title: Impact of cognitive stimulation on ripples within human epileptic and non-epileptic hippocampus.
abstract: BACKGROUND
  Until now there has been no way of distinguishing between physiological and epileptic hippocampal ripples in intracranial recordings. In the present study we addressed this by investigating the effect of cognitive stimulation on interictal high frequency oscillations in the ripple range (80-250 Hz) within epileptic (EH) and non-epileptic hippocampus (NH).
  
  
  METHODS
  We analyzed depth EEG recordings in 10 patients with intractable epilepsy, in whom hippocampal activity was recorded initially during quiet wakefulness and subsequently during a simple cognitive task. Using automated detection of ripples based on amplitude of the power envelope, we analyzed ripple rate (RR) in the cognitive and resting period, within EH and NH.
  
  
  RESULTS
  Compared to quiet wakefulness we observed a significant reduction of RR during cognitive stimulation in EH, while it remained statistically marginal in NH. Further, we investigated the direct impact of cognitive stimuli on ripples (i.e. immediately post-stimulus), which showed a transient statistically significant suppression of ripples in the first second after stimuli onset in NH only.
  
  
  CONCLUSIONS
  Our results point to a differential reactivity of ripples within EH and NH to cognitive stimulation.
authors.affiliation: Behavioural and Social Neuroscience Research Group, CEITEC-Central European Institute of Technology, Masaryk University, Brno, Czech Republic. mbrazd@med.muni.cz.|Department of Neurology, Brno Epilepsy Center, St. Anne's University Hospital and Medical Faculty of Masaryk University, Pekařská 53, Brno, 65691, Czech Republic. mbrazd@med.muni.cz.
authors.forename: Milan
authors.initials: M
authors.lastname: Brázdil
authors.affiliation: International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic. jan.cimbalnik@fnusa.cz.
authors.forename: Jan
authors.initials: J
authors.lastname: Cimbálník
authors.affiliation: Behavioural and Social Neuroscience Research Group, CEITEC-Central European Institute of Technology, Masaryk University, Brno, Czech Republic. roman@med.muni.cz.|Department of Physiology, Medical Faculty of Masaryk University, Brno, Czech Republic. roman@med.muni.cz.
authors.forename: Robert
authors.initials: R
authors.lastname: Roman
authors.affiliation: Behavioural and Social Neuroscience Research Group, CEITEC-Central European Institute of Technology, Masaryk University, Brno, Czech Republic. dan.shawj@gmail.com.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Shaw
authors.affiliation: Department of Neurology, Mayo Systems Electrophysiology Laboratory, Mayo Clinic, Rochester, MN, USA. stead.squire@mayo.edu.
authors.forename: Matt M
authors.initials: MM
authors.lastname: Stead
authors.affiliation: Behavioural and Social Neuroscience Research Group, CEITEC-Central European Institute of Technology, Masaryk University, Brno, Czech Republic. pdaniel@med.muni.cz.|Department of Neurology, Brno Epilepsy Center, St. Anne's University Hospital and Medical Faculty of Masaryk University, Pekařská 53, Brno, 65691, Czech Republic. pdaniel@med.muni.cz.
authors.forename: Pavel
authors.initials: P
authors.lastname: Daniel
authors.affiliation: International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic. jurak@isibrno.cz.|Institute of Scientific Instruments, Academy of Sciences of the Czech Republic, Brno, Czech Republic. jurak@isibrno.cz.
authors.forename: Pavel
authors.initials: P
authors.lastname: Jurák
authors.affiliation: International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic. josef@isibrno.cz.|Institute of Scientific Instruments, Academy of Sciences of the Czech Republic, Brno, Czech Republic. josef@isibrno.cz.
authors.forename: Josef
authors.initials: J
authors.lastname: Halámek
mesh_terms: D000328:Adult; D003071:Cognition / Q000502:physiology*; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology*; D005260:Female; D006624:Hippocampus / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010363:Pattern Recognition, Automated; D012146:Rest; D014796:Visual Perception / Q000502:physiology; D014851:Wakefulness; D055815:Young Adult