title: Modelling hemodynamic response function in epilepsy.
abstract: OBJECTIVE
  Electroencephalography and functional magnetic resonance imaging (fMRI) can be combined to noninvasively map abnormal brain activation elicited by epileptic processes. A major aim was to investigate the impact of a subject-specific hemodynamic response function (HRF) to describe the differences across patients versus the use of a standard model.
  
  
  METHODS
  We developed and applied on simulated and real data a method designed to choose optimum HRF model for identifying fMRI activation maps. In simulation, the ability of five models to reproduce data was assessed: four standard and an individual-based HRF model (ibHRF). In clinical data, drug-resistant epileptic patients underwent fMRI to investigate hemodynamic responses evoked by interictal activity.
  
  
  RESULTS
  When data are simulated with models different from the standard ones, the results obtained with ibHRF are superior to those obtained with the standard HRFs. Results on real data indicate an increase in extent and degree of activation with the ibHRF in comparison of the results obtainable using standard HRFs.
  
  
  CONCLUSIONS
  The use of the same HRF in all patients is inappropriate and resolves in biased extension of the activation maps.
  
  
  CONCLUSIONS
  The new method could represent an useful diagnostic tool for other clinical studies that may be biased because of misspecification of HRF.
authors.affiliation: Department of Neurological and Movement Sciences, Section of Neurology, University of Verona, Italy. Electronic address: silviafrancesca.storti@univr.it.
authors.forename: S F
authors.initials: SF
authors.lastname: Storti
authors.forename: E
authors.initials: E
authors.lastname: Formaggio
authors.forename: A
authors.initials: A
authors.lastname: Bertoldo
authors.forename: P
authors.initials: P
authors.lastname: Manganotti
authors.forename: A
authors.initials: A
authors.lastname: Fiaschi
authors.forename: G M
authors.initials: GM
authors.lastname: Toffolo
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology; D001931:Brain Mapping; D002560:Cerebrovascular Circulation; D004569:Electroencephalography; D004827:Epilepsy / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008955:Models, Cardiovascular
keywords: Drug-resistant epilepsy; EEG–fMRI; Hemodynamic response function; Individual-based HRF