Effects of a Warning Signal on Reactions to Aversive White Noise Stimulation: Does Warning “Short-Circuit’ Habituation?

Reduced autonomic and subjective reactions to aversive stimuli under predictable as compared to unpredictable conditions have been explained on the one hand by the mechanism of preception and on the other hand by orienting response (OR) reinstatement in the unpredictable condition, with differences in rated aversiveness not necessarily being involved. To test differential predictions based on an habituation vs. preception position, as suggested by Lykken and Tellegen, one group of male volunteers was presented with 30 trials in which the onset time of an aversive white noise tone (110dBA) was signalled, while in the other group the onset time was not signalled. A control group received unsignalled presentations of 70dBA white noise tones. Following each trial, subjects indicated the aversiveness of the white noise at its impact. SCRs were recorded continuously. Responses produced by the signalled tones decreased over trials, while responses produced by the unsignalled 110dBA tones increased over trials. The control group exhibited a continuous decrease. Self-report measures showed an overall decrease over trials but no differential decline. It was concluded that an OR reinstatement interpretation seems to be best in line with the data, although the observed functional significance of signalling at the autonomic level needs further evaluation to arrive at a clear distinction between OR theory and the preception hypothesis.     

Neurobehavioral and systemic effects of longterm blood lead-elevation in rats

In order to assess neurobehavioral deficit subsequent to early low-level lead-exposure, Wistar-rats were prenatally Pb-exposed via their mothers, neonatally via their dams' milk, and later on via their diet containing lead acetate (745 mg Pb/kg diet). Blood-lead levels (PbB) of dams increased from 24.2–31.2 g-% during pregnancy and suckling-periods, those of offsprings were 26.6 g-% at about 16 days of age and 28.5 g-% at about 190 days of age. Between 100 and 200 days of age 40 male offsprings were subjected to behavioral testing, namely an open field-test and a visual discrimination-learning task. Two learning-tasks of different complexity, i.e. orientation-and size-discrimination, were used. Data of 20 lead-treated animals were compared with those of 20 age-matched controls.In the open-field test lead-fed animals were significantly more restless than controls; an increase of ambulation, rearing and grooming was observed. In the difficult learning-task, i.e. size discrimination, only the controls did learn the problem, whereas only one of the lead-group did; there was, however, no difference between lead-and control-animals for the easy task, i.e. orientation-discrimination. The observed effects, namely overreaction in the open field and a deficit of visual discrimination learning, may be interpreted in terms of lead-induced CNS-dysfunction. They clearly suggest that the no-response level for neurobehavioral damage in the rat, subsequent to early lead-exposure, must be assumed to be lower than 35 g/100ml.Based on a paper presented at 18. Tagung experimentell arbeitender Psychologen, April 12–14, 1976, in Bochum, Federal Republic of Germany     

Differential coding of pain intensity in the human primary and secondary somatosensory cortex

The primary (SI) and secondary (SII) somatosensory cortices have been shown to participate in human pain processing. However, in humans it is unclear how SI and SII contribute to the encoding of nociceptive stimulus intensity. Using magnetoencephalography (MEG) we recorded responses in SI and SII in eight healthy humans to four different intensities of selectively nociceptive laser stimuli delivered to the dorsum of the right hand. Subjects' pain ratings correlated highly with the applied stimulus intensity. Activation of contralateral SI and bilateral SII showed a significant positive correlation with stimulus intensity. However, the type of dependence on stimulus intensity was different for SI and SII. The relation between SI activity and stimulus intensity resembled an exponential function and matched closely the subjects' pain ratings. In contrast, SII activity showed an S-shaped function with a sharp increase in amplitude only at a stimulus intensity well above pain threshold. The activation pattern of SI suggests participation of SI in the discriminative perception of pain intensity. In contrast, the all-or-none-like activation pattern of SII points against a significant contribution of SII to the sensory-discriminative aspects of pain perception. Instead, SII may subserve recognition of the noxious nature and attention toward painful stimuli.     

Fast reducers, slow augmenters: a psychophysiological analysis of temperament-related differences in reaction time.

Augmenting-reducing theory describes temperament-related differences in the modulation of stimulation. Reducers are supposed to need more stimulation than augmenters because of a cortical attenuation of incoming stimuli. The study investigated differences between augmenters and reducers (classified by questionnaire) in performance and information processing strategies in a simple reaction time task. Fifty-two subjects (27 augmenters, 25 reducers) took part in a visual reaction time task with go- and catch-trials (30%). Reaction times, commission errors, and psychophysiological indicators of information processing (N1, P300, EMG) were recorded. Reducers were faster and exhibited more commission errors than augmenters. Moreover, reducers exhibited higher N1-amplitudes, faster EMG-onsets and higher EMG-amplitudes than augmenters. An additional pain tolerance test revealed that male reducers were more pain tolerant than the other participants. These results are consistent with the proposition that reducers have a higher need for stimulation than augmenters. Probably, they utilize locomotor activity in order to compensate for their attenuated arousal.     

Dependence of Skin Conductance Reactions and Skin Resistance Reactions Upon Previous Level

When results from an earlier investigation of skin resistance reaction and skin conductance reaction taken from parallel sites were reanalyzed, a surprising discrepancy between these measures was noted. At high levels of noise stimuli (90dB and above), skin resistance reaction amplitudes decrease with the number of trials whereas skin conductance reaction amplitudes increase. This divergence can be understood in terms of level dependence of both skin conductance reaction and skin resistance reaction. Because of opposite trends in resistance and conductance level shifts in the course of the experiment, skin resistance reaction measures yield decreasing values, even if the “true” reaction were constant, whereas SCR measures tend to overestimate the reaction. After a correction based upon empirically-determined level dependence the two measures give comparable results. Theoretical considerations underlying the empirical correction procedures are discussed based upon a simple electrical model of the skin, and recommendations are made for use of AC measurement in electrodermal activity research.