Working with new technologies: hormone excretion as an indicator for sustained arousal. A pilot study.

Effects of working with new technologies (visual display units) on hormone levels were investigated in a pilot study. The relationship between subjective strain and hormone levels was also assessed. Twenty subjects participated in the study reported here, which is a part of a comprehensive longitudinal study, in which 279 employees participated. Measurements were taken two months before the new technology was installed (baseline: work with conventional technology), during the implementation phase of the new technology, and at a 12-month interval. Fourteen complete data sets were analysed. The introduction of new technologies was accompanied by enhanced levels of catecholamines (epinephrine and norepinephrine). Levels also remained high one year after the implementation. Similar values were found on work days and rest days. Cortisol changes were less evident; excretion tended to increase after the implementation had been completed. The relationship was weak between hormone levels and subjective strain measurements. The results indicate that working with new technologies was accompanied by enhanced physiological arousal of the employee. Reactivity was related more to a particular occupational setting than to scales of subjective assessment.

The 'oddball CNV' as an indicator of different information processing in patients with panic disorders.

In previous studies we found an inverse relationship between CNV amplitude and the probability of the occurrence of the warning stimulus (S1) in a cued reaction time task. The aim of the present study was to investigate this 'oddball effect' on CNV amplitude (Oddball CNV) in patients with anxiety disorders, since this effect describes the influence of event probability on reactive as well as proactive components of information processing. Patients suffering from panic disorders with or without agoraphobia and controls participated in a choice reaction time experiment. The subjects' task was to respond to flashes (S2s), cued 4 s in advance in random order by one of two easily distinguishable acoustic stimuli (S1a, S1b). In condition 1 the probability of S1a and S1b was 0.2 and 0.8, respectively, and in condition 2 0.5 for both S1s. The DC-EEG was recorded from F3, F4, C3, Cz, C4 and P3, linked mastoids as the reference. The data obtained confirm the oddball effect on the CNV amplitude, show clear deviations of patients in this effect, and also indicate remarkable differences in CNV shape between patients and controls. These observations are discussed as differences in information processing and information utilization.

Rare events and the CNV--the oddball CNV.

Event-related brain potentials (ERPs), such as Nd and P300, change as a function of the proportion of time if a rare, significant, stimulus occurs. This 'oddball' paradigm has had a significant influence on the interpretation of ERPs in terms of the psychological and information-processing functions they reflect. Interpretations of transient components have differed considerably from that of the sustained potential known as the Contingent negative Variation (CNV), the latter appearing to reflect proactive rather than reactive brain processes. However, experiments in monkeys indicated that the CNV was also sensitive to the oddball effect. The purpose of this experiment was to replicate that finding in humans. The CNVs and P300s of five male and five female college students were studied under three conditions involving different proportions of two types of warning stimuli in a cued reaction time task (paired tone and light). The proportions of one of the warning stimuli, with respect to the total number of trials, were 0.10, 0.30 and 0.50. P300s were larger when elicited by rare warning tones only in the 0.10 condition with maximum P300 amplitude at the parietal site. CNVs at frontal and central areas were larger when the warning cue was the rare event, but there was no effect at the parietal site. These findings may require a rethinking of specific information processing interpretations of other endogenous ERPs, although the results also indicate that the 'oddball' effect on the P300 and CNV was distinctive in terms of scalp distributions and sensitivity to the manipulation.

[The anticipatory potential (contingent negative variation) as an indicator of neuronal information processing in relation to changes in slow potentials in the EEG]. / Die Erwartungswelle (CNV) als Indikator neuronaler Informationsverarbeitung in Abhängigkeit von spontanen Gleichspannungsänderungen im EEG.

The aim of this study was to investigate the interaction between spontaneous Slow Potential Shifts (SPSs) and the probability effect on CNV amplitudes. Fifteen right-handed volunteers participated in this experiment. The presentation of the stimuli was triggered by spontaneous SPSs (duration: 2 seconds, mean-amplitude: 10 microV) in the EEG signal at Cz. Thus, two different S1s (S1a: 1500 Hz, S1b: 2000 Hz) were presented in a random order with a fixed probability of occurrence of 0.8 for S1a and 0.2 for S1b. Each S1 was followed by a light stimulus (S2) with a constant ISI of 4 seconds. According to the cue, the subjects had to push the left (S1a) or the right (S1b) response button as fast as possible with their right index finger. The order of the 4 experimental conditions (stimulus presentation triggered by negative or positive shifts and recording of negative or positive shifts without any stimuli) in which each subject participated was balanced across subjects. Several significant effects could be found by means of a two-way ANOVA for repeated measures (condition x recording site): Negative shifts were accompanied by smaller CNVs as well as PINVs (resolution deficits) at all recording sites; the probability effect was found to be significant in the positive shift condition at F3, F4, and Cz, but not in the negative shift condition except at Cz for the E-wave. CNVs triggered by negative shifts only showed a significant correlation (-.55) with reaction time. These results together favor a two-component model suggesting that SPSs, spontaneous and evoked, are largely generated by glia depolarization, which is evoked by but outlasts neuronal activity.

Technical requirements for high-quality scalp DC recordings.

An easily applicable procedure for obtaining high-quality scalp DC recordings is described. A sophisticated amplifier technique, skin potential reduction and stabilisation of electrode potential make up this procedure.