Heinz Zimmer

Habituation and laterality of orienting processes as reflected by slow negative waves.

The study is concerned with the question of whether the orienting wave (O-wave), a slow potential shift of the event-related brain potential, is a component of the orienting response (OR). As habituation is supposed to be the most important characteristic of the OR, we focussed particularly on any habituating aspect of the O-wave. Results suggest that its bilateral distribution over midfrontal areas might constitute such a link relating the O-wave to orienting activity. Hemispheric asymmetry linearly decreased its right-sided predominance in response to repeated presentations of an initially novel auditory stimulus. A similar, concomitant diminution of the skin conductance response (SCR) occurred. Both, the O-wave and the SCR varied, moreover, with signal value and electrodermal lability which are known to relate to the OR. Therefore we suggest the O-wave comprise features typical of a component of the OR. A hypothesis is put forward according to which the O-wave and its laterality are dependent on the ascending noradrenergic locus coeruleus system.

Psychometric properties of non-specific electrodermal response frequency for a sample of male students.

In the present study data on the frequency of non-specific electrodermal responses (NSRs) are presented for a large and, with regard to sex, age and educational level, homogeneous sample of male students (n = 590). These data were obtained in 9 independent experiments in which NSRs were recorded under equivalent conditions. NSRs were scored as skin conductance changes greater than 0.02 muSiemens. A recording period of 5 min prior to experimental manipulations was chosen. A systematic comparison between the 9 studies, the distribution of NSRs for the total sample, as well as descriptive data for stabile and labile subgroups are presented. For 213 subjects NSR-frequency was recorded twice, with a retest interval of one day. For these subjects retest analyses and data on the degree of stability of the classification into stabile and labile groups are also presented. In the discussion the necessity to develop standardized scoring criteria for NSRs is emphasized.

Stimulus rise time, intensity and the elicitation of unconditioned cardiac and electrodermal responses

In recent discussions on the differentiation of orienting, startle and defense responses, the importance of stimulus rise time for the elicitation of different cardiac response patterns was re-emphasized. Especially, it has been claimed that phasic accelerative heart rate (HR) responses-interpreted as indicators of startle-might not only be evoked by auditory stimuli with instantaneous rise times and high intensities, but also by low to moderate stimulus intensities with sudden onsets. The present study examined this question by manipulating rise time (instantaneous vs. 50 ms) and intensity (60 vs. 95 dB). Subjects (N = 120) were randomly assigned to one of the four independent groups. They performed a habituation experiment in which 12 tones of 1000 Hz with a constant interstimulus interval of 90 s were presented. On trial 13, a change in rise time was introduced by reversing the rise time condition in each group (i.e., from instantaneous to 50 ms and vice versa). Examination of HR changes across 4 poststimulus seconds, of maximal HR deceleration and acceleration, as well as examination of magnitude of skin conductance responses (SCRs) indicated clear intensity effects. Rise time, on the other hand, had no effects on HR and SC that could be interpreted as indicative of startle. Thus, it could neither be observed that instantaneous rise time led to stronger accelerative HR responses nor that the combination of instantaneous rise time and high intensity elicited anything but a dominant accelerative response pattern. These findings were also obtained when the first four trials were analyzed separately. As a consequence of stimulus change, larger SCRs as well as larger decelerative HR responses were observed without, however, being affected by the direction of the change in rise time. In sum, the present study suggests that the role attributed to rise time with respect to eliciting qualitatively different cardiac response patterns has been exaggerated. The consequences for the differentiation of different unconditioned responses are briefly addressed.

Emotional after‐effects on the P3 component of the event‐related brain potential

Agrowing body of literature indicates that affective states can influence cognitive processes. The core assumption of Ellis and Ashbrooks (1988) model explaining these emotional after-effects on cognition is that the emotional state regulates the allocation of processing resources. A negative emotional state is supposed to pre-empt capacity normally allocated to the cognitive task at hand. This is assumed to occur because the negative emotional state leads to an increase in intrusive, irrelevant thoughts, which compete with relevant cognitive activities and thus result in a lack of attention given to relevant features of the task to be performed. In the present study, the hypothesis that negative emotions lead to a reduced information-processing capacity and that this is observable on a very basic level of information processing is tested. Therefore, 102 participants were assigned to three independent groups, each inducing one of a negative, a positive, or a neutral mood by means of a 3-minute video-clip. Shortly after the video-clip, two acoustical stimuli with increasing information were presented, while the P3 component of the event-related brain potential on these stimuli was measured as a psychophysiological indicator of cognitive resource allocation. In addition, the expenmental manipulation was checked by assessing subjective and external mood ratings as well as cortical alpha activity. Results show that the videos did in fact induce positive, neutral, or negative mood. Moreover, even when controlling for video-related unspecific cortical arousal, a significant emotional after-effect was found on the P3 component of the event-related brain potential, indicating reduced information-processing capacity, particularly in the negative mood condition. The reported data support Ellis and Ashbrooks model of emotional after-effects on cognitive processes. As those effects were observable after an event that did not demand a high amount of cognitive resources, this suggests that even tasks that do not heavily engage central processing resources and are not likely to be influenced by cognitive strategies, seem to be affected by a negative emotional state.

Habituation and recovery of a slow negative wave of the event-related brain potential.

This study is concerned with the question of whether the late, slow negative wave 2 (SNW2) component of the event-related brain potential is a component of the orienting response (OR). As habituation of the SNW2 would be an argument for such a link with the OR, it was investigated using a variant of the classical repetition/change paradigm. Results supported major claims to be made for a component of the OR: the amplitude of the vertex SNW2 exhibited roughly the typical exponential decline with repeated stimulations (six numeric verbal stimuli presented seriatim in an ascending order) and responded incrementally to a change, at least in a narrow time slot, i.e. it exhibited partial recovery to an out-of-sequence stimulus. These findings were accompanied by similar effects on an exemplary OR component, the skin conductance response, and on such possible components of the OR as heart rate deceleration and the vertex P3 of the event-related brain potential. In so far as OR components should behave in comparable fashion in response to orienting stimuli, it is thus reasonable to suppose that the SNW2 relates to the OR.

Frequenz und mittlere Amplitude spontaner elektrodermaler Fluktuationen sind keine austauschbaren Indikatoren psychischer Prozesse

Zusammenfassung. Die Arbeit ging experimentell der Frage nach, ob zwei zentrale Aspekte spontaner elektrodermaler Fluktuationen, ihre Frequenz und ihre mittlere Amplitude, dieselbe Information uber psychische Prozesse liefern. Experimentell variiert wurde dazu mittels Imaginationsmethode das Thema und der Selbstbezug induzierter Vorstellungen. Die experimentellen Manipulationen folgten einem 2×2-faktoriellen Versuchsplan fur unabhangige Gruppen (Zellbesetzung: jeweils 24 Personen). Gemessen wurde die Veranderung der elektrodermalen Aktivitat von einer Ruhe- zu der Vorstellungsphase. Die Ergebnisse zeigten, das die beiden Variablen keine austauschbaren Indikatoren psychischer Prozesse sind. Trotz eines substantiellen korrelativen Zusammenhangs reagierten sie sehr eigen auf die experimentellen Manipulationen. Die Variation der Vorstellungsthematik wirkte nur auf die Frequenz, die Variation des Selbstbezugs der Vorstellungen nur auf die mittlere Amplitude der spontanen elektrodermalen Fluktuationen. Die beid...