The authors would like to thank Dr. Christina Ginkel (German Center for Neurodegenerative Diseases, DZNE), Dr. Michaela M&#246;hring (DZNE) and Dr. Robert Stark (DZNE) for assistance in animal breeding and animal health care. This work was financially supported by the Federal Institute for Drugs and Medical Devices (Bundesinstitut f&#252;r Arzneimittel und Medizinprodukte, BfArM) Bonn, Germany.

The authors have nothing to disclose.

Implantable EEG radiotelemetry is of central relevance as it is a non-restraining technique allowing experimental animals to perform their full repertoire of behavior1,3. This is of major interest as the telemetric approach enables not only spontaneous EEG recordings but also recordings under cognitive tasks and circadian analytical setups, such as T-maze, radial maze, water maze, sleep deprivation tasks or whenever an EEG recording is necessary or helpful during complex cognitive or motor activity.
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Radiotelemetry is a most valuable methodological approach for measuring a variety of behavioral and physiological parameters in conscious, unrestrained animals of various sizes, particularly in the context of EEG, ECG, EMG, blood pressure, body core temperature or activity measurements 1-7. Theoretically, any species can be analyzed using implantable EEG radiotelemetry from laboratory rodents such as mice and rats to cats, dogs, pigs and primates 3,8. Even fish, reptiles and amphibians are subject to radiotelemetric investigation 9. Over the last two decades, implantable EEG radiotelemetry has proven to be valuable in the characterization of various transgenic animal models of human diseases, such as epilepsies, sleep disorders, neurodegenerative and neuropsychiatric disorders 7,10-12. In the past, numerous methodological approaches collecting physiological data including biopotentials from mice and rats have been described. Worn in jacket recorder systems, physical restraint methods, non-implanted radiotransmitters and tethered systems have received the main attention in the past 13,14. Nowadays, various systems for radiotelemetric implantation are commercially available. However, a literature screen also revealed 29 publications that describe the development of self-made radiotelemetric systems 15-40. Whereas home-made systems are likely to be less expensive and more user adapted, commercially available systems are straight forward, relatively easy to install and can be setup quickly.
Implantable EEG radiotelemetry has a number of advantages compared to competing techniques such as physical restraint methods, worn in jacket systems or tethered approaches. The latter are restraining by definition, i.e., the animal is unable to move or its normal behavior is impaired. It might even be necessary to anesthetize the animal for acquisition of reliable data. Modern tethered systems however are likely to be less restraining, but this needs to be scientifically validated. Radiotelemetry on the other hand allows animals to exhibit their full repertoire of behavior without spatiotemporal restrictions and thus, is thought to be superior to restraining approaches and be more predictive of the results that could be acquired in humans 1,3. It is known for quite a while that restraining approaches can dramatically alter fundamental physiological parameters, e.g., food intake, body core temperature, blood pressure and heart rate and physical activity for example 3. Tethered systems represent one still widely used classical restraining approach 13,14. The electrodes which are either epidural or deep electrodes are generally connected to a miniature socket which is anchored to the skull. The socket itself is exposed for attachment of a cable that allows relatively free movement of the animal. Although nowadays tethered systems have become extremely filigree and highly flexible, one of its major disadvantages is, that it is still semi-restraining. Besides, there might be a risk of infection at the electrode implantation site as the animals tend to manipulate any external devices originating from their body (head). Although wireless radiotelemetry technology in various species has already been described in the late 60s and has thus existed for decades, it has only recently become affordable, reliable, and relatively easy-to-use 10,41,42, particularly in small laboratory rodents such as mice and rats. Small, miniature implantable EEG transmitters are now commercially available and can be implanted in mice greater than 20 g (~10 weeks). Thus, the electrophysiological characterization of transgenic mouse models in particular has become a predominant field of application of implantable EEG radiotelemetry these days. Animal size is no longer an absolute experimental restriction whereas the life-span of the transmitters&#39; battery indeed is. Despite its limited life-time, implantable transmitter systems are capable of minimizing most disadvantages related to potential recording-associated stress by restraining systems. Rodents can present their complete armamentarium of physiological behavior including resting, locomotor activity (exploration) and sleep (REM, slow-wave sleep) 43,44. Importantly, implantable radiotelemetry can strongly reduce animal use 3. Currently, there is an intense discussion on how to limit the number of experimental animals in science and reduce their suffering. Clearly, animal experimentation and animal models of human and animal diseases are essential for our understanding of the bottom-line pathophysiology and subsequent progress in therapy. Furthermore, animal experiments are critical in drug research and development. They do substantially contribute to preclinical/toxicological studies in drug licensing thus committing to both human and animal care. It&#39;s noteworthy, that currently no alternatives are yet available to animal research to understand the complex pathophysiological mechanisms which would be otherwise impossible to be elicited. At the same time, the 3R, i.e., replacement, reduction and refinement strategy in the EU and the USA strongly encourages research into complementary and alternative methods. Radiotelemetry is an important example of a successful 3R strategy as it can reduce the number of experimental animals and their suffering compared to other techniques.
Here we provide a detailed and contiguous step-by-step approach to perform a subcutaneous pouch implantation of a radiofrequency transmitter in both mice and rats. This first sequence is followed by a description of stereotaxic epidural and deep intracerebral EEG electrode positioning. Special attention is paid to housing conditions, anesthesia, peri- and postoperative pain management and possible anti-infective treatment. The focus is on the computerized 3D stereotaxic approach to reliably target epidural and deep intracerebral structures. We also comment on frequent experimental pitfalls in EEG electrode implantation and strategies for reduction of trauma and optimization of pain management during postoperative recovery. Finally, examples of surface and deep EEG recordings are presented.

<table><tbody><tr><td>Carprofen (Rimadyl VET - InjektionA2:D43sl&amp;ouml;sung)</td><td>Pfizer</td><td>PZN 0110208</td><td>20 ml</td></tr><tr><td>Binocular surgical magnification microscope&amp;nbsp;</td><td>Zeiss Stemi 2000</td><td>0000001003877, 4355400000000, 0000001063306, 4170530000000, 4170959255000, 4551820000000, 4170959040000, 4170959050000</td><td></td></tr><tr><td>Bulldog serrefine</td><td>F.S.T.</td><td>18051-28</td><td>28 mm</td></tr><tr><td>Cages (Macrolon)</td><td>Techniplast</td><td>1264C, 1290D</td><td></td></tr><tr><td>Cold light source</td><td>Schott KL2500 LCD</td><td>9.705&amp;nbsp;202</td><td>ordered at Th.Geyer</td></tr><tr><td>Cotton tip applicators (sterile)</td><td>Carl Roth&amp;nbsp;</td><td>EH12.1</td><td></td></tr><tr><td>Dexpanthenole (Bepanthen Wund- und Heilsalbe)</td><td>Bayer</td><td>PZN: 1578818</td><td></td></tr><tr><td>Drapes (sterile)</td><td>Hartmann</td><td>PZN 0366787</td><td></td></tr><tr><td>70% ethanol</td><td>Carl Roth&amp;nbsp;</td><td>9065.5</td><td></td></tr><tr><td>0.3%/3% hydrogene peroxide solution</td><td>Sigma</td><td>95321</td><td>30% stock solution&amp;nbsp;</td></tr><tr><td>Gloves (sterile)</td><td>Unigloves</td><td>1570</td><td></td></tr><tr><td>Dental glas ionomer cement</td><td>KentDental /NORDENTA</td><td>957 321</td><td></td></tr><tr><td>2% glutaraldehyde solution</td><td>Sigma</td><td>G6257</td><td></td></tr><tr><td>Graefe Forceps-curved, serrated</td><td>F.S.T.</td><td>11052-10</td><td></td></tr><tr><td>Halsey Micro Needle Holder-Tungsten Carbide</td><td>F.S.T.</td><td>12500-12</td><td>12.5 cm</td></tr><tr><td>Heat-based surgical instrument sterilizer</td><td>F.S.T.</td><td>18000-50</td><td></td></tr><tr><td>Heating pad</td><td>AEG HK5510</td><td>520010</td><td>ordered at myToolStore</td></tr><tr><td>High-speed dental drill</td><td>Adeor</td><td>SI-1708</td><td></td></tr><tr><td>Iris scissors extra thin&amp;nbsp;</td><td>F.S.T.</td><td>14058-09</td><td>9 cm</td></tr><tr><td>Inhalation narcotic system (isoflurane)</td><td>Harvard Apparatus GmbH</td><td>34-1352, 10-1340, 34-0422, 34-1041, 34-0401, 34-1067, 72-3044, 34-0426, 34-0387, 34-0415, 69-0230</td><td></td></tr><tr><td>Isoflurane</td><td>Baxter 250 ml</td><td>PZN 6497131</td><td></td></tr><tr><td>Ketamine</td><td>Pfizer</td><td>PZN 07506004</td><td></td></tr><tr><td>Lactated Ringer&amp;rsquo;s solution (sterile)</td><td>Braun</td><td>L7502</td><td></td></tr><tr><td>Lexar-Baby Scissors-straight, 10 cm</td><td>F.S.T.</td><td>14078-10</td><td>10 cm</td></tr><tr><td>Nissl staining solution</td><td>Armin Baack</td><td>BAA31712159</td><td></td></tr><tr><td>Non-absorbable suture material 5-0/6-0 (sterile)</td><td>SABANA (Sabafil)</td><td>N-63123-45</td><td></td></tr><tr><td></td><td>Covidien (Sofsilk)</td><td>S1172, S1173</td><td></td></tr><tr><td>Halsey Needle Holder</td><td>F.S.T.</td><td>12001-13</td><td>13 cm</td></tr><tr><td>Pads (sterile)</td><td>ReWa Krankenhausbedarf</td><td>2003/01</td><td></td></tr><tr><td>0.9% saline (NaCl, sterile)</td><td>Braun</td><td>PZN:8609255</td><td></td></tr><tr><td>Scalpel blades with handle (sterile)</td><td>propraxis</td><td>2029/10</td><td></td></tr><tr><td>Standard Pattern Forceps</td><td>F.S.T.</td><td>11000-12, 11000-14</td><td>12 cm and 14.5 cm length</td></tr><tr><td>Steel and tungsten electrodes parylene coated&amp;nbsp;</td><td>FHC Inc., USA)</td><td>UEWLGESEANND</td><td></td></tr><tr><td>Stereotaxic frame</td><td>Neurostar</td><td>51730M</td><td>ordered at Stoelting</td></tr><tr><td>(Stereo Drive-New Motorized Stereotaxic)</td><td></td><td></td><td></td></tr><tr><td>Tapes (sterile)</td><td>BSN medical GmbH &amp;amp; Co. KG</td><td>626225</td><td></td></tr><tr><td>TA10ETA-F20&amp;nbsp;</td><td>DSI</td><td>270-0042-001X</td><td>Radiofrequency transmitter 3.9 g,&amp;nbsp;&lt;br/&gt; 3.9 g, 1.9 ml, input voltage range &amp;plusmn; 2.5 mV,&lt;br/&gt; channel bandwidth (B) 1 - 200 Hz,&amp;nbsp;&lt;br/&gt; nominal sampling rate (f) 1,000 Hz (f = 5B)&lt;br/&gt; temperature operating range 34 - 41 &amp;deg;C&lt;br/&gt; warranted battery life 4 months</td></tr><tr><td>TL11M2-F20EET&amp;nbsp;</td><td>DSI</td><td>270-0124-001X</td><td>Radiofrequency transmitter&amp;nbsp;&lt;br/&gt; 3.9 g, 1.9 ml, input voltage range &amp;plusmn; 1.25 mV,&lt;br/&gt; channel bandwidth (B) 1 - 50 Hz,&amp;nbsp;&lt;br/&gt; nominal sampling rate (f) 250 Hz (f = 5B)&lt;br/&gt; temperature operating range 34 - 41 &amp;deg;C&lt;br/&gt; warranted battery life 1.5 months</td></tr><tr><td>Tissue Forceps- 1x2 Teeth 12 cm</td><td>F.S.T.</td><td>11021-12</td><td>12 cm length</td></tr><tr><td>Tungsten carbide iris scissors</td><td>F.S.T.</td><td>14558-11</td><td>11.5 cm</td></tr><tr><td>Vibroslicer 5000 MZ</td><td>Electron Microscopy Sciences</td><td>5000-005</td><td></td></tr><tr><td>Xylazine (Rompun)</td><td>Bayer</td><td>PZN: 1320422</td><td></td></tr></tbody></table>

non-restraining eeg radiotelemetry: epidural and deep intracerebral stereotaxic eeg electrode placement

Implantable EEG radiotelemetry is of central relevance in the neurological characterization of transgenic mouse models of neuropsychiatric and neurodegenerative diseases as well as epilepsies. This powerful technique does not only provide valuable insights into the underlying pathophysiological mechanisms, i.e., the etiopathogenesis of CNS related diseases, it also facilitates the development of new translational, i.e., therapeutic approaches. Whereas competing techniques that make use of recorder systems used in jackets or tethered systems suffer from their unphysiological restraining to semi-restraining character, radiotelemetric EEG recordings overcome these disadvantages. Technically, implantable EEG radiotelemetry allows for precise and highly sensitive measurement of epidural and deep, intracerebral EEGs under various physiological and pathophysiological conditions. First, we present a detailed protocol of a straight forward, successful, quick and efficient technique for epidural (surface) EEG recordings resulting in high-quality electrocorticograms. Second, we demonstrate how to implant deep, intracerebral EEG electrodes, e.g., in the hippocampus (electrohippocampogram). For both approaches, a computerized 3D stereotaxic electrode implantation system is used. The radiofrequency transmitter itself is implanted into a subcutaneous pouch in both mice and rats. Special attention also has to be paid to pre-, peri- and postoperative treatment of the experimental animals. Preoperative preparation of mice and rats, suitable anesthesia as well as postoperative treatment and pain management are described in detail.

This section illustrates examples obtained from surface and deep, intracerebral EEG recordings. Initially it should be stated that baseline recordings under physiological conditions are mandatory prior to subsequent recordings following e.g., pharmacological treatment. Such baseline recordings may provide valuable information about functional interdependence of brain rhythmicity with different behavioral states or sleep / circadian rhythmicity. Here, we show examples of recorded ...

Watch this Scientific Journal Video about Non-restraining EEG Radiotelemetry: Epidural and Deep Intracerebral Stereotaxic EEG Electrode Placement at JoVE.com

Non-restraining EEG Radiotelemetry: Epidural and Deep Intracerebral Stereotaxic EEG Electrode Placement

Non-restraining EEG radiotelemetry is a valuable methodological approach to record in vivo long-term electroencephalograms from freely moving rodents. This detailed protocol describes stereotaxic epidural and deep intracerebral electrode placement in different brain regions in order to obtain reliable recordings of CNS rhythmicity and CNS related behavioral stages.

Implantable EEG radiotelemetry is of central relevance in the neurological characterization of transgenic mouse models of neuropsychiatric and ...

non-restraining-eeg-radiotelemetry-epidural-deep-intracerebral

Research

JoVE Journal

Neuroscience

19.1K Views.  Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM).  Non-straatverbod EEG radiotelemetrie is een waardevolle methodologische benadering om in vivo langdurige electroencephalograms opnemen van vrij bewegende knaagdieren. Deze gedetailleerde protocol beschrijft stereotaxische epidurale en diepe intracerebrale elektroden plaatsing in verschillende hersengebieden om betrouwbare opnames van CNS ritmiek en CNS gedragsstoornissen stadia te verkrijgen. 

Video: Non-restraining EEG Radiotelemetry: Epidural and Deep Intracerebral Stereotaxic EEG Electrode Placement

Performing Behavioral Tasks in Subjects with Intracranial Electrodes

Patients having stereo-electroencephalography (SEEG) electrode, subdural grid or depth electrode implants have a multitude of electrodes implanted in different areas of their brain for the localization of their seizure focus and eloquent areas. After implantation, the patient must remain in the hospital until the pathological area of brain is found and possibly resected. During this time, these patients offer a unique opportunity to the research community because any number of behavioral paradigms can be performed to uncover the neural correlates that guide behavior. Here we present a method for recording brain activity from intracranial implants as subjects perform a behavioral task designed to assess decision-making and reward encoding. All electrophysiological data from the intracranial electrodes are recorded during the behavioral task, allowing for the examination of the many brain areas involved in a single function at time scales relevant to behavior. Moreover, and unlike animal studies, human patients can learn a wide variety of behavioral tasks quickly, allowing for the ability to perform more than one task in the same subject or for performing controls. Despite the many advantages of this technique for understanding human brain function, there are also methodological limitations that we discuss, including environmental factors, analgesic effects, time constraints and recordings from diseased tissue. This method may be easily implemented by any institution that performs intracranial assessments; providing the opportunity to directly examine human brain function during behavior.

Patients implanted with intracranial electrodes provide a unique opportunity to record neurological data from multiple areas of the brain while the patient performs behavioral tasks. Here, we present a method of recording from implanted patients that can be reproducible at other institutions with access to this patient population.

Patients having stereo-electroencephalography (SEEG) electrode, subdural grid or depth electrode implants have a multitude of electrodes implanted in ...

Behavior

Use of a Wireless Video-EEG System to Monitor Epileptiform Discharges Following Lateral Fluid-Percussion Induced Traumatic Brain Injury

The lateral fluid percussion injury (FPI) model is well established and has been used to study TBI and post-traumatic epilepsy (PTE). However, considerable variability has been reported for the specific parameters used in different studies that have employed this model, making it difficult to harmonize and interpret the results between laboratories. For example, variability has been reported regarding the size and location of the craniectomy, how the Luer lock hub is placed relative to the craniectomy, the atmospheric pressure applied to the dura and the duration of the pressure pulse. Each of these parameters can impact injury severity, which directly correlates with the incidence of PTE. This has been manifested as a wide range of mortality rates, righting reflex times and incidence of convulsive seizures reported. Here we provide a detailed protocol for the method we have used to help facilitate harmonization between studies. We used FPI in combination with a wireless EEG telemetry system to continuously monitor for electrographic changes and detect seizure activity.&#160; FPI is induced by creating a 5 mm craniectomy over the left hemisphere, between the Bregma and Lambda and adjacent to the lateral ridge. A Luer lock hub is secured onto the skull over the craniectomy. This hub is connected to the FPI device, and a 20-millisecond pressure pulse is delivered directly to the intact dura through pressure tubing connected to the hub via a twist lock connector. Following recovery, rats are re-anesthetized to remove the hub. Five 0.5 mm, stainless steel EEG electrode screws are placed in contact with the dura through the skull and serve as four recording electrodes and one reference electrode. The electrode wires are collected into a pedestal connector which is secured into place with bone cement. Continuous video/EEG recordings are collected for up to 4 weeks post TBI.

Here we present a protocol to induce severe TBI with the lateral fluid percussion injury (FPI) model in adult, male Wistar rats. We also demonstrate the use of a wireless telemetry system to collect continuous video-EEG recordings and monitor for epileptiform discharges consistent with post-traumatic epileptogenesis.&#160;

The lateral fluid percussion injury (FPI) model is well established and has been used to study TBI and post-traumatic epilepsy (PTE). However, ...

Inducing Post-Traumatic Epilepsy in a Mouse Model of Repetitive Diffuse Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of acquired epilepsy. TBI can result in a focal or diffuse brain injury. Focal injury is a result of direct mechanical forces, sometimes penetrating through the cranium, creating a direct lesion in the brain tissue. These are visible during brain imaging as areas with contusion, laceration, and hemorrhage. Focal lesions induce neuronal death and glial scar formation and are present in 20%&minus;25% of all people who incur a TBI. However, in the majority of TBI cases, injury is caused by acceleration-deceleration forces and subsequent tissue shearing, resulting in nonfocal, diffuse damage. A subpopulation of TBI patients continues to develop post-traumatic epilepsy (PTE) after a latency period of months or years. Currently, it is impossible to predict which patients will develop PTE, and seizures in PTE patients are challenging to control, necessitating further research. Until recently, the field was limited to only two animal/rodent models with validated spontaneous post-traumatic seizures, both presenting with large focal lesions with massive tissue loss in the cortex and sometimes subcortical structures. In contrast to these approaches, it was determined that diffuse TBI induced using a modified weight drop model is sufficient to initiate development of spontaneous convulsive and non-convulsive seizures, even in the absence of focal lesions or tissue loss. Similar to human patients with acquired post-traumatic epilepsy, this model presents with a latency period after injury before seizure onset. In this protocol, the community will be provided with a new model of post-traumatic epilepsy, detailing how to induce diffuse non-lesional TBI followed by continuous long-term video-electroencephalographic animal monitoring over the course of several months. This protocol will detail animal handling, the weight drop procedure, the electrode placement for two acquisition systems, and the frequent challenges encountered during each of the steps of surgery, postoperative monitoring, and data acquisition.

This systematic protocol describes a new animal model of post-traumatic epilepsy after repetitive mild traumatic brain injury. The first part details steps for traumatic brain injury induction using a modified weight drop model. The second part provides instructions on the surgical approach for single- and multi-channel electroencephalographic data acquisition systems.

Traumatic brain injury (TBI) is a leading cause of acquired epilepsy. TBI can result in a focal or diffuse brain injury. Focal injury is a result of ...

Operative Technique and Nuances for the Stereoelectroencephalographic (SEEG) Methodology Utilizing a Robotic Stereotactic Guidance System

The SEEG methodology has gained favor in North America over the last decade as a means of localizing the epileptogenic zone (EZ) prior to epilepsy surgery. Recently, the application of a robotic stereotactic guidance system for implantation of SEEG electrodes has become more popular in many epilepsy centers. The technique for the use of the robot requires extreme precision in the pre-surgical planning phase and then the technique is streamlined during the operative portion of the methodology, as the robot and surgeon work in concert to implant the electrodes. Herein is detailed precise operative methodology of using the robot to guide implantation of SEEG electrodes. A major limitation of the procedure, namely its heavy reliance on the ability to register the patient to a preoperative volumetric magnetic resonance image (MRI), is also discussed. Overall, this procedure has been shown to have a low morbidity rate and an extremely low mortality rate. The use of a robotic stereotactic guidance system for the implantation of SEEG electrodes is an efficient, fast, safe, and accurate alternative to conventional manual implantation strategies.

Operative Technique and Nuances for the Stereoelectroencephalographic SEEG Methodology Utilizing a Robotic Stereotactic Guidance System

The SEEG methodology is simplified and made faster with a stereotactic robot. Careful attention must be paid to the registration of the preoperative volumetric MRI to the patient prior to use of the robot in the OR. The robot streamlines the procedure, leading to decreased operative times and accurate implantations.

The SEEG methodology has gained favor in North America over the last decade as a means of localizing the epileptogenic zone (EZ) prior to epilepsy ...

Investigating the Function of Deep Cortical and Subcortical Structures Using Stereotactic Electroencephalography: Lessons from the Anterior Cingulate Cortex

Stereotactic Electroencephalography (SEEG) is a technique used to localize seizure foci in patients with medically intractable epilepsy. This procedure involves the chronic placement of multiple depth electrodes into regions of the brain typically inaccessible via subdural grid electrode placement. SEEG thus provides a unique opportunity to investigate brain function. In this paper we demonstrate how SEEG can be used to investigate the role of the dorsal anterior cingulate cortex (dACC) in cognitive control. We include a description of the SEEG procedure, demonstrating the surgical placement of the electrodes. We describe the components and process required to record local field potential (LFP) data from consenting subjects while they are engaged in a behavioral task. In the example provided, subjects play a cognitive interference task, and we demonstrate how signals are recorded and analyzed from electrodes in the dorsal anterior cingulate cortex, an area intimately involved in decision-making. We conclude with further suggestions of ways in which this method can be used for investigating human cognitive processes.

Stereotactic Electroencephalography (SEEG) is an operative technique used in epilepsy surgery to help localize seizure foci. It also affords a unique opportunity to investigate brain function. Here we describe how SEEG can be used to investigate cognitive processes in human subjects.

Stereotactic Electroencephalography (SEEG) is a technique used to localize seizure foci in patients with medically intractable epilepsy. This procedure ...

Stereo-Electro-Encephalo-Graphy (SEEG) With Robotic Assistance in the Presurgical Evaluation of Medical Refractory Epilepsy: A Technical Note

SEEG is a method and technique which is used for accurate, invasive recording of seizure activity via three dimensional recordings. In epilepsy patients who are deemed appropriate candidates for invasive recordings, the decision to monitor is made between the subdural grids versus SEEG. Invasive neuromonitoring for epilepsy is pursued in patients with complex, medically refractory epilepsy. The goal of invasive monitoring is to offer resective surgery with the hope of allowing seizure freedom. SEEG&#39;s advantages include access to deep cortical structures, an ability to localize the epileptogenic zone (EZ) when subdural grids have failed to do so, and in patients with non-lesional extra-temporal epilepsies. In this manuscript, we present a succinct historical overview of the SEEG and report on our experience with frameless stereotaxy under robotic. An imperative step of SEEG insertion is planning the electrode trajectories. In order to most effectively record ictal activity via SEEG trajectories should be planned based upon a hypothesis of where the seizure activity originates the presumed epileptogenic zone (EZ). The EZ hypothesis is based on a standardized preoperative workup including video-EEG monitoring, MRI (magnetic resonance imaging), PET (positron emission tomography), ictal SPECT (Single-photon emission computed tomography), and neuropsychological assessment. Using a suspected EZ, SEEG electrodes can be placed minimally invasively yet maintain accuracy and precision. Clinical results showed the ability to localize the EZ in 78% of difficult to localize epileptic patients.1

Stereo-Electro-Encephalo-Graphy SEEG With Robotic Assistance in the Presurgical Evaluation of Medical Refractory Epilepsy: A Technical Note

Stereo-electroencephalography (SEEG) aids in localization of epileptogenic zones, however, remains relatively underutilized in the United States. The goal of this abstract is to provide a brief introduction to the technique of SEEG and further a detailed technique of using robotic assistance in the placement of SEEG electrodes.

SEEG is a method and technique which is used for accurate, invasive recording of seizure activity via three dimensional recordings. In epilepsy patients ...

Medicine

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

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

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

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

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

Subdural Soft Electrocorticography (ECoG) Array Implantation and Long-Term Cortical Recording in Minipigs

Neurological impairments and diseases can be diagnosed or treated using electrocorticography (ECoG) arrays. In drug-resistant epilepsy, these help delineate the epileptic region to resect. In long-term applications such as brain-computer interfaces, these epicortical electrodes are used to record the movement intention of the brain, to control the robotic limbs of paralyzed patients. However, current stiff electrode grids do not answer the need for high-resolution brain recordings and long-term biointegration. Recently, conformable electrode arrays have been proposed to achieve long-term implant stability with high performance. However, preclinical studies for these new implant technologies are needed to validate their long-term functionality and safety profile for their translation to human patients. In this context, porcine models are routinely employed in developing medical devices due to their large organ sizes and easy animal handling. However, only a few brain applications are described in the literature, mostly due to surgery limitations and integration of the implant system on a living animal.
Here, we report the method for long-term implantation (6 months) and evaluation of soft ECoG arrays in the minipig model. The study first presents the implant system, consisting of a soft microfabricated electrode array integrated with a magnetic resonance imaging (MRI)-compatible polymeric transdermal port that houses instrumentation connectors for electrophysiology recordings. Then, the study describes the surgical procedure, from subdural implantation to animal recovery. We focus on the auditory cortex as an example target area where evoked potentials are induced by acoustic stimulation. We finally describe a data acquisition sequence that includes MRI of the whole brain, implant electrochemical characterization, intraoperative and freely moving electrophysiology, and immunohistochemistry staining of the extracted brains.
This model can be used to investigate the safety and function of novel design of cortical prostheses; mandatory preclinical study to envision translation to human patients.

Subdural Soft Electrocorticography ECoG Array Implantation and Long-Term Cortical Recording in Minipigs

Here, we present a method for the long-term performance and safety assessment of soft subdural electrode arrays in a minipig model, describing surgical method and tools, postoperative magnetic resonance imaging, electrophysiology of the auditory cortex, electrochemical properties of the implant, and postmortem immunochemistry.

Neurological impairments and diseases can be diagnosed or treated using electrocorticography (ECoG) arrays. In drug-resistant epilepsy, these help ...

Bioengineering

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

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

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

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

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

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

Cerebrospinal Fluid and Blood Withdrawal from Rats with Concurrent EEG Recording

Sampling Cerebrospinal Fluid and Blood from Lateral Tail Vein in Rats During EEG Recordings

Because the composition of body fluids reflects many physiological and pathological dynamics, biological liquid samples are commonly obtained in many experimental contexts to measure molecules of interest, such as hormones, growth factors, proteins, or small non-coding RNAs. A specific example is the sampling of biological liquids in the research of biomarkers for epilepsy. In these studies, it is desirable to compare the levels of molecules in cerebrospinal fluid (CSF) and in plasma, by withdrawing CSF and plasma in parallel and considering the time distance of the sampling from and to seizures. The combined CSF and plasma sampling, coupled with video-EEG monitoring in epileptic animals, is a promising approach for the validation of putative diagnostic and prognostic biomarkers. Here, a procedure of combined CSF withdrawal from cisterna magna and blood sampling from the lateral tail vein in epileptic rats that are continuously video-EEG monitored is described. This procedure offers significant advantages over other commonly used techniques. It permits rapid sampling with minimal pain or invasiveness, and reduced time of anesthesia. Additionally, it can be used to obtain CSF and plasma samples in both tethered and telemetry EEG recorded rats, and it may be used repeatedly across multiple days of experiment. By minimizing the stress due to sampling by shortening isoflurane anesthesia, measures are expected to reflect more accurately the true levels of investigated molecules in biofluids. Depending on the availability of an appropriate analytical assay, this technique may be used to measure the levels of multiple, different molecules while performing EEG recording at the same time.

Author Spotlight: Obtaining High-Quality CSF and Blood Samples for Epilepsy Biomarker Discovery 

The protocol shows repeated cerebrospinal fluid and blood collections from epileptic rats performed in parallel with continuous video-electroencephalogram (EEG) monitoring. These are instrumental for exploring possible links between changes in various body fluid molecules and seizure activity.

Because the composition of body fluids reflects many physiological and pathological dynamics, biological liquid samples are commonly obtained in many ...

Non-restraining EEG Radiotelemetry: Epidural and Deep Intracerebral Stereotaxic EEG Electrode Placement

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