title: Patient specific hemodynamic response functions associated with interictal discharges recorded via simultaneous intracranial EEG-fMRI.
abstract: Simultaneous collection of scalp EEG and fMRI has become an important tool for studying the hemodynamic changes associated with interictal epileptiform discharges (IEDs) in persons with epilepsy, and has become a standard presurgical assessment tool in some centres. We previously demonstrated that performing EEG-fMRI using intracranial electrodes (iEEG-fMRI) is of low risk to patients in our research centre, and offers unique insight into BOLD signal changes associated with IEDs recorded from very discrete sources. However, it is unknown whether the BOLD response corresponding to IEDs recorded by iEEG-fMRI follows the canonical hemodynamic response. We therefore scanned 11 presurgical epilepsy patients using iEEG-fMRI, and assessed the hemodynamic response associated with individual IEDs using two methods: assessment of BOLD signal changes associated with isolated IEDs at the location of the active intracranial electrode, and by estimating subject-specific impulse response functions to isolated IEDs. We found that the hemodynamic response associated with the intracranially recorded discharges varied by patient and by spike location. The observed shape and timing differences also deviated from the canonical hemodynamic response function traditionally used in many fMRI experiments. It is recommended that future iEEG-fMRI studies of IEDs use a flexible hemodynamic response model when performing parametric tests to accurately characterize these data.
authors.affiliation: Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.|Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.|Seaman Family MR Research Centre, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Craig A
authors.initials: CA
authors.lastname: Beers
authors.affiliation: Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.|Seaman Family MR Research Centre, University of Calgary, Calgary, Alberta, Canada.|Department of Radiology, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Williams
authors.affiliation: Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.|Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.|Seaman Family MR Research Centre, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Ismael
authors.initials: I
authors.lastname: Gaxiola-Valdez
authors.affiliation: Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.|Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.|Seaman Family MR Research Centre, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Pittman
authors.affiliation: Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Anita T
authors.initials: AT
authors.lastname: Kang
authors.affiliation: Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Yahya
authors.initials: Y
authors.lastname: Aghakhani
authors.affiliation: Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.|Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.|Seaman Family MR Research Centre, University of Calgary, Calgary, Alberta, Canada.|Department of Radiology, University of Calgary, Calgary, Alberta, Canada.
authors.forename: G Bruce
authors.initials: GB
authors.lastname: Pike
authors.affiliation: Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.|Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.|Seaman Family MR Research Centre, University of Calgary, Calgary, Alberta, Canada.|Department of Radiology, University of Calgary, Calgary, Alberta, Canada.|Department of Psychiatry, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Bradley G
authors.initials: BG
authors.lastname: Goodyear
authors.affiliation: Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.|Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.|Seaman Family MR Research Centre, University of Calgary, Calgary, Alberta, Canada.|Department of Radiology, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Paolo
authors.initials: P
authors.lastname: Federico
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply* / Q000503:physiopathology*; D001931:Brain Mapping; D058256:Brain Waves / Q000502:physiology*; D004569:Electroencephalography; D004827:Epilepsy / Q000473:pathology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D013997:Time Factors; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: BOLD response; epilepsy; epileptiform discharge; seizure focus