The study concerns an epileptic patient whose absence attacks were contingent on the viewing of s... more The study concerns an epileptic patient whose absence attacks were contingent on the viewing of striped patterns. A series of experiments demonstrated first that seizures were not due to the intermittent stimulation of retinal cells produced as physiological nystagmus vibrated the image of the pattern, and secondly that seizures were triggered at the cortical level, probably by the firing of complex cells. Spectacles which occluded pattern vision in one eye were highly effective in reducing seizure incidence.
Electroencephalography and clinical neurophysiology, 1998
We present a new approach for non-invasive localization of focal epileptogenic discharges in pati... more We present a new approach for non-invasive localization of focal epileptogenic discharges in patients considered for surgical treatment. EEG-triggered functional MR imaging (fMRI) and 3D EEG source localization were combined to map the primary electrical source with high spatial resolution. The method is illustrated by the case of a patient with medically intractable frontal lobe epilepsy. EEG obtained in the MRI system allowed triggering of the fMRI acquisition by the patient's habitual epileptogenic discharges. fMRI revealed multiple areas of signal enhancement. Three-dimensional EEG source localization identified the same active areas and provided evidence of onset in the left frontal lobe. Subsequent electrocorticography from subdural electrodes confirmed spike and seizure onset over this region. This approach, i.e. the combination of EEG-triggered fMRI and 3D EEG source analysis, represents a promising additional tool for presurgical epilepsy evaluation allowing precise non...
Electroencephalography and clinical neurophysiology, 1993
The recording of an EEG while the patient is undergoing magnetic resonance imaging (MRI) data acq... more The recording of an EEG while the patient is undergoing magnetic resonance imaging (MRI) data acquisition, as far as we are aware, has not been previously accomplished. By careful selection and arrangement of analog multiplexed cable-telemetry equipment to eliminate both ferrous and RF sources, a stable, readable EEG can be obtained without interfering with the diagnostic quality of the MRI. This arrangement does not cause localized heating or burning at the electrode sites. This technical capability permits more accurate neurophysiological control during the acquisition of echo planar functional MRI studies as well as providing indications of anatomical localization of electrical sources.
Electroencephalography and clinical neurophysiology, 1988
A multi-channel switched-capacitor 6-pole filter for significantly reducing the EMG artifact pres... more A multi-channel switched-capacitor 6-pole filter for significantly reducing the EMG artifact present during seizures recorded by long-term monitoring procedures has been implemented for routine use. This permits repeated replay of the seizures with different filter settings. All of the channels can be simultaneously dialed to any cut-off frequency (3 dB down) between 8 Hz and 70 Hz and the event replayed for filtering and write-out onto any standard EEG machine. The advantage of the 6-pole switched-capacitor filter is that it does not require a complex design with high precision RC components. The cut-off frequency is determined by the frequency of a simple clock that is used to select the same cut-off point for all 16 channels. By changing the clock frequency, the operator moves the cut-off point linearly. The dramatic improvement obtained by off-line digital filtering that was recently reported (Gotman et al. 1981) indicates that more efficient filtering of EMG contaminated seizur...
We previously observed tht low oral doses of melatonin given at noon increase blood melatonin con... more We previously observed tht low oral doses of melatonin given at noon increase blood melatonin concentrations to those normally occurring nocturnally and facilitate sleep onset, as assessed using and involuntary muscle relaxation test. In this study we examined the induction of polysomnographically recorded sleep by similar doses given later in the evening, close to the times of endogenous melatonin release and habitual sleep onset. Volunteers received the hormone (oral doses of 0.3 or 1.0 mg) or placebo at 6, 8, or 9 PM. Latencies to sleep onset, to stage 2 sleep, and to rapid eye movement (REM) sleep were measured polysomnographically. Either dose given at any of the three time points decreased sleep onset latency and latency to stage 2 sleep. Melatonin did not suppress REM sleep or delay its onset. Most volunteers could clearly distinguish between the effects of melatonin and those of placebo when the hormone was tested at 6 or 8 PM. Neither melatonin dose induced "hangover" effects, as assessed with mood and performance tests administered on the morning after treatment. These data provide new evidence that nocturnal melatonin secretion may be involved in physiologic sleep onset and that exogenous melatonin may be useful in treating insomnia.
We previously observed that low oral doses of melatonin given at noon increase blood melatonin co... more We previously observed that low oral doses of melatonin given at noon increase blood melatonin con- centrations to those normally occurring nocturnally and facilitate sleep onset, as assessed using an invol- untary muscle relaxation test. In this study we examined the induction of polysomnographically re- corded sleep by similar doses given later in the evening, dose to the times of
Epileptic disorders manifest with seizures and interictal epileptic discharges (IEDs). The hemody... 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...
We present the first simultaneous measurements of evoked potentials (EPs) and fMRI hemodynamic re... more We present the first simultaneous measurements of evoked potentials (EPs) and fMRI hemodynamic responses to visual stimulation. Visual evoked potentials (VEPs) were recorded both inside and outside the static 3T magnetic field, and during fMRI examination. We designed, constructed, and tested a non-magnetic 64-channel EEG recording cap. By using a large number of EEG channels it is possible to design a spatial filter capable of removing the artifact noise present when recording EEG/EPs within a strong magnetic field. We show that the designed spatial filter is capable of recovering the ballistocardiogram-contaminated original EEG signal. Isopotential plots of the electrode array recordings at the peak of the VEP response (approximately 100ms) correspond well with simultaneous fMRI observed activated areas of primary and secondary visual cortices.
It is still generally believed that complex visual analysis is not carried out within the first 1... more It is still generally believed that complex visual analysis is not carried out within the first 100 ms. Here we show that intra- and extracranial visual evoked potentials (VEPs) differentiate previously seen faces from novel faces as early as 50 ms after stimulus onset. EEG was recorded from scalp electrodes in 12 male healthy volunteers (group I) and intracranially from implanted depth electrodes in the temporal and frontal cortex of seven epilepsy patients (group II). Both groups were engaged in a face recognition task. All subjects showed significant differential responses which occurred very early (50-90 ms) and later (190-600 ms). In group II, the early responses were recorded more frequently in the right hemisphere, whereas the late differential VEPs were found in both hemispheres. Both types of VEPs were more frequent in the temporal neocortex, underlining its role as a major contributor to these fast recognition processes.
We investigated whether: (1) EEG recordings could be successfully performed in an MRI imager, (2)... more We investigated whether: (1) EEG recordings could be successfully performed in an MRI imager, (2) subclinical epileptic discharges could be used to trigger ultrafast functional MRI images, (3) artifact-free functional MRI images could be obtained while the patient was having the EEG monitored, and (4) the functional MRI images so obtained would show focal signal increases in relation to epileptic discharges. We report our results in two patients who showed focally higher signal intensity, reflective of increased local blood flow, in ultrafast functional MRI timed to epileptic discharges recorded while the patients were in the imager and compared with images not associated with discharges. One patient showed a focal increase despite a clinical and EEG history of generalized discharges. This approach may have the potential to identify brain regions activated during brief focal epileptic discharges.
The study concerns an epileptic patient whose absence attacks were contingent on the viewing of s... more The study concerns an epileptic patient whose absence attacks were contingent on the viewing of striped patterns. A series of experiments demonstrated first that seizures were not due to the intermittent stimulation of retinal cells produced as physiological nystagmus vibrated the image of the pattern, and secondly that seizures were triggered at the cortical level, probably by the firing of complex cells. Spectacles which occluded pattern vision in one eye were highly effective in reducing seizure incidence.
Electroencephalography and clinical neurophysiology, 1998
We present a new approach for non-invasive localization of focal epileptogenic discharges in pati... more We present a new approach for non-invasive localization of focal epileptogenic discharges in patients considered for surgical treatment. EEG-triggered functional MR imaging (fMRI) and 3D EEG source localization were combined to map the primary electrical source with high spatial resolution. The method is illustrated by the case of a patient with medically intractable frontal lobe epilepsy. EEG obtained in the MRI system allowed triggering of the fMRI acquisition by the patient's habitual epileptogenic discharges. fMRI revealed multiple areas of signal enhancement. Three-dimensional EEG source localization identified the same active areas and provided evidence of onset in the left frontal lobe. Subsequent electrocorticography from subdural electrodes confirmed spike and seizure onset over this region. This approach, i.e. the combination of EEG-triggered fMRI and 3D EEG source analysis, represents a promising additional tool for presurgical epilepsy evaluation allowing precise non...
Electroencephalography and clinical neurophysiology, 1993
The recording of an EEG while the patient is undergoing magnetic resonance imaging (MRI) data acq... more The recording of an EEG while the patient is undergoing magnetic resonance imaging (MRI) data acquisition, as far as we are aware, has not been previously accomplished. By careful selection and arrangement of analog multiplexed cable-telemetry equipment to eliminate both ferrous and RF sources, a stable, readable EEG can be obtained without interfering with the diagnostic quality of the MRI. This arrangement does not cause localized heating or burning at the electrode sites. This technical capability permits more accurate neurophysiological control during the acquisition of echo planar functional MRI studies as well as providing indications of anatomical localization of electrical sources.
Electroencephalography and clinical neurophysiology, 1988
A multi-channel switched-capacitor 6-pole filter for significantly reducing the EMG artifact pres... more A multi-channel switched-capacitor 6-pole filter for significantly reducing the EMG artifact present during seizures recorded by long-term monitoring procedures has been implemented for routine use. This permits repeated replay of the seizures with different filter settings. All of the channels can be simultaneously dialed to any cut-off frequency (3 dB down) between 8 Hz and 70 Hz and the event replayed for filtering and write-out onto any standard EEG machine. The advantage of the 6-pole switched-capacitor filter is that it does not require a complex design with high precision RC components. The cut-off frequency is determined by the frequency of a simple clock that is used to select the same cut-off point for all 16 channels. By changing the clock frequency, the operator moves the cut-off point linearly. The dramatic improvement obtained by off-line digital filtering that was recently reported (Gotman et al. 1981) indicates that more efficient filtering of EMG contaminated seizur...
We previously observed tht low oral doses of melatonin given at noon increase blood melatonin con... more We previously observed tht low oral doses of melatonin given at noon increase blood melatonin concentrations to those normally occurring nocturnally and facilitate sleep onset, as assessed using and involuntary muscle relaxation test. In this study we examined the induction of polysomnographically recorded sleep by similar doses given later in the evening, close to the times of endogenous melatonin release and habitual sleep onset. Volunteers received the hormone (oral doses of 0.3 or 1.0 mg) or placebo at 6, 8, or 9 PM. Latencies to sleep onset, to stage 2 sleep, and to rapid eye movement (REM) sleep were measured polysomnographically. Either dose given at any of the three time points decreased sleep onset latency and latency to stage 2 sleep. Melatonin did not suppress REM sleep or delay its onset. Most volunteers could clearly distinguish between the effects of melatonin and those of placebo when the hormone was tested at 6 or 8 PM. Neither melatonin dose induced "hangover" effects, as assessed with mood and performance tests administered on the morning after treatment. These data provide new evidence that nocturnal melatonin secretion may be involved in physiologic sleep onset and that exogenous melatonin may be useful in treating insomnia.
We previously observed that low oral doses of melatonin given at noon increase blood melatonin co... more We previously observed that low oral doses of melatonin given at noon increase blood melatonin con- centrations to those normally occurring nocturnally and facilitate sleep onset, as assessed using an invol- untary muscle relaxation test. In this study we examined the induction of polysomnographically re- corded sleep by similar doses given later in the evening, dose to the times of
Epileptic disorders manifest with seizures and interictal epileptic discharges (IEDs). The hemody... 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...
We present the first simultaneous measurements of evoked potentials (EPs) and fMRI hemodynamic re... more We present the first simultaneous measurements of evoked potentials (EPs) and fMRI hemodynamic responses to visual stimulation. Visual evoked potentials (VEPs) were recorded both inside and outside the static 3T magnetic field, and during fMRI examination. We designed, constructed, and tested a non-magnetic 64-channel EEG recording cap. By using a large number of EEG channels it is possible to design a spatial filter capable of removing the artifact noise present when recording EEG/EPs within a strong magnetic field. We show that the designed spatial filter is capable of recovering the ballistocardiogram-contaminated original EEG signal. Isopotential plots of the electrode array recordings at the peak of the VEP response (approximately 100ms) correspond well with simultaneous fMRI observed activated areas of primary and secondary visual cortices.
It is still generally believed that complex visual analysis is not carried out within the first 1... more It is still generally believed that complex visual analysis is not carried out within the first 100 ms. Here we show that intra- and extracranial visual evoked potentials (VEPs) differentiate previously seen faces from novel faces as early as 50 ms after stimulus onset. EEG was recorded from scalp electrodes in 12 male healthy volunteers (group I) and intracranially from implanted depth electrodes in the temporal and frontal cortex of seven epilepsy patients (group II). Both groups were engaged in a face recognition task. All subjects showed significant differential responses which occurred very early (50-90 ms) and later (190-600 ms). In group II, the early responses were recorded more frequently in the right hemisphere, whereas the late differential VEPs were found in both hemispheres. Both types of VEPs were more frequent in the temporal neocortex, underlining its role as a major contributor to these fast recognition processes.
We investigated whether: (1) EEG recordings could be successfully performed in an MRI imager, (2)... more We investigated whether: (1) EEG recordings could be successfully performed in an MRI imager, (2) subclinical epileptic discharges could be used to trigger ultrafast functional MRI images, (3) artifact-free functional MRI images could be obtained while the patient was having the EEG monitored, and (4) the functional MRI images so obtained would show focal signal increases in relation to epileptic discharges. We report our results in two patients who showed focally higher signal intensity, reflective of increased local blood flow, in ultrafast functional MRI timed to epileptic discharges recorded while the patients were in the imager and compared with images not associated with discharges. One patient showed a focal increase despite a clinical and EEG history of generalized discharges. This approach may have the potential to identify brain regions activated during brief focal epileptic discharges.
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