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At least 19 recordsLinked to original sources
PubMed1976

A comparison of direct blood pressure feedback and electromyographic feedback on the blood pressure of normotensives.

Groups of 20 normotensive subjects were assigned to one of three conditions to help them lower their blood pressure: (1) intermittent visual feedback of blood pressure; (2) continuous analogue auditory feedback of frontal EMG; (3) an instructed, no-feedback condition. Both groups receiving feedback showed greater within-session lowering of systolic blood pressure than the no-feedback control group. Although the group receiving intermittent visual feedback of blood pressure lowered blood pressure more than the EMG feedback group at the first session, in three subsequent sessions, the two feedback groups did not differ.

Adolescent↗
PubMed1976

Experimental studies on the positive feedback effect of progesterone, 17 alpha-hydroxyprogesterone and 20 alpha-dihydroprogesterone on the pituitary release of LH and FSH in the human female. The estrogen priming of the progesterone feedback on pituitary gonadotropins in the eugonadal woman.

Administration of progesterone eugonadal women during the midfollicular phase of the menstrual cycle failed to induce a positive feedback effect on the serum concentrations of LH and FSH. The levels of estradiol in serum decreased following the injection of progesterone without a parallel change in LH and FSH concentrations indicating a direct ovarian effect of the exogenous progesterone. In the late follicular phase of the cycle, when preovulatory levels of estradiol were present in serum, or under a ethinyl estradiol treatment progesterone was able to induce an LH discharge indicating the requirement of an estradiol priming of the positive feedback of progesterone in eugonadal women. In order to establish the time required for a sufficient estrogen priming with preovulatory levels of estradiol in serum 3 mg of estradiol-benzoate were administered i.m. 1, 12 and 24 h prior to the administration of 30 mg of microcristalline progesterone in the midfollicular phase of the menstrual cycle, when progesterone alone did not cause an LH surge. Only when estradiol-benzoate was injected 24 h prior to the progesterone administration an LH surge reproducible in time course and magnitude occurred. Administration of estradiol-benzoate alone under these conditions did not cause an LH surge within the elapse of time after the injection when the progesterone induced LH surge occurred. Thus, these experiments demonstrate that a defined estrogen priming is required for the positive feedback effect of progesterone on the gonadotropin release in eugonadal women. Furthermore, progesterone levels in serum of about only 1--2 ng/ml were required for the induction of an LH surge indicating that under physiological conditions progesterone may have an supplementory effect on the primarily estradiol induced LH midcycle peak. 17-hydroxyprogesterone administered during the mid follicular phase of the menstrual cycle and under pretreatment with ethinyl estradiol failed to induce a positive feedback effect on the serum concentrations of LH and FSH, indicating that this steroid does not play a regulatory role on the midcycle LH release in women. 20alpha-dihydroprogesterone administered under the same experimental conditions as 17-hydroxyprogesterone seems to be able to induce an LH surge in serum provided there is an adequate estrogen priming.

20-alpha-Dihydroprogesterone↗
PubMed1979

Effect of information feedback on temporal discrimination in concurrent and post-feedback measures.

College students estimated time intervals (5, 6, 7, 8, and 9 sec.) where one group (N = 20) received information feedback in terms of actual interval durations and a second group (N = 18) received no information. Theshold measures were then taken for all subjects using the method of constant stimuli (comparison stimuli of 5, 6, 7, 8, and 9 sec. and a 7-sec. standard). In addition to increased accuracy and consistency of judgments, the feedback group showed a decreasing Weber fraction during the estimation phase, while the Weber fraction for the no-feedback group increased. The feedback group retained only a slight advantage in subsequent threshold measures; group differences in difference thresholds and derived nonparametric estimates of d' were nonsignificant.

Differential Threshold↗
PubMed1975

[Studies on circadian rhythm and the feedback mechanism of hormone secretion from the hypothalamic-pituitary-adrenal system --pertaining to the circadian variation of feedback sensitivity in the hypothalamic-pituitary axis-- (author's transl)].

In order to investigate the relationship if any between the circadian rhythm of the hypothalamic-pituitary-adrenal system and of feedback sensitivity in the hypothalamic-pituitary axis, temporal changes of serum corticoid level and of ACTH responsiveness to metyrapone were studied in 5 controls, 4 patients with loss of consciousness due to central nervous system diseases (Group A), 2 blind subjects (Group B) and 2 patients with psychiatric disorders accompanied with sleep-wake cycle disturbance (Group C). Two patients in Group A with normal circadian rhythm of serum corticoid levels exhibited abnormal rhythm in ACTH responsiveness to metyrapone. In contrast, 2 other patients in Group A with normal rhythm in ACTH responsiveness to metyrapone exhibited abnormal circadian rhythms of serum corticoid levels. In spite of the disturbed circadian rhythm of serum corticoid levels, 2 patients in Group B showed normal rhythm in ACTH responsiveness to metyrapone. Two patients in Group C exhibited abnormalities in both circadian changes. It was concluded that there might be different control mechanisms between the circadian rhythmicity of the hypothalamic-pituitary-adrenal system and of the feedback sensitivity.

Adrenal Cortex Hormones↗
PubMed1978

Overproduction disease in man due to enzyme feedback resistance mutation. Purine overproduction in gout due to excessive activity of mutant feedback-resistant phosphoribosylpyrophosphate synthetase.

Physiologically superactive phosphoribosylpyrophosphate (PRPP) synthetase, due to feedback resistance mutation, was found in a family with excessive purine production, gout and uric acid lithiasis. The superactivity of the mutant enzyme was manifest in the propositus' erythrocytes and cultured fibroblasts, in increased generation, content and metabolic availability of PRPP, leading in the fibroblasts to acceleration of the rate of purine synthesis de novo. One of the propositus' two siblings was similarly affected, but the propositus' father, his second brother and four sons, were all clinically and biochemically normal. The mother was clinically normal and normouricemic, but hyperuricosuric. Cultured fibroblasts from her skin exhibited variability in PRPP content and availability and in the rate of purine synthesis de novo. The mother's cultures were found to contain a mosaicism of two cell populations, one with normal and the other with mutant PRPP synthetase, indicating an X-linked pattern of inheritance of the PRPP synthetase abnormality in this gouty family.

Adolescent↗
PubMed1976

Feedback-aided self-regulation of skin temperature with a single feedback locus. I. Acquisition and reversal training.

A technique has been developed that enables most humans to establish rapid self-regulatory control of their own skin temperature when provided with immediate visual feedback information concerning variations in local skin temperature. Training took place during 15-min periods within 45-min sessions. Clear evidence of learning was usually manifested within 4 sessions. After acquisition occurred, mean change per session was approximately 2.2 degrees F, ranging up to 6.5 degrees F. Training was continued with some subjects who were taught to alter temperature in opposite directions during successive periods on the same day. After practice, these subjects routinely displayed ranges of 9-14 degrees F within 15 min.

Adolescent↗
PubMed1976

Effects of positive and negative feedback on behavior control in hyperactive and normal boys.

The hypothesis that hyperactive boys have relatively less response to negative feedback than to positive feedback was studied. Sixteen hyperactive boys and 16 controls were compared on two tasks under different feedback conditions. Feedback conditions were no feedback, positive feedback, and negative feedback. Tasks were symbol encoding and correcting spelling words. Hyperactives and controls were compared in amount of time on-task and amount of work correctly completed. Hyperactives were on-task significantly more under conditions of negative feedback than under positive feedback, but negative feedback significantly increased errors on the spelling correction task. Controls were equally responsive to positive, negative, or no feedback. Hyperactives accomplished significantly less than controls on the coding task, but performed as well as controls on the spelling correction task, which was administered to each boy at his own level of spelling ability. The results imply that while consistent negative feedback can reduce off-task behavior for hyperactives, it can also decrease the accuracy of the work they are doing.

Behavior Therapy↗
PubMed1976

On the self-regulation of the occipital alpha rhythm: control strategies, states of consciousness, and the role of physiological feedback.

In an experiment investigating the self-control of occipital alpha strength, a factorial design was employed with two levels of feedback (available or non-available), three levels of instruction (Cognitive, Oculomotor, and none), and two levels of lighting (on and off), except that the no-feedback-no-instruction group was not run. The Cognitive instructions were based on the strategies reported in the literature: To generate alpha, persons were instructed to relax, "let go", try to feel pleasant and serene, and allow themselves to review pleasant personal experiences; to suppress alpha, persons were instructed to concentrate, try hard, exert themselves mentally, and try to fell anxious or frustrated. The Oculomotor instructions to generate alpha were to visually blur and not focus, and to suppress alpha were to "look" and focus. The results led to the following conclusions: (a) Feedback-augmented enhancement and suppression of occipital alpha strength is always mediated by learned control of oculomotor processes, although sometimes persons are not aware that they are employing this strategy, especially in the case of alpha enhancement; alpha feedback trainees learn to "not look" in order to enhance alpha strength. (b) Whenever Cognitive strategies are successful in producing alpha strength changes, this is due to the fact that they can be efficient mediators of changes in oculomotor processes. (c) Feedback together with simple Oculomotor instructions leads to more successful alpha control than either alone. (d) High or enhanced levels of occipital alpha strength are not invariably accompanied by the "alpha experience", in fact, if a person is not led to expect it, the alpha experience will usually not occur during occipital alpha enhancement feedback. (e) States of nonsensory awareness, such as an absorption in thoughts and feelings, are reliably associated with enhanced occipital alpha strength. This association is what would be expected: Since vision is the dominant sensory modality in humans, it is reasonable that when visual processing is reduced during alpha enhancement feedback that there is also reduced sensory awareness in general and often greater attention to thoughts and feelings. (f) Alpha feedback per se is neither necessary for nor especially facilitative of the achievement of the alpha experience. Thus, if the alpha experience is more likely to occur with alpha feedback than without it, this is due to the special circumstances that make up the feedback situation and not due to alpha feedback per se.

Alpha Rhythm↗
PubMed1977

Dynamics and mechanics of corticosteroid feedback at the hypothalamus and anterior pituitary gland.

Corticosteroid feedback mechanisms were investigated at the hypothalamic level using the rat hypothalamus in vitro and the pituitary level using basal hypthalamic-lesioned rats. Both fast and delayed corticosteroid feedback effects were demonstrated at the level of the hypothalamus and pituitary gland with doses of corticosteroids within or near the physiological range. These two phases of feedback were separated temporally by a 'silent period' during which no feedback was apparent. Studies on the mechanism of action of corticosteroids at the hypothalamic level showed that the fast feedback mechanism acts by inhibition of release whilst the delayed feedback mechanism acts by inhibition of both synthesis and release. The fast feedback action of corticosterone does not appear to act by excitation of neuroinhibitory pathways since neither picrotoxin nor phentolamine prevented the feedback action of corticosteroids in vitro. Corticosterone inhibition of corticotrophin releasing factor release was overcome by depolarization of the membrane with K+ suggesting that the mechanism of action of the fast feedback of corticosteroids is by membrane stabilization.

Acetylcholine↗
PubMed1976

Acute and reversible inhibition of tubuloglomerular feedback mediated afferent vasoconstriction by the calcium-antagonist verapamil.

UNLABELLED: In order to analyze the role of afferent vasomotor activity in mediating tubuloglomerular feedback response, we studied the effect of the intravenously applied Ca++ antagonist Verapamil on proximal stop flow pressure (SFP). In Wistar rats SFP was recorded continuously upstream of a solid paraffin block under either zero or 50 nl/min loop perfusion rate with artificial tubular fluid. The latter elicits maximal feedback response. Similar experiments were performed on heminephrectomized rats which are known to exhibit a highly sensitive feedback response. RESULTS: Verapamil given as a single dose (0.05-0.15 mg/kg b.w., i.v.) resulted in a transient decrease of mean arterial blood pressure of about 10 to 20 mmHg (1 to 3 min), SFP was unaltered during zero loop perfusion. Verapamil applied during a feedback stimulated SFP decrease (50 nl/min loop perfusion) caused restoration of normal SFP for 6 to 10 min indicating an acute and reversible interference of this drug with feedback regulation. Reversal of feedback response was complete in both groups of rats irrespective of the large difference in their feedback sensitivity. Thus: 1. The Ca++ antagonist is a complete inhibitor of feedback mediated SFP changes, 2. decreased SFP during high loop perfusion rate could be titrated back to normal by continuous infusion of Verapamil (dose 0.04 mg/kg-min), 3. Furthermore, feedback regulation of SFP could be prevented by infusion of the drug just prior to increasing loop perfusion rate.

Animals↗
PubMed2021

Comprehension of skin cancer genetic risk feedback in primary care patients.

Few studies have examined comprehension and miscomprehension of genetic risk feedback for moderate-risk genes in the general population. We examined the prevalence and nature of accurate and inaccurate genetic risk feedback comprehension among those who received genetic testing for melanocortin-1-receptor (MC1R) gene variants that confer moderate melanoma risk. Participants (N = 145 Albuquerque, NM) were tested as part of a randomized controlled trial. Two weeks after receiving MC1R genetic risk feedback, participants answered open-ended questions regarding their reactions to the MC1R feedback report. Participants' comprehension of their feedback (average-risk or higher-risk for melanoma) was evaluated through qualitative analysis of open-ended responses. Most participants demonstrated comprehension of their feedback results (i.e., 63% of average-risk participants [ARPs]; 51% of higher-risk participants [HRPs]). Miscomprehension was evident in fewer participants (i.e., 16% of ARPs, 11% of HRPs). A few ARPs misunderstood the purpose of testing, whereas a few HRPs reported confusion about the meaning of their risk feedback. Some participants' responses to the open-ended questions were too ambiguous to ascertain comprehension or miscomprehension (i.e., 21% of ARPs, 38% of HRPs). Taken together, these findings suggest that genetic testing feedback for MC1R risk variants is largely comprehensible to general population participants. This study adds to the work examining comprehension and usage of common, moderate risk genetic information in public health contexts. However, to maximize the utility of genetic risk information in the general population, further research is needed to investigate and address areas where common genetic risk feedback misunderstandings occur.

Genetic testing↗
PubMed1979

The use of visual feedback to control vocal intensity and nasalization.

A device which provides visual feedback of vocal intensity, nasalization, or a ratio of nasalization to vocal intensity, is described. The device was used in several experiments in which control of vocal intensity was a necessary component. Normal and hypernasal speakers were able to control their vocal intensities successfully when using the visual display. The display also was used in an experiment designed to determine how well normal speakers can manipulate their nasalization without visual feedback and whether they improve when feedback is provided. Subjects manipulated their nasalization first without feedback, then with feedback, then, again, without feedback. The subjects' performance improved when feedback was provided and determined when feedback was removed. It appears that this device is useful for many applications in a variety of settings.

Adult↗
PubMed1977

Role of feedback in the development and maintenance of complex skill.

Three experiments examined the role of various sources of feedback in the development and maintenance of a complex ballistic skill, dart throwing, using extended practice. Even a brief delay of visual feedback initially affected accuracy and consistency adversely, though with practice performance gradually recovered. A total absence of visual feedback impelled subjects to use subtle cues such as crude auditory localization. When these cues were available, accuracy suffered to the same extent as with delayed visual feedback, but consistency in this case was unaffected. When all external feedback was removed, with subjects throwing in the dark at a luminous dot without hearing the dart land, consistency remained unimpaired, but accuracy suffered. However, on returning to full visual feedback both accuracy and consistency were found to have improved when compared to a control group. The independence of accuracy and consistency is discussed in terms of fixed and variable parameters of the skill. The effect of delayed visual feedback is attributed to the failure to integrate visual information with the fading proprioceptive trace. Central importance is attached to improvement in compentence when no external feedback is available, and possible underlying mechanisms for this improvement are described.

Auditory Perception↗
PubMed1976

[Quantitative analysis of characteristics of the negative feedback regulation of ACTH secretion under stress (author's transl)].

Quantitative characteristics and a plausible mechanism of rapid rate-sensitive feedback inhibition of the CRF-ACTH-corticoid system were studied using Nembutal-anesthetized rats. The plasma corticosterone levels were varied by continuous infusion of corticosterone through a lateral caudal vein. The response to an intravenous injection of histamine (as a stressor) was distinctly inhibited in two phases of the dynamics of plasma corticosterone; one in its rapidly increasing phase (rapid rate-sensitive feedback inhibition) and the other, two hours or more after a high plasma steroid level has been attained (late level-sensitive feedback inhibition). On the other hand, there was no such inhibition between these two phases. A quantitative approach made by repeated blood sampling from single rats revealed that the critical rate of elevation of plasma corticosterone at which the rate-sensitive feedback inhibition). On the other hand, there was no such inhibition between these two phases. A quantitative approach made by repeated blood sampling from single rats revealed that the critical rate of elevation of plasma corticosterone at which the rate-sensitive inhibition begins to obviously occur was 4-6 mug%/min. Even with increasing strength of stress, the absolute size of inhibition at a fixed rate of elevation in plasma corticosterone remained almost the same. The increase in the median eminence-CRF activity, known to occur after stress, was effectively suppressed during the operation of rapid feedback inhibition. In addition, in brain noradrenaline-depleted rats, the rapid component in the feedback inhibition was thoroughly abolished, leaving the late component intact, while the opposite way in sorotonin-reduced rats. This finding suggests an involvement of brain biogenic amines in the negative feedback regulation of ACTH secretion in a rather specific way. Finally, on the basis of these results, a plausible model for the rapid rate-sensitive feedback regulation of ACTH secretion under stress was considered.

Adrenocorticotropic Hormone↗
PubMed1979

Reducing auditory feedback and the acquisition of motor response timing.

Three groups of subjects (n=10) attempted to move a lever 50 cm along a track in 1.50 sec under one of three auditory feedback conditions: Fully augmented increasing auditory feedback (FAF) in which a constant level of velocity-related auditory feedback was provided for all 25 learning trials, reducing auditory feedback (FAF) in which the level of feedback was progressively reduced over the learning trials, and no auditory feedback (NAF). All subjects performed 10 trials with no auditory feedback after a 10-min rest interval. The hypothesis that acquisition of the criterion task would be facilitated under RAF compared to FAF derived partial support. It was concluded that there is sufficient evidence to justify further investigation of reducing auditory feedback as a technique of motor skill acquisition.

Auditory Perception↗