The hemodynamic response to co-occurring interictal epileptiform discharges and high-frequency oscillations localizes the seizure-onset zone.

Objective: To use intracranial electroencephalography (EEG) to characterize functional magnetic resonance imaging (fMRI) activation maps associated with high-frequency oscillations (HFOs) (80-250 Hz) and examine their proximity to HFO- and seizure-generating tissue.

Methods: Forty-five patients implanted with intracranial depth electrodes underwent a simultaneous EEG-fMRI study at 3 T. HFOs were detected algorithmically from cleaned EEG and visually confirmed by an experienced electroencephalographer.

Mesial temporal lobe spiking reveals distinct patterns of blood oxygen level-dependent functional magnetic resonance imaging activation using simultaneous intracranial electroencephalography-functional magnetic resonance imaging.

Objective: Temporal lobe epilepsy (TLE) has a high probability of becoming drug resistant and is frequently considered for surgical intervention. However, 30% of TLE cases have nonlesional magnetic resonance imaging (MRI) scans, which is associated with worse surgical outcomes. Characterizing interactions between temporal and extratemporal structures in these patients may help understand these poor outcomes.

Mapping interictal discharges using intracranial EEG-fMRI to predict postsurgical outcomes.

Various subjective and objective methods have been proposed to identify which interictal epileptiform discharge (IED)-related EEG-functional MRI (fMRI) results are more likely to delineate seizure-generating tissue in patients with drug-resistant focal epilepsy for the purposes of surgical planning. In this intracranial EEG-fMRI study, we evaluated the utility of these methods to localize clinically relevant regions preoperatively and compared the extent of resection of these areas to postoperative outcome. Seventy patients admitted for intracranial video-EEG monitoring were recruited for a simultaneous intracranial EEG-fMRI study.

Effect of Training on Visual Identification of High Frequency Oscillations-A Delphi-Style Intervention.

Objective: We examined the effect of a simple Delphi-method feedback on visual identification of high frequency oscillations (HFOs) in the ripple (80-250 Hz) band, and assessed the impact of this training intervention on the interrater reliability and generalizability of HFO evaluations.

Methods: We employed a morphology detector to identify potential HFOs at two thresholds and presented them to visual reviewers to assess the probability of each epoch containing an HFO. We recruited 19 board-certified epileptologists with various levels of experience to complete a series of HFO evaluations during three sessions.

Localization of interictal discharge origin: A simultaneous intracranial electroencephalographic-functional magnetic resonance imaging study.

Objective: Scalp electroencephalographic (EEG)-functional magnetic resonance imaging (fMRI) studies suggest that the maximum blood oxygen level-dependent (BOLD) response to an interictal epileptiform discharge (IED) identifies the area of IED generation. However, the maximum BOLD response has also been reported in distant, seemingly irrelevant areas. Given the poor postoperative outcomes associated with extra-temporal lobe epilepsy, we hypothesized this finding is more common when analyzing extratemporal IEDs as compared to temporal IEDs.

Graph index complexity as a novel surrogate marker of high frequency oscillations in delineating the seizure onset zone.

Objective: To investigate the Graph Index Complexity (uGIC) as a marker of high frequency oscillatory (HFO) activity, the seizure onset zone (SOZ), and surgical outcome.

Methods: The SOZ, rates of HFOs at two thresholds (broad, strict), and uGIC were determined using EEG data from 41 patients. The correlation between HFOs and uGIC were calculated.

Manipulating visual scanpaths during facial emotion perception modulates functional brain activation in schizophrenia patients and controls.

Individuals with schizophrenia exhibit deficits in facial emotion processing, which have been associated with abnormalities in visual gaze behavior and functional brain activation. However, the relationship between gaze behavior and brain activation in schizophrenia remains unexamined. Studies in healthy individuals and other clinical samples indicate a relationship between gaze behavior and functional activation in brain regions implicated in facial emotion processing deficits in schizophrenia (e.

Errors in proprioceptive matching post-stroke are associated with impaired recruitment of parietal, supplementary motor, and temporal cortices.

Deficits in proprioception, the ability to discriminate the relative position and movement of our limbs, affect ~50% of stroke patients and reduce functional outcomes. Our lack of knowledge of the anatomical correlates of proprioceptive processing limits our understanding of the impact that such deficits have on recovery. This research investigated the relationship between functional impairment in brain activity and proprioception post-stroke.

Generalizability of High Frequency Oscillation Evaluations in the Ripple Band.

We examined the interrater reliability and generalizability of high-frequency oscillation (HFO) visual evaluations in the ripple (80-250 Hz) band, and established a framework for the transition of HFO analysis to routine clinical care. We were interested in the interrater reliability or epoch generalizability to describe how similar the evaluations were between reviewers, and in the reviewer generalizability to represent the consistency of the internal threshold each individual reviewer. We studied 41 adult epilepsy patients (mean age: 35.

Interrater reliability of visually evaluated high frequency oscillations.

Objective: High frequency oscillations (HFOs) and interictal epileptiform discharges (IEDs) have been shown to be markers of epileptogenic regions. However, there is currently no 'gold standard' for identifying HFOs. Accordingly, we aimed to formally characterize the interrater reliability of HFO markings to validate the current practices.

Pre-ictal BOLD alterations: Two cases of patients with focal epilepsy.

The pre-ictal state is of interest for better understanding pathophysiological processes leading up to seizures and for identifying potential biomarkers for the prediction of these events. We present two cases of patients with focal epilepsy (occipital, insular) who had seizures during functional magnetic resonance imaging (fMRI) scans. Interictal (>30min pre-seizure) control data was available for one participant.

Patient specific hemodynamic response functions associated with interictal discharges recorded via simultaneous intracranial EEG-fMRI.

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.

Co-localization between the BOLD response and epileptiform discharges recorded by simultaneous intracranial EEG-fMRI at 3 T.

Objectives: Simultaneous scalp EEG-fMRI can identify hemodynamic changes associated with the generation of interictal epileptiform discharges (IEDs), and it has the potential of becoming a standard, non-invasive technique for pre-surgical assessment of patients with medically intractable epilepsy. This study was designed to assess the BOLD response to focal IEDs recorded via simultaneous intracranial EEG-functional MRI (iEEG-fMRI).

Methods: Twelve consecutive patients undergoing intracranial video EEG monitoring were recruited for iEEG-fMRI studies at 3 T.

Feasibility of an intracranial EEG-fMRI protocol at 3T: risk assessment and image quality.

Integrating intracranial EEG (iEEG) with functional MRI (iEEG-fMRI) may help elucidate mechanisms underlying the generation of seizures. However, the introduction of iEEG electrodes in the MR environment has inherent risk and data quality implications that require consideration prior to clinical use. Previous studies of subdural and depth electrodes have confirmed low risk under specific circumstances at 1.

Intracranial EEG-fMRI analysis of focal epileptiform discharges in humans.

Purpose: Combining intracranial electroencephalography (iEEG) with functional magnetic resonance imaging (fMRI) is of interest in epilepsy studies as it would allow the detection of much smaller interictal epileptiform discharges than can be recorded using scalp EEG-fMRI. This may help elucidate the spatiotemporal mechanisms underlying the generation of interictal discharges. To our knowledge, iEEG-fMRI has never been performed at 3 Tesla (3T) in humans.

The neural correlates of the body-object interaction effect in semantic processing.

The semantic richness dimension referred to as body-object interaction (BOI) measures perceptions of the ease with which people can physically interact with words' referents. Previous studies have shown facilitated lexical and semantic processing for words rated high in BOI, e.g.

Tolerating ambiguity: ambiguous words recruit the left inferior frontal gyrus in absence of a behavioral effect.

Many models of word recognition predict a lexical ambiguity disadvantage in semantic categorization tasks (SCTs). However, recent evidence suggests that an ambiguity disadvantage in SCT results from a bias in the decision-making phase of the task and not in the meaning-activation phase: Behavioral effects of ambiguity disappear when these decision biases are controlled (Pexman, Hino, & Lupker, 2004). The current study used event-related functional magnetic resonance imaging to examine the neural correlates of ambiguity in a task that produced no behavioral ambiguity effect (i.

Gaze behavior of spotters during an air-to-ground search.

Objective: This study was designed to develop methods for evaluating the gaze behaviors of spotters during air-to-ground search and to compare field-derived measures with previous lab results. Secondary aims were to assess adherence to a prescribed scan path, evaluate search effectiveness, and determine the predictors of task success.

Background: Crashed aircraft must be located quickly to minimize loss of life, often requiring visual search from the air.