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What is Seizure?

A seizure is an episode of increased or irregular electrical activity in the brain.  Seizures can happen in humans and other animals, of all ages, and can be due to a variety of factors; including but not limited to, chronic early life stress (Dubé et al,. 2015), a genetic predisposition, an illness, injury or nerve agent exposure.  In many cases the cause is unknown.  Seizures can occur throughout the brain (generalized) or only in a single hemisphere or location (partial or focal).  They can be a single event or be recurrent (epilepsy). The symptoms vary, dependent on type, location and severity.  Some of these signs can include freezing or zoning out, a strange feeling or sensation, loss of consciousness and violent or rhythmic muscle contractions.  The long term effects include histopathological alterations in various brain regions (Curia et al., 2008) and abnormalities in sleep (Suntsova et al., 2009). 

Types of Seizure

Seizures can be generalized or partial.  Generalized seizures affect a large portion of the brain, but not always the entire brain.  An example of a genetic model of generalized absence seizure is the WAG/Rij rat.  Similar to a type of seizure most commonly observed in children, this model shows evidence of spike wave discharges accompanied by a freezing behavior (Nersesyan et al., 2004)).  As mentioned above, partial (focal) seizures occur in a single hemisphere or brain region and can be further categorized into complex partial or simple partial seizure.  Complex partial involves a loss of consciousness while in seizures which are simple partial, consciousness is retained. (www.epilepsy.com). A temporal lobe epilepsypartial seizure) model is outline in a paper by Curia et. al. (Curia et al., 2008)..  In humans this type of epilepsy can be characterized by seizures that are simple or complex (www.epilepsy.com).

Seizure Morphology

Depending on the model or compound used, abnormal activity in the brain may present itself in various ways.  Two types of seizure are described below:

  • Absence seizure in the WAG/Rij rats presents itself in the EEG with a characteristic spike wave morphology (Nersesyan et al., 2004). 
  • Kainite induced status epilepticus starts with a low amplitude low power baseline signal, increasing in amplitude and power as the seizure progresses in severity and ending with an EEG amplitude less than baseline.

According to a review by Dr. D’Ambrosio and Dr. Miller, seizure can vary in duration and morphology.   They go on to use a definition of seizure by Dr.JH Jackson, published in 1875, as recurring discrete changes in EEG accompanied by changes in behavior (Ambrosio and Miller, 2010, Jackson, 1875). 

Seizure Models

The purpose of a model is to mimic a condition, disease or illness and/or predict efficacy or adverse effect of a treatment for a specific disease, condition or illness.  Several models in several species have been characterized and are used to test antiepileptic drugs or the increase susceptibility to seizure (the lowering of a seizure threshold).  Seizure/epilepsy models can be genetic or induced in normal animals.  Genetic models of seizure are further separated by spontaneous and reflex seizure (seizure caused by a stimulus such as sound).  Alternatively, seizure can be induced in normal animals through electrical or chemical means and these induced seizures can be acute, chronic or spontaneous/recurrent (Löscher, 2011).  New models are constantly in development to more accurately portray and treat seizures which are at present resistant to existing anti-epileptic drugs. We have created this table to provide you with more information regarding the various species and applications that have been studied in seizure research.

List of Measured Seizure Parameters (but not limited to)

  • Spectral

    • AR Spectrum

    • DFT Power Band (relative or absolute)

    • Periodogram Power Bands (relative or absolute)

    • Power Ratios

  • Marker

    • Seizure and Spikes

      • Number of Seizures or Spikes

      • Duration of Seizures or Spikes

      • Percent Coverage of Seizures or Spikes

  • Implantable Telemetry – DSI offers a variety of implant models to help researchers optimize data collection and simplify studies within this area of research. (See below).
   Biopotential Channel Count
Size  1  2  3 4 
Mouse ETA-F10, ETA-F20,
EA-F20, HD-X11		  F20-EET  -  -
Small animal CA-F40, CTA-F40,
HD-S11		  F40-EET   F50-EEE       4ET    
Large animal CTA-D70, D70-PCT,
D70-PCTP, M01		  D70-CCTP, M02  D70-EEE  

Channel Bandwidth (Hz) per Implant
ETA-, EA CTA-, CA F20-, F40- D70-, F50-, 4ET
1-200 Hz 1-200 Hz 1-50 Hz 1-100 Hz


Hardwire Solutions   

DSI’s hardwire solutions are a non-invasive method offering continuous measurement (EEG, EMG, EOG, etc.) during sleep studies with small animals.  Hardwired solutions allow the use of a tether solution to monitor up to 12 EEG/EMG channels with higher input bandwidths (0.5 Hz to 1 kHz).    

 

A setup would include use of an electrode (researcher’s choice) which would be the interface from the contact at the brain (EEG) or muscle (EMG) to the wire.  The other end of the wire would then be connected into one of DSI’s digital signal conditioners/amplifiers and partnered with DSI’s Ponemah™ software. 

 
Software Solutions

 At the core of every physiologic monitoring system is a data acquisition and analysis platform. DSI offers complete acquisition and analysis systems designed to turn physiologic signals into useable results with video integration as an option:

 

Acquisition software options:

  • PonemahTM
  • Dataquest A.R.T.TM


Software – Data Analysis

After data acquisition has taken place, DSI’s NeuroScore™ software can be used to efficiently analyze chronic data sets common to neuroscience studies.  This modular platform offers sleep scoring, seizure detection, video synchronization, and batch processing capabilities.  The following list summarizes typical use-case scenarios for several applications that are supported by the NeuroScore software:

 

Rodent Sleep

  • 2 EEG signals, 1 EMG signal, Activity
  • Slow Wave Sleep (SWS), Paradoxical Sleep, Wake, and Active Wake sleep stages can be assigned

Large Animal Sleep

  • 1 EEG Signal, 1 EOG Signal, 1 EMG Signal, Activity
  • Non- REM (N1, N2, N3), REM, Wake, and Active Wake sleep stages can be assigned

 

Seizure

  • Identify individual spikes and spike trains based on EEG amplitude thresholds and other spike characteristics

Scientific Services
DSI also offers the following services (but not limited to) for scientists needing additional assistance:

  • Study design consultation
  • Macro generation
  • Seizure data analysis with customizable reports
  • Surgical services
  • Training

 

Each of DSI’s solutions for neuroscience research consists of the recommended sensors, hardware, software, and accessories needed to reliably and accurately collect and analyze your data.

 

Shown here are common, recommended system setup diagrams for DSI’s neuroscience solutions.

 

Small Animal Implantable Telemetry System




Large Animal Implantable Telemetry System (PhysioTel Digital)





Implantable Telemetry System – Analog Output to 3rd Party Software




Hardwired Monitoring System


Authier, S., et al. “Video-electroencephalography in conscious non human primate using radiotelemetry and computerized analysis: Refinement of a safety pharmacology model”. Journal of Pharmacological and Toxicological Methods, 60.1 (2009): 88-93.

Bassett, Leanne, et al. “Telemetry video-electroencephalography (EEG) in rats, dogs and non-human primates: Methods in follow-up safety pharmacology seizure liability assessments”. Journal of Pharmacological and Toxicological Methods,  70.3 (2014): 230-240.

Cho, Kyung-Ok, et al. “Aberrant hippocampal neurogenesis contributes to epilepsy and associated cognitive decline”. Nature Communications, 6.6606 (2015).

Curia, Giulia, et al. “The pilocarpine model of temporal lobe epilepsy”. Neuroscience Methods, 172 (2008): 143-157.

Dubé, Céline M., et al. “Hyper-excitability and epilepsy generated by chronic early-life stress”. Neurobiology of Stress, 2 (2015):10-19.

D’Ambrosio, Raimondo, et al. “What is an epileptic seizure? Unifying definitions in clinical practice and animal research to develop novel treatments.” Epilepsy Currents, 10.3 (2010): 61-66.

Dürmüller, Niklaus, et al. “The use of the dog electroencephalogram (EEG) in safety pharmacology to evaluate proconvulsant risk”. Journal of Pharmacological and Toxicological Methods, 56 (2007): 234-238.

Jackson, J. Hughlings “On the anatomical investigation of epilepsy and epileptiform convulsions.” The British Medical Journal, May 10, 1873: 531-533.

Joosen, Marloes J. A., et al. “Treatment efficacy in a soman-poisoned guinea pig model: added value of physostigmine”. Organ Toxicity and Mechanisms, 85 (2011): 227-237.

Krook-Magnuson, et al. “On-demand optogenetic control of spontaneous seizures in temporal lobe epilepsy”. Nature Communications, 10.1038 (2013).

Löscher, Wolfgang. “Critical review of current animal models of seizures and epilepsy used in the discovery and development of new antiepileptic drugs”. Seizure, 20 (2011): 359-368.

Moraes, M. F. D, et. al. “A comprehensive electrographic and behavioral analysis of generalized tonic-clonic seizures of GEPR-9s”. Brain Research, 1033 (2005): 1-12.

Nersesyan, Hrachya, et al. “Dynamic fMRI and EEG Recordings During Spike-Wave Seizures and Generalized Tonic-Clonic Seizures in WAG/Rij Rats”. Journal of Cerebral Blood Flow and Metabolism, 24 (2004): 589-599.

Suntsova, N., et al. “A role for the preoptic sleep-promoting system in absence epilepsy”. Neurobiology of Disease, 36.1 (2009): 126-141.

Tse, Karen, et al. “Advantages of Repeated Low Dose against Single High Dose of Kainate in C57BL/6J Mouse Model of Status Epilepticus: Behavioral and Electroencephalographic Studies”.  PLoS ONE, 9.5 (2014): e96622.

Weiergräber, Marco, et al. “Electrocorticographic and deep intracerebral EEG recording in mice using a telemetry system.” Brain Research Protocols, 14 (2005): 154-164.