Search results for "electroencephalography"
showing 10 items of 779 documents
Acute effects on the human EEG after an external exposure to 200 ppm methanol
2001
Objectives: Even low concentrations of organic solvents may cause acute effects on the human central nervous system. The German MAK (threshold limit value) of methanol is 200 ppm. The aim of this study was to investigate whether acute exposure to 200 ppm methanol causes adverse effects, measured by EEG, and moreover, whether it is possible to differentiate between sedative and excitatory effects with this method. Methods: Twelve healthy subjects were exposed for 4 h to 200 ppm and to 20 ppm (control) in an exposure chamber in a cross-over design. The EEG was recorded before (reference) and at the end of each exposure with, the subject's eyes closed and opened and during a choice reaction te…
Spatiotemporal Neurodynamics Underlying Internally and Externally Driven Temporal Prediction: A High Spatial Resolution ERP Study
2015
Abstract Temporal prediction (TP) is a flexible and dynamic cognitive ability. Depending on the internal or external nature of information exploited to generate TP, distinct cognitive and brain mechanisms are engaged with the same final goal of reducing uncertainty about the future. In this study, we investigated the specific brain mechanisms involved in internally and externally driven TP. To this end, we employed an experimental paradigm purposely designed to elicit and compare externally and internally driven TP and a combined approach based on the application of a distributed source reconstruction modeling on a high spatial resolution electrophysiological data array. Specific spatiotemp…
ERP correlates of transposed-letter priming effects: The role of vowels versus consonants
2008
One key issue for any computational model of visual-word recognition is the choice of an input coding scheme for assigning letter position. Recent research has shown that pseudowords created by transposing two letters are very effective at activating the lexical representation of their base words (e.g., relovution activates REVOLUTION). We report a masked priming lexical decision experiment in which the pseudoword primes were created by transposing/replacing two consonants or two vowels while event-related potentials were recorded. The results showed a modulation of the amplitude at an early window (150-250 ms) and at the N400 component for vowels but not for consonant transpositions. In ad…
Think globally: Cross-linguistic variation in electrophysiological activity during sentence comprehension
2011
This paper demonstrates systematic cross-linguistic differences in the electrophysiological correlates of conflicts between form and meaning (“semantic reversal anomalies”). These engender P600 effects in English and Dutch (e.g. Kolk et al., 2003 ; Kuperberg et al., 2003), but a biphasic N400 – late positivity pattern in German (Schlesewsky and Bornkessel-Schlesewsky, 2009), and monophasic N400 effects in Turkish (Experiment 1) and Mandarin Chinese (Experiment 2). Experiment 3 revealed that, in Icelandic, semantic reversal anomalies show the English pattern with verbs requiring a position-based identification of argument roles, but the German pattern with verbs requiring a case-based identi…
Acute, subchronic and discontinuation effects of zopiclone on sleep EEG and nocturnal melatonin secretion
1996
Zopiclone is a new short half-life cyclopyrrolone hypnotic agent acting at the GABA-benzodiazepine receptor complex. In order to characterize its pharmacological profile, the effects of 7.5 mg zopiclone on nocturnal melatonin secretion were investigated under polysomnographic control in 11 healthy subjects following acute and subchronic administration as well as after abrupt discontinuation of the drug. No effect of zopiclone on the melatonin plasma levels could be observed. Regarding both total melatonin production and the temporal pattern of melatonin secretion during the night, there was no difference between placebo baseline condition, acute and subchronic administration, and discontinu…
Intra- and Interhemispheric Electroencephalogram Coherence in Siblings Discordant for Schizophrenia and Healthy Volunteers
1997
Former studies had pointed to an increased electroencephalogram (EEG) coherence in schizophrenics, but it remained unsolved whether this deviation represents the premorbid state or is only a consequence of the current or previous schizophrenic episodes. To clarify this question, we tested the hypothesis that subjects at elevated risk also reveal higher coherences compared to healthy controls. For that, intra- and interhemispheric EEG coherences were investigated in untreated schizophrenics, their healthy siblings, and healthy controls. Differences were only found regarding the intrahemispheric coherences. Both in schizophrenics and, even though to a lesser degree, in their siblings signific…
Lateralization of directional brain-heart information transfer during visual emotional elicitation
2019
Previous studies have characterized the physiological interactions between central nervous system (brain) and peripheral cardiovascular system (heart) during affective elicitation in healthy subjects; however, questions related to the directionality of this functional interplay have been gaining less attention from the scientific community. Here, we explore brain-heart interactions during visual emotional elicitation in healthy subjects using measures of Granger causality (GC), a widely used descriptor of causal influences between two dynamical systems. The proposed approach inferences causality between instantaneous cardiovagal dynamics estimated from inhomogeneous point-process models of…
A deep learning framework for automatic diagnosis of unipolar depression.
2019
Abstract Background and purpose In recent years, the development of machine learning (ML) frameworks for automatic diagnosis of unipolar depression has escalated to a next level of deep learning frameworks. However, this idea needs further validation. Therefore, this paper has proposed an electroencephalographic (EEG)-based deep learning framework that automatically discriminated depressed and healthy controls and provided the diagnosis. Basic procedures In this paper, two different deep learning architectures were proposed that utilized one dimensional convolutional neural network (1DCNN) and 1DCNN with long short-term memory (LSTM) architecture. The proposed deep learning architectures au…
Breakdown of Thalamo-Cortical Connectivity Precedes Spike Generation in Focal Epilepsies
2017
Electroencephalography (EEG) spikes and focal epileptic seizures are generated in circumscribed cerebral networks that have been insufficiently described. For precise time and spatial domain network characterization, we applied in patients with focal epilepsy dense array 256-channel EEG recordings with causal connectivity estimation by using time-resolved partial directed coherence and 3T-magnetic resonance imaging-derived cortical and thalamus integrity reconstruction. Before spike generation, significant theta and alpha bands driven information flows alterations were noted from both temporal and frontal lobes to the thalamus and from the thalamus to the frontal lobe. Medial dorsal and ven…
Reductions in circulating endocannabinoid 2-arachidonoylglycerol levels in healthy human subjects exposed to chronic stressors
2016
Increasing evidence indicates that chronic stress, such as social isolation, plays an important role in the development of a variety of psychiatric and somatic disorders. Meanwhile, chronic stress imposed by prolonged isolation and confinement in the spacecraft is also one of the major concerns for the health of future interplanetary space travelers. Preclinical studies suggest that the peripheral endocannabinoid (eCB) system is involved in the regulation of the stress response and eCB signaling is implicated in the pathogenesis of stress-related diseases. However, there are only few human studies addressing this topic, of which most focusing on patients who have already developed a certain…