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Author Notes:

Corresponding Author: Peter C. Horak, 1 Medical Center Drive, Lebanon, NH, 03766, (603) 650-8374, peter.c.horak@gmail.com

We thank Blackrock Microsystems for providing neural recording equipment.

We also wish to thank the clinical and research personnel who helped collect data for the Restoring Active Memory (RAM) project.

See publication for full list of disclosures.

We confirm that we have read the Journal’s position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.

The views, opinions, and/or findings contained in this material are those of the authors and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government.


Research Funding:

This work was supported by the National Institute of Health (Grant R01-NS074450) and by the Defense Advanced Research Projects Agency (DARPA) Restoring Active Memory (RAM) program (Cooperative Agreement N66001-14-2-4032).


  • Science & Technology
  • Life Sciences & Biomedicine
  • Clinical Neurology
  • Neurosciences & Neurology
  • Interictal spikes
  • Memory
  • Electrocorticography
  • Epilepsy
  • Brain mapping
  • EEG

Interictal Epileptiform Discharges Impair Word Recall in Multiple Brain Areas

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Journal Title:



Volume 58, Number 3


, Pages 373-380

Type of Work:

Article | Post-print: After Peer Review


Interictal epileptiform discharges (IEDs) have been linked to memory impairment, but the spatial and temporal dynamics of this relationship remain elusive. In the present study, we aim to systematically characterize the brain areas and times at which IEDs affect memory. Methods: Eighty epilepsy patients participated in a delayed free recall task while undergoing intracranial electroencephalography (EEG) monitoring. We analyzed the locations and timing of IEDs relative to the behavioral data in order to measure their effects on memory. Results: Overall IED rates did not correlate with task performance across subjects (r = 0.03, p = 0.8). However, at a finer temporal scale, within-subject memory was negatively affected by IEDs during the encoding and recall periods of the task but not during the rest and distractor periods (p < 0.01, p < 0.001, p = 0.3, and p = 0.8, respectively). The effects of IEDs during encoding and recall were stronger in the left hemisphere than in the right (p < 0.05). Of six brain areas analyzed, IEDs in the inferior-temporal, medial-temporal, and parietal areas significantly affected memory (false discovery rate < 0.05). Significance: These findings reveal a network of brain areas sensitive to IEDs with key nodes in temporal as well as parietal lobes. They also demonstrate the time-dependent effects of IEDs in this network on memory.

Copyright information:

Wiley Periodicals, Inc. © 2016 International League Against Epilepsy

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