Search results for "Potentials"
showing 10 items of 1072 documents
Brainstem evoked potentials and magnetic resonance imaging abnormalities in differential diagnosis of intracranial hypotension.
2019
Summary Objective To compare brainstem acoustic evoked potentials (BAEP) and magnetic resonance imaging (MRI) in the differential diagnosis of intracranial hypotension (IH), Chiari malformation (CM) and sensorineural hearing loss (SNHL). Methods BAEP were recorded in 18 IH, 18 CM, 20 SNHL patients and 52 controls. MRI were acquired in all IH and CM patients. Results Abnormal BAEP were observed in 94% of IH patients, in 33% of CM and 70% of SNHL patients. After recovery from IH, BAEP abnormalities disappeared. Internal auditory canal (IAC) MRI abnormalities were described in 88% of IH patients. MRI signs of IH were observed in 33–78% in IH patients, but the most frequent MRI sign was 8th ner…
Specific forms of neural activity associated with tactile space awareness
2002
Left tactile extinction, in which a left tactile stimulus fails to access consciousness only when a right stimulus is presented simultaneously, offers a model for studying tactile awareness from its transitory absence. Pairs of transcranial magnetic stimuli (TMS) on the parietal cortex inhibit contralateral tactile perception when separated by an interval of 1 ms. We have applied this technique on the left parietal cortex of right brain damaged (RBD) patients and normal subjects and have shown a selective lack of paired TMS inhibitory effects on right tactile perception of patients during bimanual stimulation. TMS effects were normal during unimanual right stimulation. These results suggest…
Position but not color deviants result in visual mismatch negativity in an active oddball task.
2009
Changes in the visual environment might be detected automatically. This function is provided by the sensory systems and showed, for instance, by the pop-out phenomenon. Automatic change detection is also observable within visual oddball paradigms, where rare changes are introduced in an irrelevant stimulus feature; the detection of deviant stimuli is accompanied by a negative component (so-called visual mismatch negativity) in the human event-related brain potential. In this study, the deviating stimulus feature was embedded in a task-relevant object presented in the focus of attention. With this, visual mismatch negativity was observable only with position deviants presented in the upper v…
Neural mechanisms of training an auditory event‐related potential task in a brain–computer interface context
2019
Effective use of brain-computer interfaces (BCIs) typically requires training. Improved understanding of the neural mechanisms underlying BCI training will facilitate optimisation of BCIs. The current study examined the neural mechanisms related to training for electroencephalography (EEG)-based communication with an auditory event-related potential (ERP) BCI. Neural mechanisms of training in 10 healthy volunteers were assessed with functional magnetic resonance imaging (fMRI) during an auditory ERP-based BCI task before (t1) and after (t5) three ERP-BCI training sessions outside the fMRI scanner (t2, t3, and t4). Attended stimuli were contrasted with ignored stimuli in the first-level fMRI…
Functional relevance of cross-modal plasticity in blind humans
1997
Functional imaging studies of people who were blind from an early age have revealed that their primary visual cortex can be activated by Braille reading and other tactile discrimination tasks1. Other studies have also shown that visual cortical areas can be activated by somatosensory input in blind subjects but not those with sight2,3,4,5,6,7. The significance of this cross-modal plasticity is unclear, however, as it is not known whether the visual cortex can process somatosensory information in a functionally relevant way. To address this issue, we used transcranial magnetic stimulation to disrupt the function of different cortical areas in people who were blind from an early age as they i…
Picture naming yields highly consistent cortical activation patterns: Test–retest reliability of magnetoencephalography recordings
2020
Reliable paradigms and imaging measures of individual-level brain activity are paramount when reaching from group-level research studies to clinical assessment of individual patients. Magnetoencephalography (MEG) provides a direct, non-invasive measure of cortical processing with high spatiotemporal accuracy, and is thus well suited for assessment of functional brain damage in patients with language difficulties. This MEG study aimed to identify, in a delayed picture naming paradigm, source-localized evoked activity and modulations of cortical oscillations that show high test–retest reliability across measurement days in healthy individuals, demonstrating their applicability in clinical set…
Changes in Cerebello-motor Connectivity during Procedural Learning by Actual Execution and Observation
2011
Abstract The cerebellum is involved in motor learning of new procedures both during actual execution of a motor task and during observational training. These processes are thought to depend on the activity of a neural network that involves the lateral cerebellum and primary motor cortex (M1). In this study, we used a twin-coil TMS technique to investigate whether execution and observation of a visuomotor procedural learning task is related to modulation of cerebello-motor connectivity. We observed that, at rest, a magnetic conditioning pulse applied over the lateral cerebellum reduced the motor-evoked potentials obtained by stimulating the contralateral M1, indicating activation of a cerebe…
Preattentive and attentive responses to changes in small numerosities of tones in adult humans
2016
The brain hosts a primitive number sense to non-symbolically represent numerosities of objects or events. Small exact numerosities (~4 or less) can be individuated in parallel. In contrast, large numerosities (more than ~4) can only be approximated. However, whether small numerosities can be approximated without their parallel individuation remains unclear. Parallel individuation is suggested to be an attentive process and numerical approximation an automatic process. We, therefore, tested whether small numerosities can be represented preattentively. We recorded adult humans׳ event-related potentials (ERPs) and behavioral responses to 300-ms sequences of six tones (each of either 440 Hz or …
Gesture's body orientation modulates the N400 for visual sentences primed by gestures
2020
Abstract Body orientation of gesture entails social‐communicative intention, and may thus influence how gestures are perceived and comprehended together with auditory speech during face‐to‐face communication. To date, despite the emergence of neuroscientific literature on the role of body orientation on hand action perception, limited studies have directly investigated the role of body orientation in the interaction between gesture and language. To address this research question, we carried out an electroencephalography (EEG) experiment presenting to participants (n = 21) videos of frontal and lateral communicative hand gestures of 5 s (e.g., raising a hand), followed by visually presented …
Functional properties of the brain during sleep under subchronic zopiclone administration in man.
1994
Zopiclone, a non-benzodiazepine, has been shown to be efficient in the treatment of transient, short-term or chronic sleep disorders. Apart from its hypnotic effects zopiclone has anxiolytic, anticonvulsant and myorelaxant properties and is therefore hardly distinguishable from benzodiazepines. Dependence liability and discontinuation effects have been reported to be less pronounced. Therefore zopiclone seems to be a hypnotic drug which may cause fewer side effects than conventional benzodiazepines. From the electrophysiological point of view one requires from a hypnotic drug the induction of a physiological sleep pattern as well as no alterations of information processing by the brain. The…