EEG Recording in Rodents, with a Focus on Epilepsy

C. Martín del Campo1, José L. Pérez Velázquez2, Miguel A. Cortez Freire2

1 Toronto Western Hospital, Toronto, Ontario, Canada, 2 Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
Publication Name:  Current Protocols in Neuroscience
Unit Number:  Unit 6.24
DOI:  10.1002/0471142301.ns0624s49
Online Posting Date:  October, 2009
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This unit describes the materials, methods, and analytical techniques available for the study of electrical activity of neural tissue in rodents in both homeostatic and disease states, with emphasis on epileptogenesis. A table containing a list of suppliers of relevant materials and equipment is also provided. Curr. Protoc. Neurosci. 49:6.24.1‐6.24.24. © 2009 by John Wiley & Sons, Inc.

Keywords: EEG; rodent; signal analysis; intracranial recording; epilepsy

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Table of Contents

  • Introduction
  • Background
  • Instrumentation
  • Basic Procedures
  • Signal Analysis
  • Summary
  • Literature Cited
  • Figures
  • Tables
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  •   FigureFigure 6.24.1 Radiograph of a rat with implanted telemetry equipment (reproduced with permission from Data Sciences International).
  •   FigureFigure 6.24.2 Kopf stereotaxic frame.
  •   FigureFigure 6.24.3 Schematics of a typical animal‐commutator interface. (A) insulated, single‐pole electrode; (B) socket contact; (C) multi‐channel electrode pedestal; (D) pin connector; (E) screw‐on collar; (F) cable.
  •   FigureFigure 6.24.4 Dimensions and configuration of a commercially available tetrode showing a low‐power photograph of the tetrode tip (A) and a cross‐section diagram (B) (reproduced with permission from Thomas recording GmbH).
  •   FigureFigure 6.24.5 Passive swivel (commutator).
  •   FigureFigure 6.24.6 Photograph of an electrode cap assembly after removal from a sacrificed adult rat.
  •   FigureFigure 6.24.7 Schematic of the rat cranium. Default EEG lead locations marked with Xs.
  •   FigureFigure 6.24.8 Continuous recording of a spontaneous seizure in a Wistar rat weighing 400 g, 2 weeks after implantation. The animal exhibited “stop and stare” behavior. Note sequential SWDs occurring bi‐synchronously in a “ crescendo/decrescendo” fashion (arrows). Recording parameters as in Figure .
  •   FigureFigure 6.24.9 LFP (above) and spike raster (below) from an octrode implanted into the cortex of a rat. The rat received a dose of GBL to induce absence‐like spike and wave seizures that normally appear as ∼3 Hz oscillations in the LFP recordings. The figure illustrates how population activity (LFP) and individual cell firing can be obtained from the same sensors by changing filter settings, as detailed in the text. Each box represents a 1‐sec recording from the eight sensors of the octrode.
  •   FigureFigure 6.24.10 Baseline EEG of an awake rat, one week after implantation, exploring its cage. The desynchronization in the last 2 sec of recording (voltage attenuation) occurs when the animal ceases exploratory behavior. Digitization at 200 Hz, using a 16‐channel A‐M amplifier and a Stellate Harmonie system for data acquisition and storage. Vertical bar = 75 µV. Low‐frequency filter 0.1 Hz, high‐frequency filter 70 Hz. LCA1 = left hippocampus, CA1 segment. RCtx = right cortex. Reference: 2 mm anterior to bregma.
  •   FigureFigure 6.24.11 Temporal phase synchrony during absence seizures recorded from rats. Upper traces depict four simultaneous intracerebral recordings in a rat displaying two typical spike‐wave discharges (SWD) in the cortex (Cx‐L and Cx‐R, left and right‐cortical electrodes respectively), and no apparent paroxysms in the hippocampi (Hipp‐L and Hipp‐R, left and right hippocampal electrodes). Lower color panels show the phase synchrony (color‐coded, with red the highest level of phase synchrony and blue the lowest) between the cortical recordings (upper panel) and between the two hippocampal recordings (lower). The black vertical bars signal the two SWD occurring in the cortex, the synchrony plots correspond to same length in time as the original traces above, about ∼12 seconds. Note the enhanced synchronization during the SWD between the cortical sites, at almost all frequency ranges (from 5 to 36 Hz, y axis), while the synchrony between the hippocampal electrodes shows many more fluctuations. A more detailed view of the synchronization at a specific frequency band (20 ± 2 Hz) is presented below. The plot represents the time series of the synchrony index ( R) for the neocortical recordings (lower panels). The red and black traces correspond to different smoothing of the synchrony index, R: 1000 points were averaged for the red traces, and 300 points for the black traces; note how the fine trends of the R values are better seen using this plot, compared with the more global color plots above. There is a relative increase in the R values between the two cortical electrodes during the SWD (same time scale for all panels of the figure). Modified, with permission, from Perez Velazquez et al. ().
  •   FigureFigure 6.24.12 Gamma‐butyrolactone (GBL) effect (solid line) on spike‐and‐wave discharge (SWD) duration ( y axis) per hour recordings compared to the duration of spontaneous bursts of high amplitude activity that resemble SWD in Long Evans hooded rats. The quantification of SWD is performed by visual inspection of the EEG recording over 20‐min epochs ( x axis). The y error bars are standard deviations for a group of 8 rats in the GBL and Saline groups, (p < 0.005, Student's t‐test).
  •   FigureFigure 6.24.13 (A) Human electroencephalogram (EEG) recorded during barbiturate‐induced coma, illustrating a burst‐suppression pattern. (B) Compressed Spectral Array displays intermittent peaks of activity corresponding to the paroxysmal bursts of activity on the EEG (asterisks). Recorded and analyzed online with X‐LTEK Neuroworks EEG, sampling rate 200 Hz, low‐frequency filter 0.1 Hz, high‐frequency filter 70 Hz. The first four channels display activity recorded from the left temporal region. The last four channels display the corresponding contralateral activity. The scale to the left of the CSA display ( y axis) corresponds to the relative power of each of the frequencies represented by the various colors. On the x axis is the time of day.


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