Title: Human interictal epileptiform discharges are bidirectional traveling waves echoing ictal discharges

Elliot H. Smith, Jyun You Liou, Edward M. Merricks, Tyler S. Davis, Kyle Thomson, Bradley Greger, Paul A. House, Ronald G. Emerson, Robert R. Goodman, Guy M. McKhann, Sameer A. Sheth, Catherine A. Schevon, John D. Rolston

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


Summary: Interictal epileptiform discharges (IEDs), also known as interictal spikes, are large intermittent electrophysiological events observed between seizures in patients with epilepsy. Though they occur far more often than seizures, IEDs are less studied, and their relationship to seizures remains unclear. To better understand this relationship, we examined multi-day recordings of microelectrode arrays implanted in human epilepsy patients, allowing us to precisely observe the spatiotemporal propagation of IEDs, spontaneous seizures, and how they relate. These recordings showed that the majority of IEDs are traveling waves, traversing the same path as ictal discharges during seizures, and with a fixed direction relative to seizure propagation. Moreover, the majority of IEDs, like ictal discharges, were bidirectional, with one predominant and a second, less frequent antipodal direction. These results reveal a fundamental spatiotemporal similarity between IEDs and ictal discharges. These results also imply that most IEDs arise in brain tissue outside the site of seizure onset and propagate toward it, indicating that the propagation of IEDs provides useful information for localizing the seizure focus.

Original languageEnglish (US)
Article numbere73541
StatePublished - Jan 2022
Externally publishedYes


  • Electrophysiology
  • Epilepsy
  • Epileptiform discharges
  • Human
  • Ictal
  • Ictal self-organization
  • Interictal
  • Microelectrode array
  • Neuroplasticity
  • Traveling wave

ASJC Scopus subject areas

  • Neuroscience(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)


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