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Ergebnisse 2 Einträge
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During the last two decades, research on interoception has experienced a surprising renaissance. New experimental approaches and methods have revealed much about the processing of afferent signals from the inner organs of the body, and have allowed more accurate descriptions of these processes, as well as a more accurate determination of their functional significance in the experience and behavior of humans. Besides neuromuscular, respiratory, and gastrointestinal interoceptive processes, the cardiovascular afferent influences are now known to be very important. Invariably, the central questions concern sensitivity to signals from the body, factors which may influence judgement of perception, and the degree to which conventional hypotheses regarding the interoceptive capabilities of humans may require revision. Findings from general psychological and clinical studies have shown that humans may attain remarkable levels of interoceptive performance. On the other hand, they also show how deep the chasm is between visceral processes and perception, and between that which is perceived and the reports thereof. Only interdisciplinary approaches to these complex processes promise success.
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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.
Erkunden
Team
- Vaitl (2)
Eintragsart
Sprache
- Englisch (2)
Thema
- Proprioception
- Adult (1)
- Autonomic Nervous System (1)
- Awareness (1)
- Cerebral Cortex (1)
- Delta Rhythm (1)
- Digestive System Physiological Phenomena (1)
- Electroencephalography (1)
- Female (1)
- Gravitation (1)
- Heart Rate (1)
- Hemodynamics (1)
- Homeostasis (1)
- Humans (2)
- Male (2)
- Neural Inhibition (1)
- Perception (2)
- Posture (1)
- Pressoreceptors (1)
- Reaction Time (1)
- Reference Values (1)
- Reflex (1)
- Reflex, Startle (1)
- Respiration (1)
- Sensory Receptor Cells (1)
- Theta Rhythm (1)
- Viscera (1)
- Visceral Afferents (1)
- Weightlessness (1)