Differentiability of simulated MEG hippocampal, medial temporal and neocortical temporal epileptic spike activity

Julia M. Stephen, Doug M. Ranken, Cheryl J. Aine, Michael P. Weisend, Jerry J. Shih

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


Previous studies have shown that magnetoencephalography (MEG) can measure hippocampal activity, despite the cylindrical shape and deep location in the brain. The current study extended this work by examining the ability to differentiate the hippocampal subfields, parahippocampal cortex, and neocortical temporal sources using simulated interictal epileptic activity. A model of the hippocampus was generated on the MRIs of five subjects. CA1, CA3, and dentate gyrus of the hippocampus were activated as well as entorhinal cortex, presubiculum, and neocortical temporal cortex. In addition, pairs of sources were activated sequentially to emulate various hypotheses of mesial temporal lobe seizure generation. The simulated MEG activity was added to real background brain activity from the five subjects and modeled using a multidipole spatiotemporal modeling technique. The waveforms and source locations/ orientations for hippocampal and parahippocampal sources were differentiable from neocortical temporal sources. In addition, hippocampal and parahippocampal sources were differentiated to varying degrees depending on source. The sequential activation of hippocampal and parahippocampal sources was adequately modeled by a single source; however, these sources were not resolvable when they overlapped in time. These results suggest that MEG has the sensitivity to distinguish parahippocampal and hippocampal spike generators in mesial temporal lobe epilepsy.

Original languageEnglish (US)
Pages (from-to)388-401
Number of pages14
JournalJournal of Clinical Neurophysiology
Issue number6
StatePublished - Dec 2005


  • Hippocampus
  • Magnetoencephalography
  • Multidipole modeling
  • Simulations
  • Temporal lobe epilepsy

ASJC Scopus subject areas

  • Physiology
  • Neurology
  • Clinical Neurology
  • Physiology (medical)


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