Electrical cortical stimulation of the human frontal gyri and the precentral gyrus has been shown to induce eye movements and it has classically been assumed that these stimulation-induced eye movements result from electrical interference with the human homologue of the monkey frontal eye field (FEF). However, amplitude of electrical current and induced type of eye movement, which are essential for the determination of eye fields in the monkey, have not been investigated systematically in man. We applied electrical cortical stimulation in the lateral frontal cortex in six epileptic patients. Sites whose stimulation resulted in eye movements were determined with respect to gyral and sulcal patterns, Talairach coordinates and neighboring functions as found by electrical cortical stimulation. Based on this approach, a restricted location of the electrically defined FEF is proposed within a larger oculomotor region on the posterior part of the middle frontal gyrus.
The use of screen electronic devices in the evening negatively affects sleep. Yet, sleep is known to be essential for brain maturation and a key factor for good academic performance, and thus is particularly critical during childhood and adolescence. Although previous studies reported associations between screen time and sleep impairment, their causal relationship in adolescents remains unclear. Using actigraphy and daily questionnaires in a large sample of students (12 to 19 years old), we assessed screen time in the evening and sleep habits over 1 month. This included a 2 week baseline phase, followed by a 40 min sleep education workshop and a 2 week interventional phase, in which participants were asked to stop using screen devices after 9 pm during school nights. During the interventional phase, we found that the reduction of screen time after 9 pm correlated with earlier sleep onset time and increased total sleep duration. The latter led to improved daytime vigilance. These findings provide evidence that restricting screen use in the evening represents a valid and promising approach for improving sleep duration in adolescents, with potential implications for daytime functioning and health.
Article abstract-Background: Various structural and functional changes, such as focal edema, blood flow, and metabolism, occur in the cerebral cortex after focal status epilepticus. These changes can be assessed noninvasively by means of MRI techniques, such as fluid-attenuated inversion recovery (FLAIR), EEG-triggered functional MRI (EEG-fMRI), and proton MR spectroscopy (MRS). Methods: The authors report on a 40-year-old patient with nonlesional partial epilepsy in the left posterior quadrant in whom these MRI techniques were applied in an active seizure focus and repeated during a follow-up of 1 year. Results: FLAIR imaging taken at the time of status epilepticus showed a signal hyperintensity in the occipital region.
The possibility of combining the high spatial resolution of functional magnetic resonance imaging (fMRI) with the high temporal resolution of electroencephalography (EEG) may provide a new tool in cognitive neurophysiology, as well as in clinical applications such as epilepsy. However, the simultaneous recording of EEG and fMRI raises important practical problems: 1) the patients' safety, in particular the risk of skin burns due to electrodes heating; 2) the impairment of the EEG recording by the static magnetic field, as well as by RF and magnetic field gradients used during MRI; and 3) the quality of MR images, which may be affected by the presence of conductors and electronic devices in the MRI bore. Index terms: functional MRI; EEG; artifact; temperature; safety THE POSSIBILITY TO RECORD multichannel electroencephalogram (EEG) in the magnet (1) may offer new insights in the investigation of brain functions. The combination of two techniques, EEG and functional magnetic resonance imaging (fMRI), may yield a new neuroimaging tool that combines the excellent temporal resolution of the EEG with the good spatial resolution of fMRI (2). Such a tool could be used in both cognitive neuroscience and clinical neurology, such as epilepsy (3). Several studies have successfully applied EEG-triggered fMRI to visualize brain regions related to the generation of epileptogenic spikes (4 -6), but little has been done in cognitive neurosciences (7).Potential problems may appear when concurrent EEG and fMRI acquisition is performed. On the one hand, the presence of electrodes in the image field of view (FOV) may produce MRI artifacts due to susceptibility effect or radiofrequency (RF) interaction with the conductive wires. On the other hand, the EEG recording may be impaired by the presence of the main magnetic field (B 0 ), as well as by RF and switched gradients used during MRI acquisitions. Although methods have been proposed to restore electrophysiological signals during MR acquisition (8), no attempt has been made to implement this solution in practice-the principal reason being the difficulty to avoid preamplifier saturation of EEG systems due to induced current by switched gradients. Moreover, if fMRI is triggered by EEG-measured signals, good quality EEG recordings between MR acquisitions, rather than during MR scanning, are required. In the latter situation, only B 0 affects the quality of the EEG recording, producing electrocardiogram artifacts (1,9,10). However, it has been shown by different research groups that a good quality EEG recording can be obtained inside a 1.5 T magnet, allowing the detection of epileptic discharges (4 -6,11).Another important concern is the safety of the patient associated with the use of the EEG device during MRI acquisition. This risk is due to induced currents in EEG conductors, which can be caused by the static magnetic field, switching magnetic gradient fields, or RF interaction. A recent theoretical article reviewed the different mechanisms that induce currents in electrical wires us...
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