Biomedical subjects

H L Fehm

Publications and source records attributed to H L Fehm.

256 records · Page 15Linked to original sources

PubMedDate not supplied

Effects of vasopressin on the habituation of the orienting reaction in men.

Effects of arginine-vasopressin (AVP) on the habituation of the orienting reaction and response to stimulus mismatch were investigated in a between-group design with 40 healthy male volunteers using skin conductance and heart rate responses as dependent measures. Twenty-one 1000 Hz tones of 90 dB(A) intensity and 2 s duration were presented with alternating intervals of 20 and 140 s. Stimulus mismatch responses were analyzed to the tones after the long intervals and to a change of the interval duration. The expected prevention of habituation as an indicator of a general stimulus-related increase of phasic arousal under AVP could not be confirmed. There were no differences between the AVP and the placebo group in the skin conductance and heart rate responses. The interval change did not provoke a dishabituation reaction, but responses to the tones after the long intervals were reliably enhanced. However, AVP did not increase the reaction to stimulus mismatch. It is concluded that autonomic indicators of the habituation of the OR remain unaffected by AVP.

Acoustic Stimulation↗

PubMedDate not supplied

Selective influence of menstrual cycle on perception of stimuli with reproductive significance.

Sixteen healthy women (20-32 years) not taking oral contraceptives were tested at three phases of their menstrual cycles (menses, preovulatory phase, and midluteal phase). Another 16 women taking oral contraceptives served as age-matched controls, and were tested during menses and during phases corresponding to the preovulatory and midluteal phase. On each test occasion, perception was assessed of visual stimuli belonging to three categories: sex (nude men), babies, and stimuli related to body care. Also, meaningless syllables were given. Stimuli were presented by a tachistoscope. Presentation of each stimulus was repeated until the subject signaled recognition. Trials to recognition and correctness of the recognition response were recorded. In spontaneously cycling women effects of the phase of the menstrual cycle depended on the stimulus meaning: During the preovulatory phase, there was an increase in the number of correctly recognized sex stimuli (p < 0.05) and of stimuli falsely recognized as sex stimuli (p < 0.05). The number of stimuli falsely recognized as body care was reduced during this phase (p < 0.05). Moreover, during the luteal phase, the number of trials to recognition of baby stimuli was diminished (p < 0.01). In women taking contraceptives, no stimulus specific changes occurred, but correct recognition was generally improved during the luteal phase. Rather than supporting a general influence of the normal menstrual cycle on perceptual functions, the present results demonstrate that the effects of the menstrual cycle depend on the meaning of the stimulus with the perception of sexual stimuli, but not of stimuli related to maternal nurture, being improved during the preovulatory phase.

Adult↗

PubMedDate not supplied

Effects of sleep on the production of cytokines in humans.

The restorative functions of sleep may affect immunologic functioning. The present study examined the effects of sleep on stimulated cytokine release in 13 healthy men. The subjects spent 2 experimental nights in the sleep laboratory. In one condition, lights were turned off at 11:00 PM to enable sleep for 3.5 hours. Thereafter, they stayed awake till 7:00 AM. In the other condition, conversely, subjects stayed awake between 11:00 PM and 3:00 AM. Then, lights were turned off for a 3.5-hour phase of sleep. Blood was sampled every 30 minutes between 11:00 PM and 7:00 AM. Sleep was monitored by polysomnographic recordings. Release of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) was determined after stimulation of mononuclear cells with lipopolysaccharide from Escherichia coli. The release of IL-2 was stimulated with phytohemagglutinin. Compared with wakefulness, after 3 hours of sleep, production of TNF-alpha and IL-1 beta was substantially diminished (p < .01). Production of IL-2 was enhanced during sleep (p < .05), with this effect being limited to the second nocturnal sleep phase after 3:00 AM. Sleep-dependent changes in stimulated cytokine release were independent of changes in plasma cortisol concentrations. These results indicate a specific reducing effect of sleep (vs. wakefulness) on cytokine production by monocytes (TNF-alpha and IL-1 beta). The rather slow development of the effects calls for further studies to establish the exact time course of the influence of sleep on cytokine production.

Adult↗

PubMedDate not supplied

Adrenocorticotropin widens the focus of attention in humans. A nonliner electroencephalographic analysis.

OBJECTIVE: This study examined the effects of ACTH 4-10, a fragment of adrenocorticotropin (ACTH) with known central nervous system (CNS) activity, on the dimensional complexity of the ongoing electroencephalographic (EEG) activity. Stressful stimuli cause ACTH to be released from the pituitary, and as a neuropeptide ACTH may concurrently exert adaptive influences on the brain's processing of these stimuli. Previous studies have indicated an impairing influence of ACTH on selective attention. METHODS: Dimensional complexity of the EEG, which indexes the brain's way of stimulus processing, was evaluated while subjects performed tasks with different attention demands. Sixteen healthy men (23 to 33 years) were tested once after placebo and another time after administration of ACTH 4-10 (1.25 mg intravenously (i.v.), 30 minutes before testing). The EEG was recorded while subjects were presented with a dichotic listening task (consisting of the concurrent presentation of tone pips to the left and right ear). Subjects either a) listened to pips in both ears (divided attention), or b) listened selectively to pips in one ear (selective attention), or c) ignored all pips. RESULTS: Dimensional complexity of the EEG was higher during divided than selective attention. ACTH significantly increased the EEG complexity during selective attention, in particular over the midfrontal cortex (Fz, Cz). CONCLUSIONS: The effects support the view of a de-focusing action of ACTH during selective attention that could serve to improve the organism's adaptation to stress stimuli.

Adrenocorticotropic Hormone↗