Biomedical subjects

Margitta Seeck

Publications and source records attributed to Margitta Seeck.

24 records · Page 2Linked to original sources

PubMed2002

Stimulating illusory own-body perceptions.

'Out-of-body' experiences (OBEs) are curious, usually brief sensations in which a person's consciousness seems to become detached from the body and take up a remote viewing position. Here we describe the repeated induction of this experience by focal electrical stimulation of the brain's right angular gyrus in a patient who was undergoing evaluation for epilepsy treatment. Stimulation at this site also elicited illusory transformations of the patient's arm and legs (complex somatosensory responses) and whole-body displacements (vestibular responses), indicating that out-of-body experiences may reflect a failure by the brain to integrate complex somatosensory and vestibular information.

Adult↗

PubMed2002

Seizure-like phenomena and propofol: a systematic review.

Data on seizure-like phenomena (SLP) in patients receiving propofol were systematically reviewed. Reports had to provide detailed information on SLP in individual patients who received propofol. Phenomena were classified according to the time point of their occurrence during anesthesia or sedation (induction, maintenance, emergence, delayed [>30 minutes after emergence]) and their clinical presentation (generalized tonic-clonic seizures, focal motor seizures, events presented as increased tone with twitching and rhythmic movements not perceived as generalized tonic-clonic seizures, opisthotonos, involuntary movements). In 70 patients without epilepsy, SLP happened during induction in 24 (34%), during maintenance in two (3%), during emergence in 28 (40%), and was delayed in 16 (23%). Most frequent clinical presentations of SLP were generalized tonic-clonic seizures in 30 patients (43%), events presented as increased tone with twitching and rhythmic movements not perceived as generalized tonic-clonic seizures in 20 (36%), and involuntary movements in 11 (16%). Of 11 patients with epilepsy, seven (64%) had generalized tonic-clonic seizure during emergence. Of all 81 patients, 26 (32%) only had an EEG, and 12 (15%) only a neurologic consultation. SLP may happen in patients with or without epilepsy receiving propofol. The time point of the occurrence of SLP suggests that a change in cerebral concentration of propofol may be causal. To confirm this hypothesis, to estimate the prevalence of propofol-related SLP, and to identify patients at risk, data of higher quality are needed.

Adolescent↗

PubMed2002

Is the right amygdala involved in visuospatial memory? Evidence from MRI volumetric measures.

Quantitative MRI measurement of hippocampal sclerosis in patients suffering from temporal lobe epilepsy (TLE) have, as yet, failed to evidence any correlation between the right hippocampus and visuospatial memory. In this report, word learning and design learning tasks were carried out as well as MRI volumetric measurements of the hippocampus and amygdala in order to verify possible modality-specific correlations between function and structure. Delayed recall indices in our memory tasks provided significant results. Visuoverbal ratios differed between right and left TLE groups, as did laterality indices of hippocampal and amygdalar volumes. Furthermore, correlations were found between the left hippocampal volume and verbal memory, and between the right amygdala and visuospatial memory. We suggest that the difficulty encountered in establishing a correlation between right temporal structures and visuospatial memory could come both from the type of test employed and the structures considered.

Adult↗

PubMed1999

Spatiotemporal Dynamics of Human Cognition.

It is still largely unknown how the complex cortical neural network of the human brain can process information so rapidly. Multichannel evoked potential recordings with millisecond time resolution and spatiotemporal analysis methods now allow us to address this question and to unravel the temporal dynamics of the large-scale neurocognitive networks.

Journal Article↗

PubMedDate not supplied

Propagation of interictal epileptiform activity can lead to erroneous source localizations: a 128-channel EEG mapping study.

The relationship between interictal epileptiform activity and the epileptogenic zone is complex. Despite the fact that intraspike propagation may occur, the peak of the spike is often used as indicator of the site of ictal onset. In this investigation, spatio-temporal segmentation was used to demonstrate this intraspike propagation and to determine at which time point the voltage pattern corresponded best to the epileptogenic zone. Sixteen patients with focal epilepsy were recorded with 125-channel EEG. Between one and five different map topographies were identified during the rising phase of the spike. A distributed source model (EPIFOCUS) was used to localize the source of each map, and the distance from the EPIFOCUS maximum to the anatomic lesion was calculated. In only 3 of 16 cases was the entire rising phase of the spike accounted for by one single map. In another five patients, several maps were obtained, although all were located within the epileptogenic lesion. In the remaining eight patients, however, parts of the rising phase had locations outside the epileptogenic lesion. On the average, 80% of the rising time had within lesion locations the most reliable time period being halfway between onset and peak. The results illustrate that intraspike propagation has to be considered in source localizations, and they also illustrate the usefulness of spatio-temporal segmentation for visualizing this propagation.

Adolescent↗

PubMedDate not supplied

128-channel EEG source imaging in epilepsy: clinical yield and localization precision.

The authors evaluated the feasibility, clinical yield, and localization precision of high-resolution EEG source imaging of interictal epileptic activity. A consecutive series of 44 patients with intractable epilepsy of various causes, who underwent a comprehensive presurgical epilepsy evaluation, were subjected to a 128-channel EEG recording. A standardized source imaging procedure constrained to the individual gray matter was applied to the averaged spikes of each patient. In 32 patients, the presurgical workup identified a focal epileptogenic area. The 128-channel EEG source imaging correctly localized this area in 30 of these patients (93.7%). Imprecise localization was explained by simplifications of the recordings and analysis procedure, which was accepted for the benefit of speed and standardization. In a subgroup of 24 patients who underwent operations, the sublobar precision of the 128-channel EEG source imaging was evaluated by calculating the distance of the source maximum to the resected area. This analysis revealed zero distance in 19 cases (79%). The authors conclude that high-resolution interictal EEG source imaging is a valuable noninvasive functional neuroimaging technique. The speed, ease, flexibility, and low cost of this technique warrant its use in clinical practice.

Adolescent↗