of the optrode implantation surgery, optogenetic light stimulation, and the electrophysiological neural recording. The results of in vivo experiments successfully showed time-locked neural spikes evoked by the light stimuli from hippocampal excitatory neurons of mice.

Here, we present the fabrication method of an optrode system with optical fibers for light delivery and an electrode array for neural recording. In vivo experiments with transgenic mice expressing channelrhodopsin-2 show the feasibility of the system for simultaneous optogenetic stimulation and electrophysiological recording.

During the last decade, optogenetics has become an essential tool for the investigation of neural signaling due to its unique capability of selective ...

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.

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.

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

Open&#45;Source Implant for Multi&#45;Region Electrophysiological Monitoring in Rats

The TD Drive: A Parametric, Open-Source Implant for Multi&#45;Area Electrophysiological Recordings in Behaving and Sleeping Rats

Intricate interactions between multiple brain areas underlie most functions attributed to the brain. The process of learning, as well as the formation and consolidation of memories, are two examples that rely heavily on functional connectivity across the brain. In addition, investigating hemispheric similarities and/or differences goes hand in hand with these multi-area interactions. Electrophysiological studies trying to further elucidate these complex processes thus depend on recording brain activity at multiple locations simultaneously and often in a bilateral fashion. Presented here is a 3D-printable implant for rats, named TD Drive, capable of symmetric, bilateral wire electrode recordings, currently in up to ten distributed brain areas simultaneously. The open-source design was created employing parametric design principles, allowing prospective users to easily adapt the drive design to their needs by simply adjusting high-level parameters, such as anterior-posterior and mediolateral coordinates of the recording electrode locations. The implant design was validated in n = 20 Lister Hooded rats that performed different tasks. The implant was compatible with tethered sleep recordings and open field recordings (Object Exploration) as well as wireless recording in a large maze using two different commercial recording systems and headstages. Thus, presented here is the adaptable design and assembly of a new electrophysiological implant, facilitating fast preparation and implantation.

Author Spotlight: Deciphering Memory and Learning Through Neural Implants for Multi&#45;Region Brain Studies

Here, we present a unique, 3D-printable implant for rats, named TD Drive, capable of symmetric, bilateral wire electrode recordings, currently in up to ten distributed brain areas simultaneously.

Intricate interactions between multiple brain areas underlie most functions attributed to the brain. The process of learning, as well as the formation and ...

A Cost-Effective, Versatile Probe Implant System for Electrophysiology in Mice

The DREAM Implant: A Lightweight, Modular, and Cost-Effective Implant System for Chronic Electrophysiology in Head-Fixed and Freely Behaving Mice

Chronic electrophysiological recordings in rodents have significantly improved our understanding of neuronal dynamics and their behavioral relevance. However, current methods for chronically implanting probes present steep trade-offs between cost, ease of use, size, adaptability, and long-term stability.
This protocol introduces a novel chronic probe implant system for mice called the DREAM (Dynamic, Recoverable, Economical, Adaptable, and Modular), designed to overcome the trade-offs associated with currently available options. The system provides a lightweight, modular and cost-effective solution with standardized hardware elements that can be combined and implanted in straightforward steps and explanted safely for recovery and multiple reuse of probes, significantly reducing experimental costs.
The DREAM implant system integrates three hardware modules: (1) a microdrive that can carry all standard silicon probes, allowing experimenters to adjust recording depth across a travel distance of up to 7 mm; (2) a three-dimensional (3D)-printable, open-source design for a wearable Faraday cage covered in copper mesh for electrical shielding, impact protection, and connector placement, and (3) a miniaturized head-fixation system for improved animal welfare and ease of use. The corresponding surgery protocol was optimized for speed (total duration: 2 h), probe safety, and animal welfare.
The implants had minimal impact on animals&#39; behavioral repertoire, were easily applicable in freely moving and head-fixed contexts, and delivered clearly identifiable spike waveforms and healthy neuronal responses for weeks of post-implant data collection. Infections and other surgery complications were extremely rare.
As such, the DREAM implant system is a versatile, cost-effective solution for chronic electrophysiology in mice, enhancing animal well-being, and enabling more ethologically sound experiments. Its design simplifies experimental procedures across various research needs, increasing accessibility of chronic electrophysiology in rodents to a wide range of research labs.

Here, we introduce a lightweight, cost-effective probe implant system for chronic electrophysiology in rodents optimized for ease of use, probe recovery, experimental versatility, and compatibility with behavior.

Chronic electrophysiological recordings in rodents have significantly improved our understanding of neuronal dynamics and their behavioral relevance. ...

An Integrated Method for Crafting Flexible and Convenient Electrophysiological Optrodes for Multi-Region In Vivo Recording

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