Theta activity in the hippocampus is related to specific cognitive and behavioral stages. Here, we describe an analytical method to detect highly-organized theta oscillations within the hippocampus using a time-frequency (i.e., wavelet analysis)-based approach.
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Method Article
Automatic Detection of Highly Organized Theta Oscillations in the Murine EEG
In This Article
Summary
Abstract
Theta activity is generated in the septohippocampal system and can be recorded using deep intrahippocampal electrodes and implantable electroencephalography (EEG) radiotelemetry or tether system approaches. Pharmacologically, hippocampal theta is heterogeneous (see dualistic theory) and can be differentiated into type I and type II theta. These individual EEG subtypes are related to specific cognitive and behavioral states, such as arousal, exploration, learning and memory, higher integrative functions, etc. In neurodegenerative diseases such as Alzheimer's, structural and functional alterations of the septohippocampal system can result in impaired theta activity/oscillations. A standard quantitative analysis of the hippocampal EEG includes a Fast-Fourier-Transformation (FFT)-based frequency analysis. However, this procedure does not provide details about theta activity in general and highly-organized theta oscillations in particular. In order to obtain detailed information on highly-organized theta oscillations in the hippocampus, we have developed a new analytical approach. This approach allows for time- and cost-effective quantification of the duration of highly-organized theta oscillations and their frequency characteristics.
Introduction
Theta activity in the brain is related to different cognitive and functional states, including arousal, attention, voluntary movement, exploratory behavior, attention behavior, learning and memory, somatosensory integration, and rapid eye movement (REM) sleep1,2. Principally, theta activity as a rhythmic entity can be generated in various cerebral regions and is highly organized and synchronized as theta oscillations. Below, we will focus on the analysis and quantification of theta activity/oscillations that are generated within the septohippocampal system3,....
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Protocol
All animal experimentation was performed according to the guidelines of the local and institutional Council on Animal Care (University of Bonn, BfArM, LANUV, Germany). In addition, all animal experimentation was carried out in accordance with superior legislation, e.g., the European Communities Council Directive of 24 November 1986 (86/609/EEC), or individual regional or national legislation. Specific effort was made to minimize the number of animals used, as well as their suffering.
1. Animal Housing and EEG Recording Conditions
- House mice in filter-top cages or use individually-ventilated cages.
- Transfer mic....
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Results
Theta activity can be recorded in a wide range of central nervous system (CNS) regions. Here, we present an analysis of theta oscillations from the murine hippocampus. Such oscillations can occur during different behavioral and cognitive states. It is highly recommended to analyze theta oscillations under both spontaneous long-term, task-related short-term, and pharmacologically-induced conditions.
Figure 1 illustrates a representative intrahippocampal CA1 recording u.......
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Discussion
Theta activity is of central relevance in systemic neurophysiology. It can be observed in various brain regions, particularly in the hippocampus, where it is related to specific behavioral and cognitive states. In addition, hippocampal theta can be pharmacologically differentiated into atropine-sensitive type II and atropine-insensitive type I theta. Type I is thought to be related to locomotion, such as walking or running27,28,29
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Disclosures
The authors have nothing to disclose.
Acknowledgements
The authors would like to thank Dr. Christina Ginkel (German Center for Neurodegenerative Diseases, DZNE) and Dr. Robert Stark (DZNE) for their assistance with animal breeding and animal healthcare. This work was financially supported by the Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany.
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Materials
| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| Carprofen (Rimadyl VET - Injektionslösung) | Pfizer | PZN 0110208208 | 20ml |
| binocular surgical magnification microscope | Zeiss Stemi 2000 | 0000001003877, 4355400000000, 0000001063306, 4170530000000, 4170959255000, 4551820000000, 4170959040000, 4170959050000 | |
| Dexpanthenole (Bepanthen Wund- und Heilsalbe) | Bayer | PZN: 1578818 | |
| drapes (sterile) | Hartmann | PZN 0366787 | |
| 70% ethanol | Carl Roth | 9065.5 | |
| 0.3% / 3% hydrogene peroxide solution | Sigma | 95321 | 30% stock solution |
| gloves (sterile) | Unigloves | 1570 | |
| dental glas ionomer cement | KentDental /NORDENTA | 957 321 | |
| heat-based surgical instrument sterilizer | F.S.T. | 18000-50 | |
| high-speed dental drill | Adeor | SI-1708 | |
| Inhalation narcotic system (isoflurane) | Harvard Apparatus GmbH | 34-1352, 10-1340, 34-0422, 34-1041, 34-0401, 34-1067, 72-3044, 34-0426, 34-0387, 34-0415, 69-0230 | |
| Isoflurane | Baxter 250 ml | PZN 6497131 | |
| Ketamine | Pfizer | PZN 07506004 | |
| Lactated Ringer's solution (sterile) | Braun | L7502 | |
| Nissl staining solution | Armin Baack | BAA31712159 | |
| pads (sterile) | ReWa Krankenhausbedarf | 2003/01 | |
| Steel and tungsten electrodes parylene coated | FHC Inc., USA | UEWLGESEANND | |
| stereotaxic frame | Neurostar | 51730M | ordered at Stoelting |
| (Stereo Drive-New Motorized Stereotaxic) | |||
| tapes (sterile) | BSN medical GmbH & Co. KG | 626225 | |
| TA10ETA-F20 | DSI | 270-0042-001X | Radiofrequency transmitter 3.9 g, 1.9 cc, input voltage range ± 2.5 mV, channel bandwidth (B) 1 - 200 Hz, nominal sampling rate (f) 1,000 Hz (f = 5B) temperature operating range 34 - 41 °C warranted battery life 4 months |
| TL11M2-F20EET | DSI | 270-0124-001X | Radiofrequency transmitter 3.9 g, 1.9 cc, input voltage range ± 1.25 mV, channel bandwidth (B) 1 - 50 Hz, nominal sampling rate (f) 250 Hz (f = 5B) temperature operating range 34 - 41 °C warranted battery life 1.5 months |
| Vibroslicer 5000 MZ | Electron Microscopy Sciences | 5000-005 | |
| Xylazine (Rompun) | Bayer | PZN: 1320422 | |
| Matlab | Mathworks Inc. | programming, computing and visualization software | |
| SPSS | IBM | statistical analysis software |
References
- Vanderwolf, C. H. Hippocampal electrical activity and voluntary movement in the rat. Electroencephalogr Clin Neurophysiol. 26, 407-418 (1969).
- Kahana, M. J., Seelig, D., Madsen, J. R. Theta returns. Curr Opin Neurobiol. 11, 739-744 (2001).
- Varga, V., et al.
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