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An experiment with 42 human Ss used the transswitching procedure to examine tonic stimulus control of phasic and tonic conditioned vasomotor heart rate, and electrodermal reactions. The conditional stimulus (CSs) were photos of angry and friendly human faces, and the unconditional stimulus (US) was a human scream. In one tonic context (blue light), the CSs were paired with the US, in the other context (yellow light), the CSs were presented unpaired. Following acquisition, an extinction series was run with the US omitted during both tonic contexts. Phasic vasomotor and skin conductance reactions differed in the positive and negative tonic segments (stronger in positive). The skin conductance responses also differed during extinction, but the vasomotor responses did not. Tonic differences (following onset of the tonic stimuli) in unelicited skin conductance response frequency, finger pulse volume, and heart rate were also found, although these developed more slowly than the phasic differences. The finger pulse volume tonic difference was greater in extinction than the skin conductance response frequency. There was no effect of the angry-friendly facial expressions, either directly or in interaction with the transswitching effects. The results were interpreted to mean that the transswitching phenomenon is not limited to one another autonomic effector, but is more generalized across the ANS (sympathetic branch). The absence of influence of the facial expressions indicates the relative weakness of the "preparedness" hypothesis in comparison with more influential contextual factors.
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The present study was carried out to determine the inhibitory cortical processes induced by changes in hemodynamics. Previous experiments in humans conducted in our laboratory have shown that there is a close relationship between posture and delta and theta EEG activity. The most pronounced effects were obtained during the 6 degrees head-down tilt (HDT) position. In space medicine the HDT procedure is very frequently employed to simulate micro-gravity and to determine the neurohormonal counter-regulations evoked by the expansion of central volume. Twenty male subjects spent 23 h in bed in 6 degrees HDT and 23 h in 6 degrees HUT (head-up tilt) positions during which EEG (frontal, central, parietal, occipital), startle responses, and reaction-times were measured every 2 h (from 10:00 h till 20:00 h). The effects of cardiovascular deconditioning (CD) regularly occurring after HDT were assessed by examining orthostatic tolerance and the physical work capacity (bicycle ergometry). As expected, 23 h HDT led to more pronounced CD than HUT. Spectral power analyses of EEG revealed increases in delta and theta frequency hands similar to those found during HDT in previous EEG studies. In addition, subjects responded more slowly (S1-S2 reaction-time task) during HDT as compared with HUT bedrest. The influence of HDT on startle response, however, was not in keeping with the initial hypothesis (i.e. dampening of reflex activity). The EEG data and the sensorimotor performance indicated that the body fluid shift towards the thoracic cavity induced by HDT resulted in signs of cortical inhibition. In addition to neural mechanisms, other processes must be postulated which are closely related to the counter-regulation evoked by the varying body positions.
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Eintragsart
- Buchteil (1)
- Zeitschriftenartikel (3)
Thema
- Adult (3)
- Anger (1)
- Arousal (1)
- Biofeedback, Psychology (1)
- Cerebral Cortex (1)
- Conditioning, Psychological (1)
- Delta Rhythm (1)
- Electrocardiography (1)
- Electroencephalography (1)
- Extinction, Psychological (1)
- Facial Expression (1)
- Female (2)
- Gravitation (1)
- Habituation, Psychophysiologic (1)
- Heart Rate (2)
- Hemodynamics (1)
- Homeostasis (1)
- Humans (3)
- Male (3)
- Neural Inhibition (1)
- Perception (1)
- Posture (1)
- Pressoreceptors (1)
- Proprioception (1)
- Reaction Time (1)
- Reference Values (1)
- Reflex (1)
- Reflex, Startle (1)
- Respiration (1)
- Skin (1)
- Smiling (1)
- Theta Rhythm (1)
- Vasoconstriction (1)
- Weightlessness (1)