Fully automated quality assurance and localization of volumetric MEG for single-subject mapping.

Background: Robust and reproducible source mapping with magnetoencephalography is particularly challenging at the individual level. We evaluated a receiver-operating characteristic reliability (ROC-r) method for automated production of volumetric MEG maps in single-subjects. ROC-r provides quality assurance comparable to that offered by goodness-of-fit (GoF) and confidence volume (CV) for equivalent current dipole (ECD) modeling.

Improving fMRI reliability in presurgical mapping for brain tumours.

Purpose: Functional MRI (fMRI) is becoming increasingly integrated into clinical practice for presurgical mapping. Current efforts are focused on validating data quality, with reliability being a major factor. In this paper, we demonstrate the utility of a recently developed approach that uses receiver operating characteristic-reliability (ROC-r) to: (1) identify reliable versus unreliable data sets; (2) automatically select processing options to enhance data quality; and (3) automatically select individualised thresholds for activation maps.

Thresholds in fMRI studies: reliable for single subjects?

Many studies have investigated test-retest reliability of active voxel classification for fMRI, which is increasingly important for emerging clinical applications. The implicit impact of voxel-wise thresholding on this type of reliability has previously been under-appreciated. This has had two detrimental effects: (1) reliability studies use different fixed thresholds, making comparison of results is challenging; (2) typical studies do not assess reliability at the individual level, which could provide information for selecting activation thresholds.

Correspondence of visual evoked potentials with FMRI signals in human visual cortex.

Functional magnetic resonance imaging (FMRI) and event related potentials (ERPs) are tools that can be used to image brain activity with relatively good spatial and temporal resolution, respectively. Utilizing both of these methods is therefore desirable in neuroimaging studies to explore the spatio-temporal characteristics of brain function. While several studies have investigated the relationship between EEG and positive (+) BOLD (activation), little is known about the relationship between EEG signals and negative (-) BOLD (deactivation) responses.

Evaluating the spatial relationship of event-related potential and functional MRI sources in the primary visual cortex.

The integration of electroencephalogram (EEG) recordings and functional magnetic resonance imaging (fMRI) can provide considerable insight into brain functionality. However, the direct relationship between neural and hemodynamic activity is still poorly understood. Of particular interest is the spatial correspondence between event-related potential (ERP) and fMRI sources.

Exploratory data analysis reveals visuovisual interhemispheric transfer in functional magnetic resonance imaging.

We used an exploratory data analysis approach to detect interhemispheric processing of complex visual stimuli in functional magnetic resonance imaging (fMRI). A crossed-uncrossed visual field paradigm was used to elicit interhemispheric transfer of picture/word information. Under the uncrossed (control) condition, the stimuli were presented to the preferential hemispheres (pictures to the left visual field/right hemisphere and words to the right visual field/left hemisphere).

Dipole localization accuracy using grand-average EEG data sets.

Objective: Dipole localization of grand-average event related potentials only give a tentative description of the estimated underlying neural sources. This study evaluates the differences in dipole solutions between individual and group-average data sets using a standard realistic head model.

Methods: Auditory evoked potentials were recorded from 14 right-handed healthy subjects using a 64 electrode montage.

Assessing the effect of pain on demands for attentional resources using ERPs.

Event-related potentials were used as an adjunct to behavioral and self-report measures to examine the impact of pain in a short-term memory-scanning task. P3 amplitude was reduced and a frontal slow wave was increased during pain regardless of the number of items in memory. Results are discussed in terms of pain affecting an attention-switch mechanism.

Effects of dipole position, orientation and noise on the accuracy of EEG source localization.

Background: The electroencephalogram (EEG) reflects the electrical activity in the brain on the surface of scalp. A major challenge in this field is the localization of sources in the brain responsible for eliciting the EEG signal measured at the scalp. In order to estimate the location of these sources, one must correctly model the sources, i.