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PubMed1990

Facial and verbal congruency: effects on perceived verbal and emotional coaching feedback.

The present study investigated the effects of facial-verbal expression congruencies on the perception of a coach's verbal and emotional feedback. The design was a two (facial congruency) by two (verbal feedback) completely randomized factorial. The facial expression was either congruent or incongruent with verbal feedback. Seventy-one university students (39 males, 32 females) were randomly assigned to one of the four experimental conditions. Each student watched a videotape of facial-verbal pairings and evaluated (a) the percentage of positive and negative statements, (b) the emotions expressed by the coach. The analysis indicated that incongruent facial expressions distorted, in a negative direction, the expected frequency of positive feedback. The emotional state findings illustrated that the presence of any negative stimuli (face or verbal) produced the perception of negative affect. The findings provided converging evidence that inconsistencies in facial-verbal expression have a powerful effect on the perception of verbal feedback and emotional state.

Adolescent↗
PubMedDate not supplied

PAF/cytokine auto-generated feedback networks in microvascular immune injury: consequences in shock, ischemia and graft rejection.

The catastrophe theory evolved by Thom and Zeeman proposes a mathematical definition for the abrupt or 'catastrophic' changes that can suddenly occur in normally well-ordered and smooth-running systems. We have integrated this theory with our own PAF/cytokine feedback network hypothesis to explain the control and dysfunction of the inflammatory response. This process involves the activation of cells and factors such as proteases, and is coordinated by mediators such as PAF, cytokines and growth factors, minute amounts of which can prime cells to respond in an enhanced manner to subsequent agonistic stimuli. PAF and certain cytokines also possess the unique property of being able to induce the release of each other and their own generation in vivo. This 'singularity' may enable a self-generating feedback network to become established. The priming ability of these mediators indicates the extreme sensitivity of the inflammatory process and importance of a homeostatic equilibrium between the vectors involved in the priming and feedback processes and internal suppressive mechanisms. In pathological conditions, one can consider the phenomenon of PAF and cytokine autogeneration as a 'fold' in the feedback network and an expression of the singularity characteristic of the catastrophe hypothesis. This may lead to systemic toxicity and microcirculatory collapse, a characteristic feature of shock, sepsis, asthma, ischemia and graft rejection. A combination of drugs antagonizing the various feedback components may inhibit this catastrophic process and thus provide more successful therapy of these conditions.

Animals↗
PubMed1989

Assigned and participative production standards and feedback affecting worker productivity in a repetitive production task.

The main objective of this research was to determine the effects of assigned and participative standards in conjunction with feedback on worker productivity in a repetitive production task. An assigned hard standard and feedback was significantly better than a participative standard and feedback in terms of quality output but no significant difference in quantity output was found between them. Thus from the overall worker productivity viewpoint, the former condition was superior to the latter condition. Both conditions provided a significant improvement in worker productivity. The percentage increases in quantity and quality output for the assigned hard standard and feedback condition were 12% and 7%, respectively, compared to the control group. The assigned normal standard and feedback had a significant positive impact on quantity output but no significant effect was found in terms of quality output.

Efficiency↗
PubMed1988

Ratings of clinical clerkship feedback by allied health faculty and students.

The purpose of this survey study was to investigate allied health faculty members' and students' ratings of the clinical educational feedback process. Faculty members and students from seven allied health programs at the University of Nebraska Medical Center, who were currently involved with clinical education, were asked to indicate their feelings on a seven-point scale for each of 22 feedback characteristics. An ANOVA and a Scheffe's test for post hoc analysis were used for data analyses. The results indicated that while both faculty members and students perceived eight feedback characteristics as equally important, they differed significantly (p less than .01) in their ratings of actual feedback provided in the characteristics of specific, timely, encouraging, and recommending improvement. Other significant faculty/student discrepancies were found in the area of student reception of feedback provided. The results are useful to guide and direct improvements in the clinical education of allied health students.

Allied Health Personnel↗
PubMed1977

Significance of different feedbacks for the transient processes of the discharges of single motor units during step-like voluntary movements.

Studies are made of the transient processes of the discharges of single tonic low-threshold and phasic high-threshold motor units (MUs) during step-like voluntary movements performed in case of visual feedback by the result of the movement and in case of artificial auditory feedback by the sound of the MU impulses, as well as in cases of absence of exteroceptive feedback. The studies comprise isometric and isotonic flexion and extension in the elbow joint, the MUs studied being from m. biceps brachii. The previously observed differences of the transient processes in tonic and phasic MUs are found to exist not only during movements taking place under visual control but also under other conditions studied. Under conditions of articicial auditory feedback the subjects may or may not use this feedback for control of the motor response.

Adult↗
PubMed1982

Renin-angiotensin influences on tubuloglomerular feedback activity in the rat.

We have reviewed the development of Thurau's hypothesis that angiotensin mediates the effector responses of distal tubuloglomerular feedback-induced changes of nephron function. Several studies attempting to correlate responsiveness of the tubuloglomerular feedback system with intrarenal renin or juxtaglomerular renin contents have not delineated angiotensin's role in the feedback control system. Others and our own recent studies that have assessed the effects of acute blockade of the renin-angiotensin system on the responsiveness of tubuloglomerular feedback activity suggest that the effects of angiotensin are most likely a modulating influence on the activity of the system rather than the mediator of feedback-induced changes in glomerular function.

Angiotensins↗
PubMed1984

The role of feedback from the vocal organ. I. Maintenance of stereotypical vocalizations by adult zebra finches.

The stereotypical vocal patterns of adult male zebra finches (Poephila guttata) were examined before and after elimination of auditory feedback and/or feedback from the vocal organ (the syrinx). Elimination of auditory feedback was accomplished via bilateral removal of the cochleae, whereas feedback from the syrinx was eliminated by cutting hypoglossal afferent fibers while leaving hypoglossal efferents intact. Very little or no disruption of song was observed in birds which underwent deafening as well as unilateral deafferentation of the syrinx. Control experiments showed that the minor deficits observed were not attributable to lesion of pulmonary fibers in the descending branch of the vagus. There was also little deficit in song behavior of birds that were deafened and subjected to bilateral deafferentation of the syrinx. These results are consistent with the hypothesis that stable song patterns in adult passerine birds are not dependent on peripheral sources of feedback, but may be governed by a learned central control program.

Afferent Pathways↗
PubMed1982

Interrelationship between proximal tubular hydrodynamics and tubuloglomerular feedback in the rat kidney.

We have investigated the extent of interaction between the tubuloglomerular feedback mechanism (TGF) and the proximal tubular pressure-mediated changes in glomerular filtration rate (GFR) in hydropenic Wistar rats without interfering with the feedback loop. Infusing or withdrawing tubular fluid at rates up to 5 nl/min from a late proximal site in a free-flowing nephron caused little change in late proximal tubular pressure, implying that GFR varied inversely and proportionately to maintain a constant late proximal flow. By blocking the same tubule and measuring early proximal flow rate during perfusion together with late proximal tubular pressure, we were able to deduce both the feedback curve in the "open-loop" mode and the pressure-flow relationship for the loop of Henle. From these relationships and the free-flow pressure curve, we constructed the feedback curve for the "closed-loop" mode to get the pressure-constant phase. The steady-state operating points lay close to the steepest part of the open-loop curve, suggesting that the feedback normally operates in its most sensitive range. Fluid infusion or withdrawal at rates in excess of 5 nl/min led to nonlinear increases or decreases in intratubular pressure, respectively. It is concluded that for small changes in the loop of Henle inflow around the normal value, TGF operates alone and compensates remarkably accurately. For changes outside this range, concomitant changes in proximal intratubular pressure may reinforce the action of the TGF.

Animals↗
PubMed1995

Providing feedback.

Although the importance of providing feedback to our fellows, residents, and colleagues is acknowledged, this key step in the acquisition of clinical skills is often omitted from training programs. When effective feedback is provided and focuses on directly observable skills and behaviors, important personal and educational progress can occur. This article presents the key components of formative feedback as distinct from performance evaluation; discusses the barriers to providing effective feedback; and makes specific suggestions for beginning the process of giving useful feedback to trainees.

Clinical Competence↗
PubMed1995

Negative feedback regulation of the secretion and actions of GnRH in male ruminants.

The roles of testicular hormones in the negative feedback regulation of the secretion and actions of GnRH in male domestic ruminants are reviewed, concentrating mainly on research conducted with rams. Testicular steroids have major feedback actions directly at the hypothalamus to inhibit the secretion of GnRH, although it is apparent that, under certain circumstances, the steroids also have actions directly at the pituitary gland. Further research is necessary to delineate these actions and to determine the contribution of testosterone and its primary metabolites, dihydrotestosterone and oestradiol, to negative feedback on the hypothalamo-pituitary unit. Since GnRH neurones do not possess receptors for steroids, testicular steroids must evoke other neuronal pathways to influence GnRH producing neurones. While the opioids may be important in this regard, it is necessary to determine which other neuronal pathways may also be involved to understand fully the mechanism of action of testicular steroids. It appears that the feedback regulation of the secretion of LH can be accounted for by testicular steroids, whereas the secretion of FSH is influenced by inhibin and steroids, and possibly the recently isolated proteins follistatin and activin. The actions of inhibin to suppress the secretion of FSH occur at the pituitary gland and not on the synthesis or secretion of GnRH. There is a complex interaction between testosterone and inhibin in the control of FSH secretion that results in synergistic effects during the non-breeding season but not during the breeding season. Activin has been shown to have FSH-stimulating properties and follistatin has been shown to have FSH-inhibiting properties, but it is unknown if these proteins play a physiological role in the feedback regulation of FSH in male domestic ruminants.

Androgens↗
PubMedDate not supplied

Evaluation of the tubuloglomerular feedback system in human subjects.

It has been shown in animals that GFR decreases after administration of a carbonic anhydrase inhibitor (CAI) because of activation of the tubuloglomerular feedback. However, the magnitude of this response has never been studied in healthy subjects, nor has the possibility of inhibiting tubuloglomerular feedback with frusemide (FRU). Changes in CCr, V, CNa, CCl, CH2O, CLi were studied before and after acute administration of acetazolamide (ACZ) to 11 normal subjects or FRU to 9 normal subjects. Both ACZ and FRU increased V, CNa, CCl and CLi. Only FRU decreased CH2O. ACZ but not FRU decreased CCr, despite lesser increases of V, CLi and CH2O+CCl (rough indexes of distal delivery). The magnitude of the GFR decrease after comparable increases in distal delivery varied greatly between subjects. There was a tendency for the subjects with lower basal GFRs to show tubuloglomerular feedback responses of lesser magnitude than those with higher GFRs. These results show that it is possible to study tubuloglomerular feedback and its sensitivity in humans using CAIs. FRU blocks the tubuloglomerular feedback response. Its sensitivity appears to vary widely in normal subjects.

Acetazolamide↗
PubMed1995

Negative feedback neuroendocrine control of the inflammatory response in rats.

We describe that an ongoing inflammatory response at one site (produced by complete Freund's adjuvant injection in the hindpaw) produces a negative feedback inhibition on plasma extravasation, produced by perfusion of the inflammatory mediator, bradykinin (160 nM), at a second site (the knee joint). This negative feedback process is abolished in rats that have been neonatally treated with capsaicin to deplete most of their unmyelinated primary afferent fibers, which suggests that this negative feedback process is mediated by activation of primary afferent fibers. Electrical stimulation of the hindpaw at intensities that excite C-fibers also inhibited bradykinin-induced plasma extravasation. Stimulation at intensities that only excite A-fibers had no effect on bradykinin-induced plasma extravasation. Platelet activating factor-induced plasma extravasation, which is not dependent on the innervation of the joint, was not inhibited by stimulation of C-fibers from the hindpaw. Acute surgical interruption of the lumbar sympathetic outflow to the hind limb (the paravertebral ganglia between L2 and L4) did not attenuate the depression of bradykinin-induced plasma extravasation produced by C-fiber stimulation. This indicates that the depression is not mediated by activity in the sympathetic outflow. Transection of the spinal cord, hypophysectomy, inhibition of corticosterone synthesis, and adrenalectomy (but not adrenal medullectomy) all prevented the inhibition of BK-induced plasma extravasation by electrical simulation, indicating that the negative feedback inhibition on plasma extravasation is dependent on an intact neuraxis and an intact hypothalamic-pituitary-adrenocortical axis. In summary, our data demonstrate a negative feedback inhibition of an inflammatory process, which is elicited by stimulation of C-fiber afferents.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1993

Comparing different types of performance feedback and computer-based instruction in teaching medical students how to diagnose acute abdominal pain.

PURPOSE: To examine the relative efficacies of three types of performance feedback used with computer-based instruction (CBI) in making diagnoses. METHOD: In 1990, 75 final-year medical students at The University of Queensland were pretested for domain knowledge and diagnostic skill in the area of acute abdominal pain. The students were also asked to indicate their confidence in each of their diagnoses. Following these pretests, the students were randomly divided into five groups of 15 students each. One group received traditional CBI, using a "question-and-explanation" format, to learn domain knowledge. The other four groups received one of two types of CBI to learn diagnostic accuracy, and these four groups received one of three types of performance feedback (which differed considerably in the amounts of information imparted). Then the students took posttests. One-way analysis of variance, Student's t-test, and the Tukey test were used to compare the performances of the different groups of students. RESULTS: Although the students in the traditional CBI group significantly improved their performance on multiple-choice questions (by 58%) compared with the other groups of students (6-10% improvement), these students did not improve their diagnostic performance. In contrast, the CBI groups that used simulated-patient cases and structured-performance feedback did improve their diagnostic accuracy (by as much as 16%, compared with a 1% decline for the traditional CBI group). Contrary to expectation, the different types of feedback were equally effective. Except for the students in the traditional CBI group, the students' confidence increased from pretest to posttest regardless of their performances. CONCLUSION: CBI that uses simulated-patient cases and structured-performance feedback seems to be efficient and effective compared with traditional CBI methods. However, care should be taken to ensure that students do not become overconfident of their abilities.

Abdominal Pain↗
PubMed1997

Positive feedback modulation of acetylcholine release from isolated rat superior cervical ganglion.

The effects of selective nicotinic acetylcholine (ACh) receptor (nAChR) agonists and antagonists on the stimulation-evoked release of [3H]ACh were studied in rat isolated superior cervical ganglion loaded with [3H]choline and superfused in a 2-ml chamber. Nicotine and 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP), but not cytisine, increased the stimulation (2 Hz)-evoked release of [3H]ACh in a concentration-dependent manner. The rank order of potency to increase stimulation-evoked release for the nAChR agonists (nicotine > DMPP >> cytisine) suggests that the beta4 subunit of nAChRs is not involved in the release. The finding that alpha-bungarotoxin was effective in preventing the effect of DMPP and itself significantly reduced the release indicates that the alpha7 subunit is located presynaptically and may be involved in the positive feedback modulation. Hexamethonium inhibited the effect of DMPP with an apparent dissociation constant (Kd) of 11.5 +/- 1.5 microM. Hexamethonium and other nAChR antagonists, i.e., (+)-tubocurarine (100 microM), mecamylamine (3 microM), dihydro-beta-erythroidine (3 microM), pancuronium (10 microM) and alpha-bungarotoxin (2 microM), also decreased the stimulation-evoked release of [3H]ACh. The effect of hexamethonium was independent of stimulation frequency (2, 10 and 30 Hz) applied. Atropine enhanced the stimulation-evoked release of ACh, indicating that there is negative feedback modulation of ACh release associated with neuronal activity. In contrast, when the nicotinic positive feedback was prevented by hexamethonium, atropine failed to enhance the release. These findings indicate that muscarinic receptor-mediated inhibition of ACh release functions in cases in which the release is enhanced by ACh via stimulation of presynaptic nAChRs. A similar interaction was found between A1 receptor-mediated reduction and nAChR-mediated positive feedback modulation of [3H]ACh release. The results suggest the presence of positive feedback modulation of ACh release via presynaptic nAChRs in rat superior cervical ganglion.

Acetylcholine↗
PubMed2004

Thermal therapy of canine cerebral tumors using a 980 nm diode laser with MR temperature-sensitive imaging feedback.

BACKGROUND AND PURPOSE: The laser-induced thermal therapy (LITT) of cerebral tumors has conventionally been performed using Nd:YAG lasers and is associated with a risk of high focal temperatures potentially followed by cavitation that could result in boiling and/or explosive char. We have developed small diffusing laser fiber tips to better distribute the energy deposition and a computer controlled feedback system to monitor therapy and prevent excess temperature buildup. In this study, we evaluated the feasibility of using magnetic resonance temperature imaging (MRTI)-based feedback system for the thermal treatment of experimental intracerebral tumors using 980 nm laser irradiation delivered through these diffusing tips. STUDY DESIGN/MATERIALS AND METHODS: Transmissible venereal tumors (TVTs) were grown via inoculation in the right cerebral hemisphere of seven canines. The laser fiber tips were inserted into a total of 10 independent TVT-suspected regions in the seven animals. Margins for the target area in each animal were prescribed on the basis of pretreatment MR images. MRTI-based feedback software was used to measure and regulate both temperature and the delivered thermal dose to achieve the desired thermal ablation and prevent excess heating. The effects of treatment were verified by results of histologic analyses. RESULTS: Treatments resulted in contiguous areas of thermal necrosis in tumors and adjacent brain margin. The feedback software successfully cut off the laser power once the desired treatment volume was achieved, and prevented focal temperatures from exceeding predefined thresholds. Follow-up MRI studies showed 1.4- to 2.9-fold LITT-induced lesion expansion within 1-6 days after treatment. CONCLUSIONS: Targeted thermal coagulation of small intracerebral tumors is feasible using MRTI-based feedback and diffused 980 nm diode laser light.

Animals↗
PubMed2000

Socio-affective characteristics and properties of extrinsic feedback in physiotherapy.

BACKGROUND AND PURPOSE: The usual approach in physiotherapy is to communicate the desired action by means of some combination of verbal instruction and explanation, visual demonstration and manual assistance. Patients' and physiotherapists' communication and acts express socio-affective elements which influence the atmosphere governing this interaction. The purpose of this study was to investigate the socio-affective characteristics of the verbal, visual and manual feedback given to their patients by physiotherapists in the performance of their duties. METHOD: Data were collected by videotaping patient-physiotherapist interaction. Systematic observation was used to depict physiotherapists' and patients' verbal and physical communications. The observation instrument consisted of the categories of verbal communication, physical activities and the socio-affective features of communication. RESULTS: The physiotherapists used verbal and physical guidance more and visual guidance less. In the main, the properties of the feedback given were motivational and reinforcing. Information feedback appeared very seldom. Verbal cues were mostly short comments. The main significance of manual cueing was in the tactile input that was used in orienting patients to produce the correct movement. The most effective way of helping patients to understand the purpose of the action and the sequential organization of the subroutine of the movement was to give a demonstration containing the relevant visual and verbal cues. CONCLUSIONS: The extensive use of verbal and manual guidance found in this study needs to be thought over carefully, especially as physiotherapists seemed to use these techniques more as routine than as a result of careful consideration. The socio-affective atmosphere seems to influence physiotherapists' ways of giving feedback to their patients. Further research is needed to determine the most effective way of arranging guidance strategies for physiotherapists to produce effective feedback.

Aged↗
PubMed1977

Cephalic vasomotor feedback in the modification of migraine headache.

The effect of cephalic vasomotor response (CVMR) and frontalis electromyographic (EMG) feedback on control of temporal arterial vasoconstriction and frontalis muscle activity in migraine and muscle contraction headache patients was investigated. A single subject multiple baseline design (across subjects and responses) was introduced to evaluate (1) patterning in the two physiological systems and (2) the effects of CVMR and EMG feedback on headache activity. The data indicated that (a) all four patients demonstrated an ability to control CVMR activity during CVMR feedback and EMG during EMG feedback, (b) idiosyncratic patterns of physiological activity emerge during feedback training, and (c) learned control of the pain mechanism for muscle contraction and migraine headaches was related to reduced frequency and duration of these headaches.

Adolescent↗
PubMed1984

The effect of activation versus inhibition of feedback on perceived control of EEG activity.

This study explores a model in which perceived control is affected by multiple sources of feedback at three different stages of the control sequence--person, response, and outcome. Behavior that enhances feedback is termed activation, while behavior that diminishes feedback is termed inhibition. The study tests the hypothesis that activation at any stage of the sequence leads to greater perceived control than inhibition. Eighty subjects increased or decreased their brain-wave activity (EEG) by making a tone go either on or off, using either an active or a passive strategy. Following 10 60-second trials, subjects rated their perception of control over their EEG activity. The hypothesis that making a tone go on (activation of the outcome) leads to a greater perception of control than making the tone go off (inhibition of the outcome) was confirmed only when subjects decreased their EEG activity. Perceived control was not significantly correlated with actual control, supporting the expectation that they are separately mediated. The results did not support the hypothesis that increasing EEG activity or using an activity strategy would lead to a greater perception of control than decreasing EEG or using a passive strategy. These findings are interpreted as evidence that attention to feedback may be necessary for the predicted bias in perceived control to occur, and that activation and inhibition should be operationalized as the absolute presence versus absence of feedback in testing the hypothesis for the first two stages of control.

Adolescent↗