W Lalouschek, W Gerschlager, J Lehrner, C Baumgartner, G Lindinger, L Deecke, W Lang
{"title":"Event-related potentials in patients with temporal lobe epilepsy reveal topography specific lateralization in relation to the side of the epileptic focus","authors":"W Lalouschek, W Gerschlager, J Lehrner, C Baumgartner, G Lindinger, L Deecke, W Lang","doi":"10.1016/S0168-5597(98)00037-9","DOIUrl":"10.1016/S0168-5597(98)00037-9","url":null,"abstract":"<div><p>Event-related potentials (ERPs) were recorded during a continuous recognition memory paradigm in patients with left-sided (LTLE; <em>n</em><span>=8) or right-sided temporal lobe epilepsy (RTLE; </span><em>n</em>=6), and in healthy control subjects (<em>n</em><span>=24). Control subjects and both patient groups exhibited consistent OLD/NEW ERP-differences from 200–600 ms after stimulus onset. ERPs did not differ significantly between LTLE and RTLE patients, with respect to OLD/NEW distinction or the type of presented material (verbal vs. non-verbal). However, ERP topography showed significant differences between LTLE and RTLE patients: in lateral fronto-temporal recordings, patients showed larger negativities contralateral to the seizure focus, whereas we found larger negativities ipsilateral to the seizure focus in parietal recordings. Differences between the groups were significant from 300 to 600 ms post-stimulus. As a consequence, the amplitude gradient from fronto-temporal to parietal recordings was higher on the right side in LTLE patients and on the left side in RTLE patients. Again, differences between LTLE and RTLE patients were highly significant. We assume that ERPs reflect disturbances of a cortico-cortical network dependent on the side of the seizure focus in temporal lobe epilepsy. Furthermore, scalp-recorded ERPs might be a useful tool in the prediction of the side of the seizure focus in patients with temporal lobe epilepsy.</span></p></div>","PeriodicalId":100401,"journal":{"name":"Electroencephalography and Clinical Neurophysiology/Evoked Potentials Section","volume":"108 6","pages":"Pages 567-576"},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0168-5597(98)00037-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20780987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
U Baumgärtner , H Vogel , J Ellrich , J Gawehn , P Stoeter , R.-D Treede
{"title":"Brain electrical source analysis of primary cortical components of the tibial nerve somatosensory evoked potential using regional sources","authors":"U Baumgärtner , H Vogel , J Ellrich , J Gawehn , P Stoeter , R.-D Treede","doi":"10.1016/S0168-5597(98)00040-9","DOIUrl":"10.1016/S0168-5597(98)00040-9","url":null,"abstract":"<div><p><span><span>Tibial nerve </span>somatosensory evoked potentials<span> (SEPs) show higher amplitudes ipsilateral to the side of stimulation, whereas subdural recordings revealed a source in the foot area of the contralateral hemisphere. We now investigated this paradoxical lateralization by performing a brain electrical source analysis in the P40 time window (34–46 ms). The tibial nerve was stimulated behind the ankle (8 subjects). On each side, 2048 stimuli were applied twice. SEPs were recorded using 32 magnetic resonance imaging (MRI)-verified electrode positions (bandpass 0.5–500 Hz). In each case, the P40 amplitude was higher ipsilaterally (0.45±0.14 </span></span><em>μ</em>V) than contralaterally (−0.49±0.16 <em>μ</em><span>V). The best fitting regional source, however, was always located in the contralateral hemisphere with a mean distance of 8.2±4.3 mm from the midline. The positivity pointed ipsilaterally shifting from a frontal orientation (P37) to a parietal direction (P40). The P40 dipole moment was 2.5 times stronger than the dipole moment of P37, which makes P40 most prominent in EEG recordings. However, with its oblique dipole orientation compared to the tangential P37 dipole, it is systematically underestimated in MEG. Dipole orientations explained interindividual variability of scalp potential distribution. SEP amplitudes were smaller when generated in the dominant (left) hemisphere. This is explained by deeper located sources (5.4±1.6 mm) with a more tangential orientation (</span><em>Δϑ</em>=17.5±2.3°) in the left hemisphere.</p></div>","PeriodicalId":100401,"journal":{"name":"Electroencephalography and Clinical Neurophysiology/Evoked Potentials Section","volume":"108 6","pages":"Pages 588-599"},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0168-5597(98)00040-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20780990","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Meier , T. Rosburg , M. Arnold , I. Kreitschmann-Andermahr , H. Sauer , H. Nowak , H. Witte
{"title":"Quantification and rejection of ocular artifacts in auditory evoked fields in schizophrenics","authors":"T. Meier , T. Rosburg , M. Arnold , I. Kreitschmann-Andermahr , H. Sauer , H. Nowak , H. Witte","doi":"10.1016/S0168-5597(98)00031-8","DOIUrl":"10.1016/S0168-5597(98)00031-8","url":null,"abstract":"<div><p><strong>Results</strong>: In a magnetoencephalographic investigation of the auditory evoked field (AEF) in 17 schizophrenics and 17 controls, 37% of the schizophrenics and 12% of the controls showed eye artifacts in every second trial or even more frequently. In the uncorrected average fields, the ratio between the power of artifacts and the power of the magnetoencephalogram (MEG) exceeded the value of 0.1 for 48% of the schizophrenics and for 29% of the controls. Ocular artifacts biased the locations of equivalent current dipoles of the M100 component towards deeper positions. A regression algorithm for the correction of ocular artifacts in raw data and an identification technique of ocular artifacts based on the topography of transmission coefficients is described.</p><p><strong>Conclusions</strong>: A linear dependence of ocular artifacts in AEF on the electrooculogram (EOG) was confirmed. Possible errors introduced by the correction are discussed. Transmission coefficients should be calculated for several individual trials with the same type of artifact. Errors due to evoked potentials in the EOG were found to be comparable in amplitude to noise in the AEF. Examples of transmission coefficients from the EOG to the MEG are given.</p></div>","PeriodicalId":100401,"journal":{"name":"Electroencephalography and Clinical Neurophysiology/Evoked Potentials Section","volume":"108 6","pages":"Pages 526-535"},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0168-5597(98)00031-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20780421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"P9 in median nerve SEPs is a junctional potential generated by the change of the volume conductor size between trunk and neck","authors":"Atsuko Mochizuki , Masahiro Sonoo , Teruo Shimizu , Makoto Iwata","doi":"10.1016/S0168-5597(98)00039-2","DOIUrl":"10.1016/S0168-5597(98)00039-2","url":null,"abstract":"<div><p><strong>Objectives</strong>: We aimed to investigate the origin of P9 in median SEPs by applying the junctional potential theory.</p><p><strong>Methods</strong>: We studied the distribution over the body surface with contralateral shoulder reference in 4 normal subjects.</p><p><strong>Results</strong>: A stationary potential field P9/tN9 (=truncal N9) was recorded: P9 over head and neck (the smaller part), tN9 over trunk (the larger part), the boundary being located between trunk and neck. This polarity agreed with that expected from simulation studies.</p><p><strong>Conclusions</strong>: P9 is a junctional potential generated by the change of the volume conductor size between trunk and neck.</p></div>","PeriodicalId":100401,"journal":{"name":"Electroencephalography and Clinical Neurophysiology/Evoked Potentials Section","volume":"108 6","pages":"Pages 584-587"},"PeriodicalIF":0.0,"publicationDate":"1998-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0168-5597(98)00039-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20780989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}