Increased discharge threshold after an interictal spike in human focal epilepsy

Marco De Curtis, Laura Tassi, Giorgio Lo Russo, Roberto Mai, Massimo Cossu, Stefano Francione

Research output: Contribution to journalArticlepeer-review

Abstract

It is commonly assumed that interictal spikes (ISs) in focal epilepsies set off a period of inhibition that transiently reduces tissue excitability. Post-spike inhibition was described in experimental models but was never demonstrated in the human epileptic cortex. In the present study post-spike excitability was retrospectively evaluated on intracerebral stereo- electroencephalographic recordings performed in the epileptogenic cortex of five patients suffering from drug-resistant focal epilepsy secondary to Taylor-type neocortical dysplasias. Patients typically presented with highly periodic interictal spiking activity at 2.33 ± 0.87 Hz (mean ± SD) in the dysplastic region. During the stereo-electroencephalographic procedure, low-frequency stimulation at 1 Hz was systematically performed for diagnostic purposes to identify the epileptogenic zone. The probability of evoking an IS during the interspike period in response to 1-Hz stimuli delivered close to the ictal-onset zone was examined. Stimuli that occurred early after a spontaneous IS (within 70% of the inter-IS period) had a very low probability of generating a further IS. On the contrary, stimuli delivered during the late inter-IS period had the highest probability of evoking a further IS. The generation of stimulus-evoked ISs is occluded for several hundred milliseconds after the occurrence of a preceding spike discharge. As previously shown in animal models, these findings suggest that, during focal, periodic interictal spiking, human neocortical excitability is phasically controlled by post-spike inhibition.

Original languageEnglish
Pages (from-to)2971-2976
Number of pages6
JournalEuropean Journal of Neuroscience
Volume22
Issue number11
DOIs
Publication statusPublished - Dec 2005

Keywords

  • Focal epilepsy
  • Inhibition
  • Intracerebral stimulation
  • Neocortex
  • Stereo-electroencephalography

ASJC Scopus subject areas

  • Neuroscience(all)

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