Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “FEEDBACK”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40Linked to original sources
PubMed1999

Influence of visual feedback on successive control mechanisms in upright quiet stance in humans assessed by fractional Brownian motion modelling.

An up-to-date way to model the centre of pressure (CP) trajectories may consist in using fractional Brownian motion (fBm). By doing so, one may note that standing still is in fact controlled by two separate and successive mechanisms. The point raised in this study concerns the nature of these control mechanisms and their level of interaction. Following this idea, visual feedback (VFB), which is known to affect postural control by significantly decreasing sway magnitudes, was used. Twelve healthy adults, instructed to stand as still as possible, were tested under this VFB protocol (via a PC screen). In order to model the CP trajectories as fBm, variograms (mean square distances, MSD, expressed as a function of increasing time intervals deltat) were bi-logarithmically plotted. The main visual effect of VFB on these variograms concerns longest latency scaling regimes which reveal less stochastic and consequently more accurate control (P < 0.05 and P < 0.01 for X and Y components, respectively). An increase in the MSD of the transition point, which corresponds to the switch between the two control mechanisms, is also noted (P < 0.05). Overall, evidence is provided from this data that long latency scaling regimes do operate through a feedback process. Interestingly, this improved determinism in feedback control in turn induces a similar effect on the control operating over the shortest deltat. Thus, by privileging a control strategy based on feedback mechanisms, VFB in turn would make the subjects quicker in their initial displacement in order to reach a position capable of initiating a feedback mechanism.

Adult↗
PubMed1999

Externally guided control of static grip forces by visual feedback-age and task effects in 3-6-year old children and in adults.

This study has been devised to examine the visual feedback control of static grip force levels by pinch and by hand grip during pre-school age and in adults. 69 3-6-year old children and 17 adults were asked to establish and hold grip force levels defined by a visual target and feedback on the dominant and non-dominant hand by hand grip and by pinch grip. From 3 to 6 years of age, the time needed to establish requested grip force levels decreased by a third and the precision increased two-fold for hand grip but four-fold for pinch grip; in contrast to younger children, 5-6-year olds showed a marked superiority of 60% for the pinch grip compared to hand grip, decreasing to about 40% in adults. In the case of pinch grip, all individuals had worse results on higher force levels (children: 50%, adults: 32%). The young children generally tended to use too much force. Older children and adults were better by 75% under the condition of visual feedback vs. internal proprioceptive control (after withdrawing visual feedback). In contrast to previous findings in anticipatory grip force regulation, externally guided force regulation begins to develop during late nursery age. Specific developmental effects were found for grip style and for the ability to use visual feedback and to change from external to internal (proprioceptive) control, and to a lesser extent for force magnitude but not for hand laterality and gender. The findings are interpreted by different developmental velocities of motor areas which are responsible for force regulation mechanisms and for grip style.

Adult↗
PubMed1997

Voice F0 responses to pitch-shifted auditory feedback: a preliminary study.

Auditory feedback has been suggested to be important for voice fundamental frequency (F0) control. The present study featured a new technique for testing this hypothesis by which the pitch of a subject's voice was modulated, fed back over earphones, and the resultant change in the emitted voice F0 was measured. The responses of 67 normal, healthy young adults were recorded as they attempted to ignore intermittent upward or downward shifts in pitch feedback while they sustained steady vowel sounds (/a/) or sang musical scales. Ninety-six percent of subjects increased their F0 when the feedback pitch was decreased, and 78% of subjects decreased their F0 when the pitch feedback was increased. Latencies of responses ranged from 104 to 223 ms. Results indicate people normally rely on pitch feedback to control voice F0.

Feedback↗
PubMed2002

Attributes of clinical recommendations that influence change in practice following audit and feedback.

The object of this study was to determine which attributes of clinical practice recommendations influence changes in clinical practice following audit and feedback. This was an observational study using multilevel modeling to examine the relationship between attributes of clinical practice recommendations and compliance with the recommendations before and after audit and feedback. Sixteen hospital gynecology units in Scotland participated in a national audit project. Clinical practice recommendations covering selected gynecological topics were developed and data collected to assess baseline (preintervention) compliance. Summaries of performance were fed back to consultant gynecologists in each hospital and follow-up (postintervention) data were collected. Trained audit assistants used standardized forms to abstract data from case notes. Compliance data were available at baseline and follow-up for a total of 42 clinical practice recommendations. Altogether, 4,664 case notes contributed to baseline data and 4,382 to follow-up data. Thirteen attributes describing clinical practice recommendations were developed, based upon previous work, and pretested. A panel of seven consultant gynecologists rated the extent to which each of the 42 recommendations possessed each of the 13 attributes. The main outcome measures were the association of each attribute with compliance and with changes in clinical practice. Recommendations compatible with clinician values and not requiring changes to fixed routines were independently associated with greater compliance at baseline and follow-up. However, recommendations incompatible with clinician values were independently associated with greater change in practice following audit and feedback. Attributes of recommendations may influence the effectiveness of audit and feedback in secondary care. Recommendations seen as incompatible with clinician values are associated with lower compliance but greater behavioral change following audit and feedback.

Attitude of Health Personnel↗
PubMedDate not supplied

Prenatal melatonin exposure influences the maturation of gonadotropin and prolactin estradiol-benzoate feedback system.

Gonadotropin and prolactin response to estrogen feedback in female rat offspring of control and melatonin treated (150 microg/100 g BW) mother rats during pregnancy (MEL-offspring) were studied at these periods: infantile, prepubertal and pubertal. In controls negative or absent LH feedback developed after estradiol benzoate (EB) injection up to 30 days of age indicating that the onset of puberty had not occurred. The positive feedback was established from day 33 on. However, in MEL-offspring the first activation of gonadotropin secretion during afternoon, 31 h after EB, was observed at 25 days of age, representing the first neuroendocrine sign of the onset of puberty. This positive response disappeared on day 30 in MEL-offspring. At 33 days of age, the LH positive response to EB was found in both groups, indicating a more advanced sexual development. In controls, this response increased at 35 days of age while in MEL-offspring it was highly depressed. FSH secretion in response to EB showed a negative feedback effect from infantile to the end of prepubertal period in both groups. The positive feedback was observed earlier in MEL-offspring (at 33 days of age) than in controls (at 35 days of age), but at this age it was absent in MEL-offspring. A positive prolactin response to EB at all ages in controls was observed. The typical pulsatility with higher values in the afternoon appeared by the first time at 30 days of age. However, in MEL-offspring no pulsatile response was observed throughout any age. These data suggest that prenatal melatonin administration altered gonadotropin and prolactin response to EB inducing precocious sensitivity during prepubertal period but depressed response during the pubertal period.

Animals↗
PubMed2006

The role of performance feedback in the self-assessment of competence: a research study with nursing clinicians.

Performance feedback has the potential to contribute to a nurse's self-awareness and, in turn, their ability to self-assess their level of competence. Because a declaration of self-assessment of competence is a current requirement for continuing nursing registration within South Australia, Queensland and Tasmania, the search to identify sources and processes that may assist nurses to self-assess their performance is potentially of benefit to the profession. This paper is based on one aspect of a PhD study exploring the utility of performance feedback primarily from a nursing clinicians' perspective. Focus group interviews were conducted with hospital-based nursing clinicians and the data were analysed using a process of thematic analysis. Findings highlighted that nursing clinicians frequently engaged in a process of performance self-monitoring that was a balance between feeling competent and feeling uncertain in relation to their own level of clinical competence. On a daily basis, nursing clinicians held an assumption of competence to practise that was based on their ability to act in a situation, receiving positive feedback from others and in the absence of evidence to the contrary. At times feelings of doubt or uncertainty intervened especially in situations that were unfamiliar or challenging or when receiving feedback from others that questioned their own perceptions of competence. The findings of the study provide support for the types of self-monitoring processes that serve to enhance both the relevance of feedback for nurses and the quality of evaluative data regarding ongoing competence.

Australia↗
PubMed2004

Using statewide audit and feedback to improve hospital care in West Virginia.

BACKGROUND: Audit and feedback systems have significantly improved medical care in numerous settings, and they appear to work by stimulating competition rather than through command and control. METHODS: The West Virginia Medical Institute (WVMI), a Medicare-designated Quality Improvement Organization (QIO), periodically collected quality information on five common conditions (acute myocardial infarction [AMI], heart failure, pneumonia, stroke, and atrial fibrillation) that cause hospitalization in Medicare beneficiaries. All 44 acute care hospitals in West Virginia were offered written and orally presented reports of quality performance from 1998 through 2001. RESULTS: All indicators appeared to improve statewide. Several--for example, aspirin at discharge for AMI patients and pneumococcal vaccine for pneumonia patients--improved by more than 10 absolute percentage points. Fourteen of 15 quality indicators showed significant improvement (p < .05, paired t-test) in all hospitals between the before- and after-feedback periods. Seven of 13 indicators assessed during the entire study in the largest hospitals showed no significant trends in quality before feedback but significant increases (p < .05, chi-square for trend) in the after-feedback period. DISCUSSION: The quality indicator changes reported can represent important health gains for West Virginia Medicare beneficiaries. Most of the improvement did not occur until after hospitals received feedback.

Feedback↗
PubMed1998

Abnormal neural response to feedback on planning and guessing tasks in patients with unipolar depression.

BACKGROUND: It has been suggested that patients with unipolar depression show abnormal responses to negative feedback in the performance of cognitive tasks. Positron emission tomography (PET) has previously identified blood flow abnormalities in depressed patients during cognitive performance. We have also used PET to identify regions where there is differential neural response to performance feedback in normal volunteers. In this study we aimed to test the hypothesis that blood flow in these regions, the medial caudate and ventromedial prefrontal cortex, would be abnormal in depressed patients. METHODS: Six patients with unipolar depression and six matched controls were scanned using PET while performing cognitive tasks in the presence and absence of feedback. RESULTS: Compared with controls, depressed patients failed to show significant activation in the medial caudate and ventromedial orbitofrontal cortex. Blood flow was lower and a differential response, observed in normals, under different task and feedback conditions was not seen in the patients. DISCUSSION: The findings suggest that the behavioural response to feedback in depressed patients is associated with an abnormal neural response within the medial caudate and ventromedial orbitofrontal cortex, regions implicated in reward mechanisms. We argue that the observed abnormalities may depend on a combination of psychological factors, with both cognitive and emotive components.

Adult↗
PubMedDate not supplied

Brightness perception, illusory contours, and corticogeniculate feedback.

A neural network model is developed to explain how visual thalamocortical interactions give rise to boundary percepts such as illusory contours and surface percepts such as filled-in brightnesses. Top-down feedback interactions are needed in addition to bottom-up feed-forward interactions to simulate these data. One feedback loop is modeled between lateral geniculate nucleus (LGN) and cortical area V1, and another within cortical areas V1 and V2. The first feedback loop realizes a matching process which enhances LGN cell activities that are consistent with those of active cortical cells, and suppresses LGN activities that are not. This corticogeniculate feedback, being endstopped and oriented, also enhances LGN ON cell activations at the ends of thin dark lines, thereby leading to enhanced cortical brightness percepts when the lines group into closed illusory contours. The second feedback loop generates boundary representations, including illusory contours, that coherently bind distributed cortical features together. Brightness percepts form within the surface representations through a diffusive filling-in process that is contained by resistive gating signals from the boundary representations. The model is used to simulate illusory contours and surface brightness induced by Ehrenstein disks, Kanizsa squares, Glass patterns, and café wall patterns in single contrast, reverse contrast, and mixed contrast configurations. These examples illustrate how boundary and surface mechanisms can generate percepts that are highly context-sensitive, including how illusory contours can be amodally recognized without being seen, how model simple cells in V1 respond preferentially to luminance discontinuities using inputs from both LGN ON and OFF cells, how model bipole cells in V2 with two colinear receptive fields can help to complete curved illusory contours, how short-range simple cell groupings and long-range bipole cell groupings can sometimes generate different outcomes, and how model double-opponent, filling-in and boundary segmentation mechanisms in V4 interact to generate surface brightness percepts in which filling-in of enhanced brightness and darkness can occur before the net brightness distribution is computed by double-opponent interactions.

Computer Simulation↗
PubMedDate not supplied

The effect of a quality improvement feedback loop on paramedic skills, charting, and behavior.

OBJECTIVE: A mechanism was initiated for conveying quality improvement (QI) results to paramedics as a means of improving chart documentation in difficult-to-correct areas. This study examines the impact of this QI feedback loop on charting, resuscitation rates from cardiac arrest, endotracheal intubation (ETI) success rates, and trauma scene times. DESIGN: Paramedic trip sheets were reviewed before and after the institution of the QI feedback loop in this interrupted time series design. SETTING: The New Castle County, Delaware, Paramedic Program. PARTICIPANTS: All New Castle County paramedics participated in the study. INTERVENTIONS: In January 1990, the medical director began to circulate a QI summary among the paramedics in an effort to improve performance and chart documentation. The summary focused on the management of respiratory distress or arrest, cardiac arrest, and major trauma. The success rate for ETI was compared with the rate of field resuscitation from cardiac arrest, the percentage of unjustified prolonged trauma scene times (longer than 10 minutes), and the percent compliance with minimum endotracheal intubation documentation (ETID) requirements from a six-month period before institution of the QI feedback mechanism with data obtained from a six-month period after the program had been operational for one year. RESULTS: Comparing results from before with after the initiation of the QI program, the ETI success rate was 273 of 295 (92.5%) before and 300 of 340 (88.2%) after (chi 2 = 3.04, p < .1, ns); field resuscitations totaled 26 of 187 (13.9%) before and 44 of 237 (18.6) after (chi 2 = 1.40, p < .25, ns); ETID rate was 249 of 295 (84.4%) before and 336 of 340 (98.8%) after (chi 2 = 44.24, p < .001), and unjustified prolonged trauma scene times were 69 of 278 (24.8%) before and seven of 501 (1.4%) after (chi 2 = 320.5, p < .001). CONCLUSION: The use of QI feedback had little effect on psychomotor skills as the ETI success rate or resuscitation rate, but had a dramatic effect on chart documentation, as evidenced by ETID rate, and behavior, as evidenced by the reduction in prolonged trauma scene times. The use of QI feedback is recommended as a means of correcting charting deficiencies or modifying behavior.

Clinical Competence↗
PubMed1999

Regulation of phenylalanine biosynthesis. Studies on the mechanism of phenylalanine binding and feedback inhibition in the Escherichia coli P-protein.

Isothermal titration calorimetry (ITC) and site-directed mutagenesis were used to study the interaction of Phe with (a) the Escherichia coli P-protein, a bifunctional chorismate mutase/prephenate dehydratase that is feedback inhibited by Phe, (b) PDT32, a 32 kDa P-protein fragment (residues 101-386) containing the prephenate dehydratase and regulatory domains, and (c) R12, a C-terminal 12 kDa P-protein fragment (residues 286-386) containing the regulatory domain. DeltaH(total) values for PDT32, which included the heats of Phe binding, conformational change, and dimerization, established that in developing a mechanism for end product feedback inhibition, the P-protein has evolved a ligand recognition domain that exhibits Phe-binding enthalpies comparable to those reported for other full-fledged amino acid receptor proteins. Sequence alignments of R12 with other Phe-binding enzymes identified two highly conserved regions, GALV (residues 309-312) and ESRP (residues 329-332). Site-directed mutagenesis and ITC established that changes in the GALV and ESRP regions affected Phe binding and feedback inhibition to different extents. Mutagenesis further showed that C374 was essential for feedback inhibition, but not for Phe binding, while W338 was involved in Phe binding, but not in the Phe-induced conformational change required for feedback inhibition.

Bacterial Proteins↗
PubMedDate not supplied

A computational study of feedback effects on signal dynamics in a mitogen-activated protein kinase (MAPK) pathway model.

Exploiting signaling pathways for the purpose of controlling cell function entails identifying and manipulating the information content of intracellular signals. As in the case of the ubiquitously expressed, eukaryotic mitogen-activated protein kinase (MAPK) signaling pathway, this information content partly resides in the signals' dynamical properties. Here, we utilize a mathematical model to examine mechanisms that govern MAPK pathway dynamics, particularly the role of putative negative feedback mechanisms in generating complete signal adaptation, a term referring to the reset of a signal to prestimulation levels. In addition to yielding adaptation of its direct target, feedback mechanisms implemented in our model also indirectly assist in the adaptation of signaling components downstream of the target under certain conditions. In fact, model predictions identify conditions yielding ultra-desensitization of signals in which complete adaptation of target and downstream signals culminates even while stimulus recognition (i.e., receptor-ligand binding) continues to increase. Moreover, the rate at which signal decays can follow first-order kinetics with respect to signal intensity, so that signal adaptation is achieved in the same amount of time regardless of signal intensity or ligand dose. All of these features are consistent with experimental findings recently obtained for the Chinese hamster ovary (CHO) cell lines (Asthagiri et al., J. Biol. Chem. 1999, 274, 27119-27127). Our model further predicts that although downstream effects are independent of whether an enzyme or adaptor protein is targeted by negative feedback, adaptor-targeted feedback can "back-propagate" effects upstream of the target, specifically resulting in increased steady-state upstream signal. Consequently, where these upstream components serve as nodes within a signaling network, feedback can transfer signaling through these nodes into alternate pathways, thereby promoting the sort of signaling cross-talk that is becoming more widely appreciated.

Animals↗
PubMed2004

Cyclic exchanges and level of coupling between environmental media: intermedia feedback in multimedia fate models.

The importance of cyclic transport of chemicals between media in the environment can be expressed in terms of the Feedback correction factor--a multiplier that accounts for the fraction of an emission that returns to the medium of release after transfer to other media. This factor is calculated analytically by explicitly solving the appropriate system of mass balance equations or using matrix techniques. It generalizes the concept of stickiness, the ratio between the net and the overall deposition rate constants, to multipathway feedback, while providing a clearer view of the level of coupling between media and analyzing the importance of coupling. This paper first shows the usefulness of the total removal rate coefficient in each media (sum of degradation rate and all intermedia transfer rates) as a baseline to determine the chemical mass in different media, the characteristic travel distance and to understand the cyclic behavior, rather than starting from the degradation lifetimes or the overall persistence in the environment. Starting from this baseline, the importance of feedback is limited for most organic chemicals. The predicted media concentrations are influenced by less than 10% due to the cyclic nature of the intermedia transport for more than 90% of the 317 tested chemicals in a 4-compartment, steady-state, closed-system multimedia model. The Feedback correction factor is always less than a factor of 5 with the greatest values when transfer fractions are important in both directions for adjacent media. This corresponds to a restricted range in the K(AW) and K(OA) space with long chemical lifetimes in both adjacent media. This analysis of the importance of the Feedback correction factor, in conjunction with resultant criteria for when cyclic exchanges between media are likely to be significant, facilitates a more transparent understanding of how substance masses are distributed in the modeled system. It is one of the important criteria to determine to what extent media can be independently modeled.

Air↗
PubMed2006

Contrast enhancement by feedback fields in magnetic resonance imaging.

A conceptually new approach giving rise to contrast enhancement by feedback fields in magnetic resonance imaging is proposed, and the detailed mechanism is described. Nonlinear spin dynamics under the feedback fields of the distant dipolar field and/or radiation damping are examined and shown to amplify contrast due to small variations in spin density and precession frequency. Feedback-based contrast enhancement depends on the instability of the initial magnetization configuration and is propagated by positive feedback, as shown through numerical simulations and experimental results on simple phantom samples. On the basis of a theoretical understanding of contrast enhancement, insight into pulse sequence design and optimal contrast attainable under the individual and joint feedback fields is provided.

Contrast Media↗
PubMed2004

Self-perceived competence as a mediator between maternal feedback and depressive symptoms in adolescents.

Self-report, other-report, clinical interview, and behavioral observations of evaluative maternal feedback (e.g., positive feedback, criticism), adolescent depressive symptoms, and self-perceived competence were obtained from 72 adolescents and their mothers. Most path analyses supported the hypothesis that adolescent self-perceived competence completely mediates the relation between negative maternal feedback and adolescent depressive symptoms, even after controlling for prior levels of depression. Consistent with Cole's competency-based model of depression (D. A. Cole, 1990), these results suggest that high levels of negative maternal feedback (coupled with low levels of positive feedback) are associated with adolescent negative self-perceptions, which in turn place adolescents at risk for depressive symptoms.

Adolescent↗
PubMed2004

Lost in thought: cognitive load and the processing of addressees' feedback in verbal communication.

Two experiments tested if cognitive load interferes with perspective-taking in verbal communication even if feedback from the addressee is available. Participants gave instructions on the assembly of a machine model. In Experiment 1, cognitive load was demonstrated to be a function of the complexity of assembly steps. In Experiment 2, position of feedback (during simple vs. during complex steps) and type of feedback (question vs. ambiguous interjection) were manipulated. With simple steps, speakers' responses were a function of feedback type. Speakers responded differently to questions than to interjections. With complex steps, however, responses were a function of cognitive load. Regardless of the type of feedback, most speakers simply repeated their previous utterances.

Cognition↗
PubMed1980

Nonverbal behavior and the theory of emotion: the facial feedback hypothesis.

The facial feedback hypothesis, that skeletal muscle feedback from facial expressions plays a causal role in regulating emotional experience and behavior, is an important part of several contemporary theories of emotion. A review of relevant research indicates that studies reporting support for this hypothesis have, without exception, used within-subjects designs and that therefore only a restricted version of the hypothesis has been tested. Also, the results of some of these studies must be questioned due to demand characteristics and other problems. It is suggested that visceral feedback may make a more direct contribution to emotional processes than facial feedback does and that the "readout" functions of facial expressions are more important than any feedback functions.

Emotions↗
PubMed1990

The fleeting gleam of praise: cognitive processes underlying behavioral reactions to self-relevant feedback.

We propose that a preference for favorable social feedback (i.e., self-enhancement) requires only that feedback be characterized as favorable or unfavorable but that a preference for self-confirming feedback (i.e., self-verification) is based on a more elaborate set of cognitive operations that requires both the characterization of feedback and a subsequent comparison of that feedback to a representation of self stored in memory. Study 1 set the stage for testing this hypothesis by showing that depriving people of processing resources interfered with their tendency to access their self-conceptions. In Studies 2 and 3, participants who were deprived of resources preferred the favorable, self-enhancing evaluator, whereas control participants displayed a preference for the self-verifying evaluator, even if that evaluator was relatively unfavorable.

Adult↗