Research Interests:
Research Interests: Engineering, Computer Science, Electrophysiology, Electroencephalography, Computer Hardware, and 15 moreNanotechnology, Medicine, Instrumentation, Humans, Noise, Data acquisition, Care, Data Collection, Multiplexer, Clinical Neurophysiology, Electrodes, Amplifier, Electrode, Data Acquisition System, and Medical and Health Sciences
Research Interests:
Research Interests: Engineering, Biomedical Engineering, Brain Imaging, Magnetic Resonance Imaging, Epilepsy, and 15 moreFunctional MRI, Electroencephalography, Image Quality, Humans, Functional Imaging, Artifacts, Electroencephalogram, Clinical Neurophysiology, Intensive Care Unit, Clinical Study, Long Term Monitoring, Intensive Care Units, Electrodes, Bandages, and Magnetic resonance image
Research Interests:
The combination of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) has been shown to have great potential for providing a greater understanding of normal and diseased states in both human and animal studies.... more
The combination of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) has been shown to have great potential for providing a greater understanding of normal and diseased states in both human and animal studies. Simultaneous EEG-fMRI is particularly well suited for the study of epilepsy in that it may reveal the neurobiology of ictal and interictal epileptiform discharges and noninvasively localize epileptogenic foci. Spontaneous, coherent fluctuations of neuronal activity and the coupled hemodynamic responses have also been shown to provide diagnostic markers of disease, extending our understanding of intrinsically structured ongoing brain activity. Following a short summary of the hardware and software development of simultaneous EEG-fMRI, this paper reviews a unified framework of integrating neuronal and hemodynamic processes during epileptic seizures and discusses the role and impact of spontaneous activity in the mesial temporal lobe epilepsies with pa...
Research Interests:
Research Interests:
Research Interests:
Research Interests: Engineering, Computer Science, Electrophysiology, Electroencephalography, Computer Hardware, and 15 moreNanotechnology, Medicine, Instrumentation, Humans, Noise, Data acquisition, Care, Data Collection, Multiplexer, Clinical Neurophysiology, Electrodes, Amplifier, Electrode, Data Acquisition System, and Medical and Health Sciences
Research Interests: Engineering, Biomedical Engineering, Brain Imaging, Magnetic Resonance Imaging, Epilepsy, and 15 moreFunctional MRI, Electroencephalography, Image Quality, Humans, Functional Imaging, Artifacts, Electroencephalogram, Clinical Neurophysiology, Intensive Care Unit, Clinical Study, Long Term Monitoring, Intensive Care Units, Electrodes, Bandages, and Magnetic resonance image
Research Interests:
Research Interests: Neuroscience, Psychology, Cognitive Science, Materials Science, Nuclear Magnetic Resonance, and 15 moreMedicine, Magnetic field, Brain, Humans, Female, Electromagnetic Induction, Electromagnetic Fields, Artifacts, Current Density, Human Brain, Adult, Neurosciences, Brain injuries, Electromagnetic coil, and Electric stimulation
Research Interests: Neuroscience, Computer Science, Audiology, Attention, Electroencephalography, and 15 moreMedicine, Low Frequency, Higher Order Thinking, Brain Mapping, Humans, Female, Neuroimage, Male, Electromagnetic Fields, Adult, Healthy Subjects, Alpha Rhythm, Cortical Excitability, Higher order, and Medical and Health Sciences
The ability to trigger functional magnetic resonance imaging (fMRI) acquisitions related to the occurrence of EEG-based physiologic transients has changed the field of fMRI into a more dynamically based technique. By knowing the temporal... more
The ability to trigger functional magnetic resonance imaging (fMRI) acquisitions related to the occurrence of EEG-based physiologic transients has changed the field of fMRI into a more dynamically based technique. By knowing the temporal relationship between focal increases in neuronal firing rates and the provoked focal increase in blood flow, investigators are able to maximize the fMR-linked images that show where the activity originates. Our mastery of recording EEG inside the bore of a MR scanner has also allowed us to develop cognitive paradigms that record not only the fMR BOLD images, but also the evoked potentials (EPs). The EPs can subsequently be subjected to localization paradigms that can be compared to the localization seen on the BOLD images. These two techniques will most probably be complimentary. BOLD responses are dependent on a focal increase in metabolic demand while the EPs may or may not be related to energy demand increases. Additionally, recording EPs require that the source or sources of that potential come from an area that is able to generate far-field potentials. These potentials are related to the laminar organization of the neuronal population generating that potential. As best we know the BOLD response does not depend on any inherent laminar neuronal organization. Therefore, by merging these two recording methods, it is likely that we will gain a more detailed understanding of not only the areas involved in certain physiologic events, e.g. focal epilepsy or cognitive processing, but also on the sequencing of the activation of the various participating regions.
Research Interests: Neuroscience, Computer Science, Magnetic Resonance Imaging, Epilepsy, Electroencephalography, and 15 moreNeurophysiology, Medicine, Evoked Potentials, Humans, Functional Magnetic Resonance Imaging, Clinical, Artifacts, Clinical Sciences, Clinical Neurophysiology, Image Enhancement, Electrodes, Equipment Design, Neurosciences, Brain Diseases, and Magnetic resonance image
The incidences of spikes and paroxysmal rhythmic events (PREs) in 10-h overnight EEGs of normal adult volunteers (n=135) were studied at 11 sites with a computer-assisted ambulatory EEG monitoring system with automatic spike and PRE... more
The incidences of spikes and paroxysmal rhythmic events (PREs) in 10-h overnight EEGs of normal adult volunteers (n=135) were studied at 11 sites with a computer-assisted ambulatory EEG monitoring system with automatic spike and PRE detection. Spikes were evident in the overnight EEG of 1 subject (0.7%), and PREs were apparent in the overnight EEG of the same subject (0.7%). The incidences of spikes of 24 other subjects with a history of migraine and/or a family history of epilepsy were 12.5 and 13.3%, respectively. The overnight EEGs of these subjects were significantly more likely to show spikes than the overnight EEGs of subjects without migraine or a family history of epilepsy.
Research Interests:
Measurement of the EEG during fMRI scanning can give rise to image distortions due to magnetic susceptibility, eddy currents or chemical shift artifacts caused by certain types of EEG electrodes, cream, leads, or amplifiers. Two different... more
Measurement of the EEG during fMRI scanning can give rise to image distortions due to magnetic susceptibility, eddy currents or chemical shift artifacts caused by certain types of EEG electrodes, cream, leads, or amplifiers. Two different creams were tested using MRS and T2* measurements, and we found that the one with higher water content was superior. This study introduces an index that quantifies the influence of EEG equipment on the BOLD fMRI signal. This index can also be used more generally to measure the changes in the fMRI signal due to the presence of any type of device inside (or outside) of the field of view (e.g., with fMRI and diffuse optical tomography, infrared imaging, transcranial magnetic stimulation, ultrasound imaging, etc.). Quantitative noise measurements are hampered by the normal variability of functional activation within the same subject and by the different slice profiles obtained when inserting a subject multiple times inside a MR imaging system. Our meas...
Research Interests:
Research Interests: Engineering, Neuroscience, Psychology, Electrophysiology, Electroencephalography, and 15 moreMedicine, Brain Mapping, Humans, Female, Male, Human Brain, Clinical Neurophysiology, Adult, Neuronal Activity, Occipital Lobe, Rate Limiting, photic stimulation, Psychology and Cognitive Sciences, Medical and Health Sciences, and Electric stimulation
Research Interests:
The accuracy with which electrical sources in the brain can be localized by using electroencephalograms measured on the scalp is not well known. In this study, tests of localization accuracy were performed by using implanted dipolar... more
The accuracy with which electrical sources in the brain can be localized by using electroencephalograms measured on the scalp is not well known. In this study, tests of localization accuracy were performed by using implanted dipolar sources in the human brain. These dipoles are created by passing a weak (subthreshold) current through intracerebral electrodes implanted in the brains of epileptic patients for seizure monitoring. The locations of these dipoles are accurately known from roentgenographs. First, 16 electroencephalograms produced by these dipoles were recorded, then inverse solutions were calculated for the apparent sources of these electroencephalograms. Finally, the locations of the apparent sources were compared with the known locations of the implanted dipoles to determine localization error. The average localization error for a total of 28 dipoles in 3 subjects was 1.1 cm. These results indicate that good localization accuracy for focal sources in the brain can be pro...
Research Interests:
Evoked potentials to visually driven cognitive tasks were recorded through depth electrodes placed bilaterally within the amygdala, hippocampus, midtemporal and inferotemporal cortex, and lateral frontal cortex of 6 epileptic patients.... more
Evoked potentials to visually driven cognitive tasks were recorded through depth electrodes placed bilaterally within the amygdala, hippocampus, midtemporal and inferotemporal cortex, and lateral frontal cortex of 6 epileptic patients. Task‐related differential response patterns were used to identify the recording sites engaged by specific aspects of visual encoding. In this group of 6 patients, the amygdala was most frequently engaged in encoding the familiarity of faces; midtemporal and inferotemporal cortex, in encoding perceptual identity and object categorization; and lateral frontal cortex, in holding visual object information in working memory. The two aspects of encoding that most frequently engaged the hippocampal region were related to working memory and object categorization. The processing of complex visual knowledge is thus anatomically distributed but regionally specialized. These experiments also showed that identical input and output parameters can engage different a...
Research Interests: Neuroscience, Psychology, Magnetic Resonance Imaging, Categorization, Medicine, and 14 moreHippocampus, Temporal Lobe, Humans, Distributed Processing, Female, Male, Human Brain, Clinical Sciences, Adult, Visual Evoked Potentials, Neurosciences, Frontal Lobe, Visual object recognition, and photic stimulation
METHODS: Twenty patients with epilepsy and frequent interictal discharges were studied with concurrent EEG monitoring on a 1.5-T echo-planar magnet to acquire blood-oxygenation-leveldependent (BOLD) images in the baseline (OFF) and ...
Research Interests:
Research Interests: Neuroscience, Psychology, Magnetoencephalography, Magnetic Resonance Imaging, Epilepsy, and 15 moreFunctional MRI, Localization, Electroencephalography, Adolescent, Medicine, Source Code Analysis, Humans, Source Localization, Female, Electrocorticography, Mr Imaging, High Spatial Resolution, Frontal Lobe, Frontal Lobe Epilepsy, and Source analysis
Research Interests: Engineering, Psychology, Electrophysiology, Animal Studies, Electroencephalography, and 15 moreMedicine, Safety, Dogs, Humans, Mice, Animals, Human Animation, Electroencephalogram, Clinical Neurophysiology, Rats, Electrodes, Amplifier, Electrode, Psychology and Cognitive Sciences, and Medical and Health Sciences
Epileptic disorders manifest with seizures and interictal epileptic discharges (IEDs). The hemodynamic changes that accompany IEDs are poorly understood and may be critical for understanding epileptogenesis. Despite a known linear... more
Epileptic disorders manifest with seizures and interictal epileptic discharges (IEDs). The hemodynamic changes that accompany IEDs are poorly understood and may be critical for understanding epileptogenesis. Despite a known linear coupling of the neurovascular elements in normal brain tissues, previous simultaneous electroencephalography (EEG)-functional magnetic resonance imaging (fMRI) studies have shown variable correlations between epileptic discharges and blood oxygenation level-dependent (BOLD) response, partly because most previous studies assumed particular hemodynamic properties in normal brain tissue. The occurrence of IEDs in human subjects is unpredictable. Therefore, an animal model with reproducible stereotyped IEDs was developed by the focal injection of penicillin into the right occipital cortex of rats anesthetized with isoflurane. Simultaneous EEG-fMRI was used to study the hemodynamic changes during IEDs. A hybrid of temporal independent component analysis (ICA) o...
Research Interests: Computer Science, Magnetic Resonance Imaging, Epilepsy, Independent Component Analysis, Electroencephalography, and 15 moreMedicine, Linear models, Evoked Potentials, Functional Magnetic Resonance Imaging, Animals, Male, Magnetic Resonance, Animal Model, Ictal, General Linear Model, Human Subjects, Impulse Response Function, Linear Transformation, Magnetic resonance image, and Medical and Health Sciences
Simultaneous recording of electroencephalogram (EEG) and functional MRI (fMRI) or MR spectroscopy (MRS) can provide further insight into our understanding of the underlying mechanisms of neurologic disorders. Current technology for... more
Simultaneous recording of electroencephalogram (EEG) and functional MRI (fMRI) or MR spectroscopy (MRS) can provide further insight into our understanding of the underlying mechanisms of neurologic disorders. Current technology for simultaneous EEG and MRI recording is limited by extensive postacquisition processing of the data. Real-time display of artifact-free EEG recording during fMRI/MRS studies is essential in studies that involve epilepsy to ensure that they address specific EEG features such as epileptic spikes or seizures. By optimizing the EEG recording equipment to maximize the common mode rejection ratio of its amplifiers, a unique EEG system was designed and tested that allowed real-time display of the artifact-free EEG during fMRI/MRS in an animal model of epilepsy. Spike recordings were optimized by suppression of the background EEG activity using fast-acting and easily controlled inhalational anesthesia. Artifact suppression efficiency of 70-100% was achieved following direct subtraction of referentially recorded filtered EEG tracings from active electrodes, which were located in close proximity to each other (over homologous occipital cortices) and a reference electrode. Two independent postacquisition processing tools, independent component analysis and direct subtraction of unfiltered digital EEG data in MATLAB, were used to verify the accuracy of real-time EEG display.
Research Interests: Computer Science, Algorithms, Biomedical Engineering, Magnetic Resonance Imaging, Epilepsy, and 15 moreElectroencephalography, Magnetic Resonance Spectroscopy, Medicine, Brain Mapping, Computer Systems, Functional Magnetic Resonance Imaging, Animals, Male, Animal Model, Artifacts, Real Time, Rats, Magnetic, Amplifiers, and Penicillins
Maintaining a stable physiologic state is essential when studying animal models of epilepsy with simultaneous electroencephalograph (EEG) and functional magnetic resonance imaging (fMRI) or EEG and magnetic resonance spectroscopy (MRS).... more
Maintaining a stable physiologic state is essential when studying animal models of epilepsy with simultaneous electroencephalograph (EEG) and functional magnetic resonance imaging (fMRI) or EEG and magnetic resonance spectroscopy (MRS). To achieve and maintain such stability in rats in the MRI environment, a minimally invasive but comprehensive system was developed to monitor body temperature, heart rate, blood pressure, blood oxygen saturation and end-tidal CO2 (ETCO2) of expired gas. All physiologic parameters were successfully monitored in Sprague-Dawley rats without interfering with EEG recordings during simultaneous fMRI and MRS studies. Body temperature, heart rate, blood pressure, blood oxygen saturation, and ETCO2, were maintained between 36.5 and 37.5 degrees C, 250-450 beats/min, 136+/-17 mmHg, >90%, and 20-35 mmHg, respectively for 6-8 h under inhalational anesthesia. This set-up could be extended to study in vivo applications in other laboratory animals with only minor modifications.