E. Groll-Knapp

Occurrence of infraslow potential oscillations in relation to task, ability to concentrate and intelligence

The occurrence of infraslow potential oscillations (ISPOs) of the brain was investigated during a listening and a resting condition in 44 subjects (Ss) with high (HAC) and low ability to concentrate (LAC). The occurrence of ISPOs was found in 36% of the Ss. While in the HAC group the occurrence of ISPOs did not change from listening to resting, in the LAC group Ss with ISPOs were affected by experimental conditions, showing ISPOs during the listening condition. For Ss with ISPOs only during listening a lower score was found for ability to concentrate, suggesting ISPOs as a possible underlying mechanism. For Ss with stable ISPOs a higher I.Q. was found compared to Ss without ISPOs.

Changes in discrimination learning and brain activity (ERP's) due to combined exposure to NO and CO in rats☆

Carbon monoxide (CO) and nitric oxide (NO) are air pollutants frequently appearing in combination. Information available on the mechanisms of NO intoxication suggests that in mixtures with CO additive effects should be assumed. In this study CO and NO-induced changes and their interaction were investigated at different levels of integration: carboxyhemoglobin (COHb) and methemoglobin (met-Hb) formation as well as centrally mediated effects were analyzed using evoked potential techniques and behavioral data from a complex discrimination learning experiment. Slight enhancements of COHb and met-Hb concentrations were seen for the combined CO + NO exposure conditions at low and high exposure levels when compared to isolated exposure conditions. The performance decrease was clearly higher under NO exposure than under CO exposure. Decrements were overadditive when simultaneous CO + NO exposure was used in higher concentration. Both gases affected early evoked potential components (P10, N30) in the same way: latencies were prolonged and amplitudes increased. Later potential components were differently influenced by CO and NO. Mainly the N150 amplitude was decreased in NO exposure and increased in CO conditions. N150 amplitude was also decreased after combined CO + NO exposure. At high levels this effect was overadditive indicating a dominant role of NO in the CO + NO combinations used in this experiment.

Different storage methods for biopotential skin electrodes (sintermetallic Ag/AgCl) and their influence on the bias potential

SummaryThe aim of the present study was to investigate the influence of various methods of storage on the Differences in Electrode Potential (DEP). For periods of 22 h each, 10 Ag/AgCl sintered metal biopotential skin electrodes were stored in 4 media: “dry”, in a 0.9% NaCl solution, in distilled water and in electrode jellies. When storing the electrodes in 0.9% NaCl, distilled water, and electrode jelly all the electrodes of one make were stored together in a container filled with the medium in question, with and without the application of an external short circuit. After storage the electrodes were filled with one of 3 electrode jellies (Beckman Electrode Electrolyte, Parker Spectra 360, Siemens Electrode Gel). The DEPs between each two electrodes were measured 10, 30, 60 and 120 min after filling. The results show no difference for the two makes of electrodes (Beckman and IVM), but clear differences (up to factor 50) were observed in the electrode jellies used. The method of storage has a significant influence on the DEP. Dry storage yielded the lowest values (p<0.001) for all electrodes and electrode jellies (x between 84 and 318 ΜV) and the highest stability. When stored in 0.9% NaCl, distilled water and electrode jelly, both with and without external short circuit, the electrodes showed DEPs in the mV range and drifted strongly during the period of observation, except after short-circuited storage in 0.9% NaCl, when a phase of stability is reached after 60 min.

Cortical DC-Shifts Related to Sustained Sensory Stimulation and Motor Activity

On the question of event-related slow (DC) potentials in the brain, Haider et al. (1981) published a review paper some years ago. Since that time our group has tried to deal with brain DC shift related to longer term information processing and motor activity. This is of course only possible with the use of special DC electrodes and special DC amplification systems.

Interactions between noise and air pollution

Abstract A theoretical framework for the discussion of interaction effects between noise and air pollutants (e.g., carbon monoxide, heavy metals, and organic solvents) on the auditory system as well as on extraaural systems is presented. The interactions are categorised into five groups: local interaction, independent action, dependent aftereffects, transaction, and general interaction. Information on combined effects of carbon monoxide and noise, as well as carbon monoxide and nitrogen oxide, serve as examples how the different intensities of effects, as well as the different effect levels, may be taken into account within the described theoretical framework. The problem of sensory interactions as well as combined annoyance effects are analysed with the same conceptual approach.

Combined effects of mental load and background noise on CNS activity indicated by brain DC potentials

Abstract To assess combined effects of noise and mental load on brain activity, DC potential shifts were evaluated. In a 4-way repeated analysis of variance (ANOVA) design with Type of Noise, Sound Intensity, Mental Load, DC Recording Location as factor, 2-min epochs of noise exposure were compared in 18 subjects. Significant main effects were found for Type of Noise (white noise and street noise showing greater positive shifts than music sound), Mental Load (more positive shifts for mental load vs. no mental load), and DC Recording Location. Statistically significantly higher order interaction effects were also found. Low intensity of music sound diminished the mental load CNS activity (DC shifts), interpreted as a possible compensatory effect of soft music on mental load. The effect of mental load under street noise and white noise conditions depends on the CNS activity (DC shifts) caused by these background noises alone, showing a ceiling effect. Results indicate that CNS activity (DC shifts) apparent during mental load are changed by acoustic stimulation additionally applied and that this effect is dependent on type of noise/sound and sound intensity.

The electromyographic DC potential as a correlate of muscular activity

SummaryThe present experiment was undertaken to demonstrate the effect of muscular force as well as duration of muscular work on the electromyographic (EMG) DC potential. Thirty subjects had to lift different weights by flexing the right forearm within a defined and constant setting for 20 s. The experimental variables were weight (0.5, 1, 2, and 3 kg) and time. The EMG was recorded from the belly of the right biceps brachii muscle in a quasi-unipolar manner and split into an integrated ac channel (IEMG) and a dc channel (DC-EMG). The average IEMG showed a ramp-like shape. Analysis showed a positive relationship for weight (p<0.0001) and time (p<0.0001) with the IEMG. The average shape of the DC-EMG showed a negative initiation potential, a monotonically increasing negative potential during contraction (contraction potential), a positively peaking off potential and a slow return to baseline (after potential). Analyses of variance demonstrated a significant (p<0.001) relationship of weight to the magnitude of the initiation and the termination potential. Regression analyses displayed an inverse relationship of time to the termination (p<0.01) and to the resolution potential (p<0.001). The DC-EMG showed higher peaks (initiation and termination potential) for heavier weights. For the termination and after potential less positive deflections were found with increasing time (fatigue). A control condition (isometric contraction) indicated that the initiation, contraction, and termination potential of the DC-EMG may also be related to aspects of the movement. Results suggest that the DC-EMG is a more complex measure of muscular activity than the IEMG.

Auditory evoked potentials from cortex and various subcortical centers

SummaryThe auditory system possesses connections to many different levels of the central nervous system.To secure some information that might be fitted into a future model, providing a better understanding of the underlying phenomena, AEP were recorded from the scalp, various cortical fields, and various subcortical structures during stereotaxic neurosurgical interventions.There is no doubt that vertex-mastoid registrations reveal non-specific components of the AEP, which can also be detected in recordings from subcortical structures.Latencies differed widely between responses obtained from the various structures, the shortest being that from the medial geniculate body.The authors further discussed the thalamo-cortical relationship of the CNV.ZusammenfassungDas Hörsystem ist eines der wichtigsten Sinnessysteme. Es ermöglicht durch seine zahlreichen Verbindungen zu allen funktionellen Niveaus des Zentralnervensystems einschließlich des Rückenmarks die kürzeste Reaktionszeit auf einen Sinnesreiz. Der „Sonomotorreflex” spielt mit eine Rolle, indem er die Muskulatur über das schnelle γ1-System in Bereitschaft versetzt.Phylogenetisch und entwicklungsgeschichtlich wird die Bedeutung des akustischen Systems durch die Tatsache unterstrichen, daß es für Tiere in freier Wildbahn die wichtigste Warneinrichtung darstellt.Der Versuch, unspezifische, akustisch evozierte Potentiale (AEP) bei Skalpableitung als myogenen Artefakt abzutun, führte zur Entdeckung des Sonomotorreflexes und zu der Erkenntnis, daß eine schnelle myogene Komponente von der langsameren cerebralen in der Vertex-Mastoid-Ableitung unterschieden werden muß.Um einen Beitrag zur Elektrophysiologie des akustischen Systems zu leisten, wurde begonnen AEP mit Subperiostalnadelelektroden, mit durch das stereotaktische Bohrloch eingeführten flexiblen AgAgCI-Cortexelektroden von verschiedenen Rindenfeldern, und mit Tiefenelektroden von vielen thalamischen Kernen (einschließlich des Geniculatum mediale) und verschiedenen anderen subcorticalen Strukturen (Ammonshorn-Mandelkern-Komplex, Fornix, vordere Commissur) abzuleiten. Solche Gelegenheiten bieten sich bei den elektrophysiologischen Kontrollen während stereotaktischer Hirnoperationen am Menschen. Voraussetzung ist eine moderne elektronische Ausrüstung.Die Latenzen der unspezifischen Komponenten der AEP in den verschiedenen Strukturen sind sehr unterschiedlich. Auch die Form variiert über verschiedenen Rindenfeldern, läßt aber bei entsprechender Verstärkung Gemeinsamkeiten mit den vom Vertex-Mastoid abgeleiteten AEP erkennen.Die im Geniculatum mediale erstmals am Menschen bestimmte Latenz des Deflexionsbeginnes des spezifischen AEP beträgt etwa 7 msec.Es werden auch Untersuchungen der thalamo-corticalen Beziehungen der Erwartungswelle oder der kontingenten negativen Variation, sowie des motorischen Bereitschaftspotentials oder der Intentionswelle vorgenommen, wobei paarweise Clicks in irregulären Intervallen angewandt werden.Auf die mögliche Bedeutung des ersteren Phänomens für eine eventuelle objektive Sprachaudiometrie wird hingewiesen.

Perception of species-specific vocalizations in rats : role of the cholinergic septo-hippocampal pathway and aging

The effect of a chemical lesion of the cholinergic septo‐hippocampal pathway induced by ethylcholine aziridinium (AF64A) on brain potentials evoked by species‐specific vocalization containing informations of high biological relevance was studied in young adult (10 months) and aged (24 months) rats by means of neocortical electroencephalographic recordings. In control rats, the perception of a rats vocalization in a life endangering situation (lasting 0.8 s) initiated an evoked potential followed by a late positive slow wave (LPSW)‐complex and a direct current shift with a duration of up to 16 s. Four months after treatment with AF64A (2 nmol into each of the lateral ventricles), the main negative component of the initial acoustic evoked potential (peak latency of about 60 ms after stimulus onset) was reduced (P = 0.04) both in young adult and aged rats. Further changes included a decrease of the late positive wave amplitude in young adult rats (P = 0.001) and a shorter duration of the LPSW‐complex in aged rats (P = 0.03). AF64A induced also changes in specific components revealed by Principle Component Analysis, but only in the group of young rats. A decrease in the slow wave component (factor 1, 3000–4000 ms after stimulus onset ; P = 0.02) was observed. Age per se affected the late positive potential shifts as indicated by a shorter latency of the late positive wave (P = 0.03).