Frontiers in Computational Neuroscience (Oct 2013)

Single-unit activities during epileptic discharges in the human hippocampal formation

  • Catalina eAlvarado-Rojas,
  • Catalina eAlvarado-Rojas,
  • Katia eLehongre,
  • Katia eLehongre,
  • Juliane eBagdasaryan,
  • Juliane eBagdasaryan,
  • Anatol eBragin,
  • Richard eStaba,
  • Jerome eEngel,
  • Vincent eNavarro,
  • Vincent eNavarro,
  • Vincent eNavarro,
  • Michel eLE VAN QUYEN,
  • Michel eLE VAN QUYEN

DOI
https://doi.org/10.3389/fncom.2013.00140
Journal volume & issue
Vol. 7

Abstract

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Between seizures the brain of patients with epilepsy generates pathological patterns of synchronous activity, designated as interictal epileptiform discharges (ID). Using microelectrodes in the hippocampal formations of 8 patients with drug-resistant temporal lobe epilepsy, we studied ID by simultaneously analyzing action potentials from individual neurons and the local field potentials generated by the surrounding neuronal network. We found that ~ 30% of the units increased their firing rate during ID and 40% showed a decrease during the post-ID period. Surprisingly, 25% of units showed either an increase or decrease in firing rates several hundred of milliseconds before the ID. In 4 patients, this pre-ID neuronal firing was correlated with field high-frequency oscillations at 40-120 Hz. Finally, we observed that only a very small subset of cells showed significant coincident firing before or during ID. Taken together, we suggested that, in contrast to traditional views, ID are generated by a sparse neuronal network and followed a heterogeneous synchronization process initiated over several hundreds of milliseconds before the paroxysmal discharges.

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