We thank Ms. Charu Reddy and Professor Matteo Carandini (Cortex Lab) for their advice on surgical protocol and sharing of transgenic mouse strain. We thank Dr Norbert Hogrefe (Inscopix) for his guidance and assistance through the development of the surgery. We thank Ms Andreea Aldea (Sun Lab) for her assistance with the surgical setup and data processing. This work was supported by the Moorfields Eye Charity.

Multilayer Imaging with Microprism in Head-Fixed and Freely Moving Animals

<ol>
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The authors declare no competing financial interest or conflict of interest.

Here, we have shown the ability to observe and directly compare neurons in head-fixed and freely moving conditions in the same neural populations. While we demonstrated the application in the visual cortex, this protocol can be adapted to a multitude of other brain areas, both cortical areas and deep nuclei24,25,26,27,28, as well as other data acquisition and ...

The advent of in vivo two-photon fluorescent imaging1,2, combining the new technologies in optical systems and genetically modified fluorescence indicators, has emerged as a powerful technique in neuroscience to investigate the intricate structure, function, and plasticity in the living brain3,4. In particular, this imaging modality offers an unparalleled advantage over traditional electrophysiology by capturing both the morphology and dynamic activities of neurons, thereby facilitating long-term tracking of identified neurons5,6,7,8.
Despite its noteworthy strengths, the application of high-resolution fluorescence imaging often necessitates a static, head-fixed setup that constrains the animal&#39;s mobility9,10,11. Additionally, the use of a transparent glass surface for visualizing neurons restricts observations to one or more horizontal planes, limiting the exploration of the dynamics of vertical processes that extend across different cortical depths12.
Addressing these limitations, the present study outlines an innovative surgical procedure that integrates head plate fixation, microprism, and miniscope to create an imaging modality with multilayer and multimodal capabilities. The microprism allows the observation of the vertical processing along the cortical column13,14,15,16, which is critical in understanding how information is processed and transformed as it moves through different layers of the cortex and how the vertical processing is altered during plastic changes. Moreover, it permits imaging of the same neural populations in a head-fixed paradigm and in a freely moving setting, encompassing the versatile experimental settings17,18,19: for example, head-fixation is often required for well-controlled paradigms like sensory perception assessment and stable recordings under 2-photon paradigm, while freely moving offers a more natural, flexible environment for behavioral studies. Therefore, the ability to conduct a direct comparison in both modes is crucial to furthering our understanding of the microcircuits that enable flexible, functional responses.
In essence, the integration of head plate fixation, microprism, and miniscope in fluorescence imaging offers a promising platform for probing the intricacies of the brain&#39;s structure and functionality. Researchers can sample identified cell populations across various depths spanning all cortical layers, directly compare their responses in both well-controlled and natural paradigms, and monitor their long-term alterations over months20. This approach offers valuable insight into how these neural populations interact and change over time under different experimental conditions, providing a window into the dynamic nature of neural circuits.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
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			<td>0.9% Sodium Chloride solution for infusion (Vetivex 11) 250ml</td>
			<td>Dechra</td>
			<td>20091607</td>
			<td>Saline for hydration and drug reconsitution</td>
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		<tr>
			<td>18004-1 Trephine 1.8mm diameter bur</td>
			<td>FST</td>
			<td>18004-18</td>
			<td>Drill bit</td>
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		<tr>
			<td>1ml syringe</td>
			<td>Terumo</td>
			<td>MDSS01SE</td>
			<td>1ml syringe</td>
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		<tr>
			<td>23G x 5/8 inch 6% LUER needle</td>
			<td>Terumo</td>
			<td>NN-2316R</td>
			<td>23G needle</td>
		</tr>
		<tr>
			<td>71000 Automated stereotaxic apparatus w/ built-in software</td>
			<td>RWD</td>
			<td>-</td>
			<td>RWD</td>
		</tr>
		<tr>
			<td>Absorbable Haemostatic Gelatin Sponge (10x10x10mm)</td>
			<td>Surgispon</td>
			<td>SSP-101010</td>
			<td>gel-foam</td>
		</tr>
		<tr>
			<td>Alcohol pads 70% isopropyl alcohol</td>
			<td>Braun</td>
			<td>9160612</td>
			<td>Alcohol pads</td>
		</tr>
		<tr>
			<td>Aluminium foil</td>
			<td>Any retailer</td>
			<td>-</td>
			<td>Foil to cover eyes during surgery</td>
		</tr>
		<tr>
			<td>Articifical Cerebrospinal Fluid&#160;</td>
			<td>Tocris Bioscience a Bio-Techne Brand</td>
			<td>3525/25ML</td>
			<td>ACSF</td>
		</tr>
		<tr>
			<td>Automated microinjection pump</td>
			<td>WPI</td>
			<td>8091</td>
			<td></td>
		</tr>
		<tr>
			<td>Betadine solution (10% iodinated Povidone) 500ml</td>
			<td>Videne/Ecolab</td>
			<td>3030440</td>
			<td>Betadine</td>
		</tr>
		<tr>
			<td>Bruker Ultime 2Pplus (customised)</td>
			<td>Bruker</td>
			<td>-</td>
			<td>Two-photon imaging system&#160;</td>
		</tr>
		<tr>
			<td>Cardiff Aldasorber</td>
			<td>Vet-Tech</td>
			<td>AN006</td>
			<td>Anaesthesia absorber</td>
		</tr>
		<tr>
			<td>CFI S Plan Fluor ELWD ADM 20XC</td>
			<td>Nikon</td>
			<td>MRH48230</td>
			<td>20x objective lens</td>
		</tr>
		<tr>
			<td>Compact Anaesthesia system - single gas - isoflurane K/F, with oxygen concentrator model: ZY-5AC and scavenging unit</td>
			<td>Vet-Tech</td>
			<td>AN001</td>
			<td>Compact anaesthesia system&#160;</td>
		</tr>
		<tr>
			<td>Contec Prochlor&#160;</td>
			<td>Aston Pharma</td>
			<td>AP2111L1</td>
			<td>Disinfectant (hypochlorous acid)</td>
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		<tr>
			<td>Dexamethasone Sodium Phosphate Injection, USP, 4mg/ml, NDC: 0641-6145-25</td>
			<td>Hikma</td>
			<td>Covetrus:70789</td>
			<td>Dexamethasone</td>
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		<tr>
			<td>Dissecting Knife, cutting edge 4mm, thickness 0.5mm, stainless steel</td>
			<td>Fine Science Tools</td>
			<td>10055-12</td>
			<td>Knife for incisino of cortex</td>
		</tr>
		<tr>
			<td>Dual-Sided, Non-Puncture Mouse &#38; Neonatal Rat Ear Bars</td>
			<td>Stoelting</td>
			<td>51649</td>
			<td>Ear bar</td>
		</tr>
		<tr>
			<td>Dummy microscope</td>
			<td>Inscopix</td>
			<td>Dummy microscope</td>
			<td>To help with implantation</td>
		</tr>
		<tr>
			<td>Ethanol (100%)&#160;</td>
			<td>VWR</td>
			<td>40-1712-25</td>
			<td>Used to make 70% ethanol&#160;</td>
		</tr>
		<tr>
			<td>Fisherbrand&#160;Nitrile Indigo Disposable Gloves PPE Cat III</td>
			<td>FischerScientific</td>
			<td>17182182</td>
			<td>Gloves</td>
		</tr>
		<tr>
			<td>Homeothermic Monitor 50-7222-F</td>
			<td>Harvard Apparatus</td>
			<td>50-7222-F</td>
			<td>Homeothermic monitoring system/heating pad</td>
		</tr>
		<tr>
			<td>Image processing software</td>
			<td>ImageJ</td>
			<td>-</td>
			<td>Image processing software</td>
		</tr>
		<tr>
			<td>Inscopix Data Processing Software (IDPS)</td>
			<td>Inscopix</td>
			<td>-</td>
			<td>One-photon calcium imaging processing software</td>
		</tr>
		<tr>
			<td>Insight Duals-232, S/N 2043</td>
			<td>InSight</td>
			<td>Insight Spectra X3</td>
			<td>Two-photon imaging laser</td>
		</tr>
		<tr>
			<td>IsoFlo 250ml 100% w/w inhalation</td>
			<td>Zoetis</td>
			<td>WM 42058/4195</td>
			<td>Isoflurane</td>
		</tr>
		<tr>
			<td>Kwik-Sil Low Toxicity Silicone Adhesive</td>
			<td>World Precision Intruments (WPI)</td>
			<td>KWIK-SIL</td>
			<td>Silicone adhesive</td>
		</tr>
		<tr>
			<td>MICROMOT mains adapter NG 2/S, w/ Drill unit 60/E</td>
			<td>PROXXON</td>
			<td>NO 28 515</td>
			<td>Handheld drill</td>
		</tr>
		<tr>
			<td>nVoke Integrated Imaging and Optogenetics System package</td>
			<td>Inscopix</td>
			<td>-</td>
			<td>One-photon Imaging system and software</td>
		</tr>
		<tr>
			<td>ProView Implant Kit</td>
			<td>Inscopix</td>
			<td>ProView Implant Kit</td>
			<td>Dummy microscope, stereotaxic arm and attachment&#160;</td>
		</tr>
		<tr>
			<td>ProView Prism Probe</td>
			<td>Inscopix</td>
			<td>1050-002203</td>
			<td>Microprism lens</td>
		</tr>
		<tr>
			<td>Rimadyl (50mg/ml)</td>
			<td>Zoetis</td>
			<td>VM 42058/4123</td>
			<td>Carprofen&#160;</td>
		</tr>
		<tr>
			<td>Stereotaxis Microscope on Articulated arm with table clamp</td>
			<td>WPI</td>
			<td>PZMTIII-AAC&#160;</td>
			<td>Microscope</td>
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		<tr>
			<td>Super-Bond Universal kit, SUN Medical</td>
			<td>Prestige-Dental</td>
			<td>K058E</td>
			<td>Adhesive cement</td>
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		<tr>
			<td>Two-photon calcium image software</td>
			<td>Suite2P</td>
			<td>-</td>
			<td>Two-photon calcium imaging processing software</td>
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			<td>Vapouriser</td>
			<td>Vet-Tech</td>
			<td>-</td>
			<td>Isoflurane vapouriser</td>
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			<td>Xailin Lubricating Eye Ointment 5g</td>
			<td>Xailin-Night</td>
			<td>MLG/28/1551</td>
			<td>Ophthalmic ointment&#160;</td>
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long-term imaging of identified neural populations using microprisms in freely moving and head-fixed animals

With the advancement of multi-photon microscopy and molecular technologies, fluorescence imaging is rapidly growing to become a powerful approach for studying the structure, function, and plasticity of living brain tissues. In comparison to conventional electrophysiology, fluorescence microscopy can capture the neural activity as well as the morphology of the cells, enabling long-term recordings of the identified neuron populations at single-cell or subcellular resolution. However, high-resolution imaging typically requires a stable, head-fixed setup that restricts the movement of the animal, and the preparation of a flat surface of transparent glass allows visualization of neurons at one or more horizontal planes but is limited in studying the vertical processes running across different depths. Here, we describe a procedure to combine a head plate fixation and a microprism that gives multilayer and multimodal imaging. This surgical preparation not only gives access to the entire column of the mouse visual cortex but allows two-photon imaging in a head-fixed position and one-photon imaging in a freely moving paradigm. Using this approach, one can sample identified cell populations across different cortical layers, register their responses under head-fixed and freely moving states, and track the long-term changes over months. Thus, this method provides a comprehensive assay of the microcircuits, enabling direct comparison of neural activities evoked by well-controlled stimuli and under a natural behavioral paradigm.

The method of conducting chronic multilayer in vivo calcium imaging of the same neuronal population over a period of several weeks, using both one- and two-photon imaging modalities, under freely moving and head-fixed conditions has been shown. Here, the ability to identify matching neuronal populations under one-photon imaging while the animal explored an open arena in the dark has been demonstrated (Figure 7A). Calcium traces were extracted from the identified neurons and z-scored...

Watch this Scientific Journal Video about Long-Term Imaging of Identified Neural Populations using Microprisms in Freely Moving and Head-Fixed Animals at JoVE.com

Author Spotlight: Comparative Imaging of Neural Activity in Awake and Freely Moving States

When integrated with a head-plate and an optical design compatible with both single- and two-photon microscopes, the microprism lens presents a significant advantage in measuring neural responses in a vertical column under diverse conditions, including well-controlled experiments in head-fixed states or natural behavioral tasks in freely moving animals.

Long-Term Imaging of Identified Neural Populations using Microprisms in Freely Moving and Head-Fixed Animals

With the advancement of multi-photon microscopy and molecular technologies, fluorescence imaging is rapidly growing to become a powerful approach for ...

long-term-imaging-identified-neural-populations-using-microprisms

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Neuroscience

866 Views.  University College London. When integrated with a head-plate and an optical design compatible with both single- and two-photon microscopes, the microprism lens presents a significant advantage in measuring neural responses in a vertical column under diverse conditions, including well-controlled experiments in head-fixed states or natural behavioral tasks in freely moving animals.

Video: Author Spotlight: Comparative Imaging of Neural Activity in Awake and Freely Moving States

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.  ...

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 ...

Design and Assembly of an Ultra-light Motorized Microdrive for Chronic Neural Recordings in Small Animals

The ability to chronically record from populations of neurons in freely behaving animals has proven an invaluable tool for dissecting the function of neural circuits underlying a variety of natural behaviors, including navigation1 , decision making 2,3, and the generation of complex motor sequences4,5,6. Advances in precision machining has allowed for the fabrication of light-weight devices suitable for chronic recordings in small animals, such as mice and songbirds. The ability to adjust the electrode position with small remotely controlled motors has further increased the recording yield in various behavioral contexts by reducing animal handling.6,7
 Here we describe a protocol to build an ultra-light motorized microdrive for long-term chronic recordings in small animals. Our design evolved from an earlier published version7, and has been adapted for ease-of use and cost-effectiveness to be more practical and accessible to a wide array of researchers. This proven design 8,9,10,11 allows for fine, remote positioning of electrodes over a range of ~ 5 mm and weighs less than 750 mg when fully assembled. We present the complete protocol for how to build and assemble these drives, including 3D CAD drawings for all custom microdrive components.

The design, fabrication and assembly of an ultra-light motorized microdrive is described. The device provides a cost-effective and easy-to-use solution for chronic recordings of single units in small behaving animals.

The ability to chronically record from populations of neurons in freely behaving animals has proven an invaluable tool for dissecting the function of ...

Long-term Behavioral Tracking of Freely Swimming Weakly Electric Fish

Long-term behavioral tracking can capture and quantify natural animal behaviors, including those occurring infrequently. Behaviors such as exploration and social interactions can be best studied by observing unrestrained, freely behaving animals. Weakly electric fish (WEF) display readily observable exploratory and social behaviors by emitting electric organ discharge (EOD). Here, we describe three effective techniques to synchronously measure the EOD, body position, and posture of a free-swimming WEF for an extended period of time. First, we describe the construction of an experimental tank inside of an isolation chamber designed to block external sources of sensory stimuli such as light, sound, and vibration. The aquarium was partitioned to accommodate four test specimens, and automated gates remotely control the animals&#39; access to the central arena. Second, we describe a precise and reliable real-time EOD timing measurement method from freely swimming WEF. Signal distortions caused by the animal&#39;s body movements are corrected by spatial averaging and temporal processing stages. Third, we describe an underwater near-infrared imaging setup to observe unperturbed nocturnal animal behaviors. Infrared light pulses were used to synchronize the timing between the video and the physiological signal over a long recording duration. Our automated tracking software measures the animal&#39;s body position and posture reliably in an aquatic scene. In combination, these techniques enable long term observation of spontaneous behavior of freely swimming weakly electric fish in a reliable and precise manner. We believe our method can be similarly applied to the study of other aquatic animals by relating their physiological signals with exploratory or social behaviors.

We describe a set of techniques for studying spontaneous behavior of freely swimming weakly electric fish over an extended period of time, by synchronously measuring the animal&#39;s electric organ discharge timing, body position and posture both accurately and reliably in a specially designed aquarium tank inside a sensory isolation chamber.

Long-term behavioral tracking can capture and quantify natural animal behaviors, including those occurring infrequently. Behaviors such as exploration and ...

Long-term Time Lapse Imaging of Mouse Cochlear Explants

Here we present a method for long-term time-lapse imaging of live embryonic mouse cochlear explants. The developmental program responsible for building the highly ordered, complex structure of the mammalian cochlea proceeds for around ten days. In order to study changes in gene expression over this period and their response to pharmaceutical or genetic manipulation, long-term imaging is necessary. Previously, live imaging has typically been limited by the viability of explanted tissue in a humidified chamber atop a standard microscope. Difficulty in maintaining optimal conditions for culture growth with regard to humidity and temperature has placed limits on the length of imaging experiments. A microscope integrated into a modified tissue culture incubator provides an excellent environment for long term-live imaging. In this method we demonstrate how to establish embryonic mouse cochlear explants and how to use an incubator microscope to conduct time lapse imaging using both bright field and fluorescent microscopy to examine the behavior of a typical embryonic day (E) 13 cochlear explant and Sox2, a marker of the prosensory cells of the cochlea, over 5 days.

Live imaging of the embryonic mammalian cochlea is challenging because the developmental processes at hand operate on a temporal gradient over ten days. Here we present a method for culturing and then imaging embryonic cochlear explant tissue taken from a fluorescent reporter mouse over five days.

Here we present a method for long-term time-lapse imaging of live embryonic mouse cochlear explants. The developmental program responsible for building ...

Agarose Microchambers for Long-term Calcium Imaging of Caenorhabditis elegans

Behavior is controlled by the nervous system. Calcium imaging is a straightforward method in the transparent nematode Caenorhabditis elegans to measure the activity of neurons during various behaviors. To correlate neural activity with behavior, the animal should not be immobilized but should be able to move. Many behavioral changes occur during long time scales and require recording over many hours of behavior. This also makes it necessary to culture the worms in the presence of food. How can worms be cultured and their neural activity imaged over long time scales? Agarose Microchamber Imaging (AMI) was previously developed to culture and observe small larvae and has now been adapted to study all life stages from early L1 until the adult stage of C. elegans. AMI can be performed on various life stages of C. elegans. Long-term calcium imaging is achieved without immobilizing the animals by using short externally triggered exposures combined with an electron multiplying charge-coupled device (EMCCD) camera recording. Zooming out or scanning can scale up this method to image up to 40 worms in parallel. Thus, a method is described to image behavior and neural activity over long time scales in all life stages of C. elegans.

Agarose Microchambers for Long-term Calcium Imaging of Caenorhabditis elegans

Imaging behavior and neural activity over long time scales without immobilization of the animal is a prerequisite to understand behavior. Agarose microfluidic chambers imaging (AMI) can be used to image neural activity and behavior for all life stages of Caenorhabditis elegans.

Behavior is controlled by the nervous system. Calcium imaging is a straightforward method in the transparent nematode Caenorhabditis elegans to measure ...

Recording EEG in Freely Moving Neonatal Rats Using a Novel Method

EEG is a useful method to detect electrical activity in the brain. Moreover, it is a widely used diagnostic tool for various neurological conditions, such as epilepsy and neurodegenerative disorders. However, it is technically difficult to obtain EEG recordings in neonates as it requires specialized handling and great care. Here, we present a novel method to record EEG in neonatal rat pups (P8-P15). We designed a simple and reliable electrode using computer pin loci; it can be easily implanted into the skull of a rat pup to record high-quality EEG signals in the normal and epileptic brain. Pups were given an intraperitoneal (i.p.) injection of the neurotoxin kainic acid (KA) to induce epileptic seizures. The surgical implantation performed in this procedure is less expensive than other EEG procedures for neonates. This method allows one to record high-quality and stable EEG signals for more than 1 week. Furthermore, this procedure can also be applied to adult rats and mice to study epilepsy or other neurological disorders.

Here, we introduce a novel technique designed to record electroencephalography (EEG) in freely moving neonatal epileptic pups and describe its procedures, features, and applications. This method allows one to record EEG for more than 1 week.

EEG is a useful method to detect electrical activity in the brain. Moreover, it is a widely used diagnostic tool for various neurological conditions, such ...

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

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

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

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

Noninvasive EEG Recordings from Freely Moving Piglets

The method allows the recording of high-quality electroencephalograms (EEGs) from freely moving piglets directly in the pigpen. We use a one-channel telemetric electroencephalography system in combination with standard self-adhesive hydrogel electrodes. The piglets are calmed down without the use of sedatives. After their release into the pigpen, the piglets behave normally&#8212;they drink and sleep in the same cycle as their siblings. Their sleep phases are used for the EEG recordings.

Here, we present a protocol to record telemetric electroencephalograms (EEGs) from freely moving piglets directly in the pigpen without the use of a sedative, making it possible to record typical EEG patterns during non-REM sleep, like spindle bursts.

The method allows the recording of high-quality electroencephalograms (EEGs) from freely moving piglets directly in the pigpen. We use a one-channel ...

Microdialysis of Excitatory Amino Acids During EEG Recordings in Freely Moving Rats

Microdialysis is a well-established neuroscience technique that correlates the changes of neurologically active substances diffusing into the brain interstitial space with the behavior and/or with the specific outcome of a pathology (e.g., seizures for epilepsy). When studying epilepsy, the microdialysis technique is often combined with short-term or even long-term video-electroencephalography (EEG) monitoring to assess spontaneous seizure frequency, severity, progression and clustering. The combined microdialysis-EEG is based on the use of several methods and instruments. Here, we performed in vivo microdialysis and continuous video-EEG recording to monitor glutamate and aspartate outflow over time, in different phases of the natural history of epilepsy in a rat model. This combined approach allows the pairing of changes in the neurotransmitter release with specific stages of the disease development and progression. The amino acid concentration in the dialysate was determined by liquid chromatography. Here, we describe the methods and outline the principal precautionary measures one should take during in vivo microdialysis-EEG, with particular attention to the stereotaxic surgery, basal and high potassium stimulation during microdialysis, depth electrode EEG recording and high-performance liquid chromatography analysis of aspartate and glutamate in the dialysate. This approach may be adapted to test a variety of drug or disease induced changes of the physiological concentrations of aspartate and glutamate in the brain. Depending on the availability of an appropriate analytical assay, it may be further used to test different soluble molecules when employing EEG recording at the same time.

Here, we describe a method for in vivo microdialysis to analyze aspartate and glutamate release in the ventral hippocampus of epileptic and non-epileptic rats, in combination with EEG recordings. Extracellular concentrations of aspartate and glutamate may be correlated with the different phases of the disease.

Microdialysis is a well-established neuroscience technique that correlates the changes of neurologically active substances diffusing into the brain ...