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Simultaneous multisite LFP and SUA recordings across the hippocampal formation in a mouse model of epilepsy

Antje Kilias1, 2, 3*, Ulrich P. Froriep1, 2, 3, Arvind Kumar2, 3, Ute Häussler4, Carola A. Haas3, 4 and Ulrich Egert1, 3
  • 1 University of Freiburg, Department of Microsystems Engineering - IMTEK, Faculty of Engineering, Germany
  • 2 University of Freiburg, Faculty of Biology, Germany
  • 3 University of Freiburg, Bernstein Center Freiburg, Germany
  • 4 University of Freiburg, Department of Neurosurgery, Germany

In temporal lobe epilepsy (TLE), physiological activity within the hippocampal-entorhinal loop is severely altered, visible as recurring epileptiform activity (EA). In many cases, this is accompanied by pathological restructuring of the anatomical substrate, including widespread cell death and aberrant connectivity. These changes, known as hippocampal sclerosis, are thought to underlie EA. However, hippocampal sclerosis is apparent at any time, not only during EA, so it must also have an impact on activity during EA-free periods between epileptic events.
An animal model which reproduces a severe case of focal hippocampal sclerosis, accompanied by recurrent EA, is the intrahippocampal kainate mouse model of TLE. Using this model, we previously showed that the relation of activity in the dentate gyrus (DG) and the entorhinal cortex (EC) is changed during such EA-free periods. In particular, the theta band activity (4-8 Hz) of the DG precedes that in the EC by ~ 25 ms in epileptic mice, whereas both are synchronized under healthy conditions (Froriep et al. 2010).
To investigate the mechanism underlying this delay, a higher spatial resolution of the recordings within the hippocampal formation and the analysis of phase relationships in the local field potential (LFP) between all recording sites are required. In addition, increased temporal resolution by recording the associated single unit activity (SUA) could reveal changes in spike timing with respect to the underlying LFP. A shift in spike timing relative to the local LFP might reflect pathological plasticity whereas spike timings shifted between hippocampal structures would point to altered network properties.
Here, we addressed these questions using newly developed, custom-made silicon multisite electrode probes (Herwik et al. 2009) that facilitate simultaneous acquisition of LFP and SUA on 16 channels throughout the hippocampal formation. Chronic implantation of these probes enabled us to record both from freely behaving epileptic and control mice.
We show that these probes allow for simultaneous LFP and SUA acquisition in the DG, the hippocampus proper and parahippocampal structures and analyzed the relationship of LFP rhythms between all these sites in EA-free periods. Furthermore, we investigate the spike time relation relative to the underlying theta cycle across these locations.

Acknowledgements

Supported by the German Federal Ministry of Education and Research (BMBF, FKZ 01GQ0420, 01GQ0830) and by the Deutsche Forschungsgemeinschaft (DFG, SFB TR3, SFB 780).

References

Froriep, U.P., Kumar, A., Häussler, U., Cosandier-Rimélé, D., Haas, C. A., and Egert, U. (2010). The relation of entorhinal cortex and dentate gyrus in a model of temporal lobe epilepsy, FENS Abstr. 5, 015.14.

Herwik, S., Kisban, S., Aarts, A.A.A., Seidl, K., Girardeau, G., Benchenane, K., Zugaro, M.B., Wiener, S.I., Paul, O., Neves, H. P., and Ruther, P. (2009). Fabrication technology for silicon-based microprobe arrays used in acute and subchronic neural recording, J. Micromech. Microeng. 19, 7, 074008-074019.

Keywords: brain disease, network dysfunction and intervention

Conference: BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011, Freiburg, Germany, 4 Oct - 6 Oct, 2011.

Presentation Type: Poster

Topic: brain disease, network dysfunction and intervention (please use "brain disease, network dysfunction and intervention" as keyword)

Citation: Kilias A, Froriep UP, Kumar A, Häussler U, Haas CA and Egert U (2011). Simultaneous multisite LFP and SUA recordings across the hippocampal formation in a mouse model of epilepsy. Front. Comput. Neurosci. Conference Abstract: BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011. doi: 10.3389/conf.fncom.2011.53.00144

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Received: 23 Aug 2011; Published Online: 04 Oct 2011.

* Correspondence: Ms. Antje Kilias, University of Freiburg, Department of Microsystems Engineering - IMTEK, Faculty of Engineering, Freiburg, 79110, Germany, kilias@bcf.uni-freiburg.de