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PubMed1991

Feedback theory and Darwinian evolution.

Feedback loops can have a significant impact on biological systems that are evolving under Darwinian natural selection. Many of the striking and sometimes bizarre patterns that characterize the evolution of such systems have simple, natural explanations that involve the effects of feedback loops. The two fundamental types of feedback loops, positive and negative, have effects that are radically different: negative feedback tends to produce stability and resistance to change; positive feedback produces instability and even catastrophe. Both types of feedback loops are important in biological systems, and both can produce chaos, whose mathematical complexity often produces strange, beautiful and totally unexpected patterns that have only begun to be explored using the computational capabilities of modern electronic computers. An understanding of the patterns that can result from the effects of feedback loops can produce important new insights into the patterns that mark the evolutionary development of biological systems.

Animals↗
PubMed1999

The feedback pathway from horizontal cells to cones. A mini review with a look ahead.

The feedback pathway from HCs to cones forms the basis of the surround responses of the bipolar cells and is essential for the spectral opponency of horizontal cells. The nature of this feedback pathway is an issue of debate. Three hypothesis are presented in literature: (1) a GABAA-ergic feedback pathway; (2) a GABA-independent feedback pathway that modulates the Ca-current in cones; and (3) an electrical feedback pathway. In this review the evidence for the various pathways will be discussed. The conclusion is that the available evidence favors the hypothesis that feedback modulates the Ca-current in the cones in a GABA independent way. An alternative role of GABA in the outer plexiform layer is discussed and finally the functional consequences of the negative feedback pathway from horizontal cells to cones are presented.

Animals↗
PubMed1995

Randomised controlled trial of routine individual feedback to improve rationality and reduce numbers of test requests.

Feedback can be described as a way to provide information on doctors' performance to enable changes in future behaviour. Feedback is used with the aim of changing test-ordering behaviour. It can lead to reductions in test usage and cost savings. It is not sufficiently clear, however, whether feedback leads to more appropriate test use. Since 1985, the Diagnostic Coordinating Center Maastricht has been giving feedback on diagnostic tests as a routine health care activity to all family doctors in its region. Both quantity and quality of requests are discussed. In a randomised, controlled trial over 2.5 years, discussion of tests not included previously was added to the existing routine feedback. One group of family doctors (n = 39) received feedback on test-group A (electrocardiography, endoscopy, cervical smears, and allergy tests), the other (n = 40) on test-group B (radiographic and ultrasonographic tests). Thus, each group of doctors acted as a control group for the other. Changes in volume and rationality of requests were analysed. The number of requests decreased during the trial (p = 0.036). Request numbers decreased particularly for test-group A (p = 0.04). The proportion of requests that were non-rational decreased more in the intervention than in the control groups (p = 0.009). Rationality improved predominantly for test-group B (p = 0.043). Thus, routine feedback can change the quantity and quality of requests.

Diagnostic Services↗
PubMed2003

Visual feedback induces opposite effects on elementary centre of gravity and centre of pressure minus centre of gravity motions in undisturbed upright stance.

OBJECTIVE: To evaluate the instantaneous effects of visual feedback on undisturbed stance control mechanisms. DESIGN: The controlling variable, the centre of pressure trajectories, recorded using a force platform, were decomposed into two elementary motions: (1) the horizontal displacements of the centre of gravity and (2) the vertical projection of the difference between centre of pressure and the centre of gravity. These motions were processed through frequential analysis and modelled as fractional Brownian motion. BACKGROUND: Even though visual feedback protocols are advantageously used for rehabilitation purposes, their immediate effects from biomechanical and motor control points of view need to be assessed. METHODS: Twelve healthy adult subjects were tested through eyes open and visual feedback conditions. RESULTS: A significant amplitude increase in the difference between the centre of pressure and the centre of gravity motions and a decrease in the centre of gravity motions are observed during visual feedback. The fractional Brownian motion modelling analysis reveals an enhanced control of these elementary motions. The point at which the corrective process is initiated is increased with visual feedback whereas the time delay remains the same. CONCLUSIONS: The decrease of the centre of pressure displacements classically observed through visual feedback protocol initially results in a reduction of the centre of gravity motions and an augmentation of the difference between centre of pressure and centre of gravity motions, hence suggesting increased muscular activity. RELEVANCE: Precise knowledge of the effects generated by such feedback protocol should allow to optimise it as a rehabilitation tool.

Adult↗
PubMed2003

Brief motivational feedback improves post-incarceration treatment contact among veterans with substance use disorders.

OBJECTIVES: To test the efficacy of providing brief motivational feedback to increase post-incarceration substance use disorders (SUD) treatment contact. DESIGN: Randomized clinical trial (feedback vs. control) with a 2-month post-incarceration follow-up. PARTICIPANTS: Veterans (N = 73) incarcerated in a county jail system who met SUD diagnostic criteria. MEASURES: Baseline assessment included the Addiction Severity Index, the Form-90 assessment of recent alcohol use, and a DSM-IV SUD criteria checklist. The primary outcome was Veterans Administration (VA) appointments. Secondary outcomes were the Addiction Severity Index-Followup and the Treatment Services Review. INTERVENTION: All participants received baseline assessment. The feedback condition received personalized feedback and encouragement to explore ambivalence about change and treatment in a single interview. RESULTS: Participants receiving feedback were more likely to schedule appointments at a VA addictions clinic within 60 days of their jail release dates (67 vs. 41%; P < 0.03). Though differences were not statistically significant, more feedback participants attended addictions clinic appointments (47 vs. 32%; ns) and were retained in addictions treatment at 90 days (31 vs. 14%; P < 0.08). Treatment appointments were more likely when intervention occurred close to release. Loss of participants to post-release follow-up interviews was >50%, limiting power to detect significant differences by self-report. CONCLUSION: Brief motivational feedback shows promise as a way to link incarcerated individuals to SUD treatment services.

Feedback, Psychological↗
PubMed2003

Feedback based on patient evaluations: a tool for quality improvement?

Feedback regarding patient evaluations of health care is expected to be a tool for quality improvement. This study examined the response of general practitioners to such feedback in a randomised trial. Practitioners in the intervention group read and discussed the feedback report and then reported on a range of actions that can be undertaken to improve the quality of care. Their communication behaviour was not found to change. All of the practitioners were highly motivated to learn from patient views, both at baseline and after the intervention period. Compared to the control group, the practitioners in the intervention group had less favourable views of the relevance of patient feedback for their practice after the receipt of such feedback. Furthermore, these practitioners felt that a patient survey required considerable time and energy and saw little reason for change. Although patient feedback can help identify areas for improvement, specific barriers must be addressed before such feedback can be put to more widespread use.

Adult↗
PubMed1998

Effects of synthetic speech output and orthographic feedback on spelling in a student with autism: a preliminary study.

The effects of speech output and orthographic feedback on spelling performance were evaluated in this preliminary study. A nonspeaking student with autism was taught to spell words under three feedback conditions using a voice output communication aid. In the auditoryvisual condition, the participant received speech output and orthographic feedback. In the visual condition, the participant received only the orthographic feedback. In the auditory condition, the student received only speech output. An adapted alternating treatments design was used to evaluate the effects of the three feedback conditions. Although the participant reached criterion and maintained performance in each of the conditions, the provision of speech output alone and in combination with orthographic feedback resulted in more efficient spelling than the provision of orthographic feedback alone. Although replications with other subjects are necessary, findings suggest that speech output contributes to efficient spelling.

Achievement↗
PubMed1994

Reconciling competing motives in self-evaluation: the role of self-control in feedback seeking.

On the basis of the assumption that positive experiences enhance perceived ability to cope with the discomfort associated with negative performance feedback (NF), it was hypothesized that (a) positive experiences increase willingness to accept negative but useful feedback and that (b) individuals seek positive experiences before accepting NF. Experiment 1 found that past success increased Ss' interest in unrelated NF. Experiment 2 found that positive mood increased Ss' interest in NF. Experiment 3 investigated the amount of time Ss spent reading about their past success while waiting for new feedback. When the new feedback was mandatory, the time Ss spent reading about their past success increased with the anticipated negativity of the new feedback. However, when the new feedback was optional, the time Ss spent reading about their past success was an inverted-U function of the anticipated negativity of the new feedback. Results are discussed in terms of self-control processes.

Adaptation, Psychological↗
PubMed1994

Effects of feedback on the ability of asthmatic subjects to detect increases in the flow-resistive component to breathing.

Improved perception of increases in airflow resistance may have implications in asthma self-management. Two experiments that evaluated effects of feedback on the detection of flow-resistive loads are summarized. In the first experiment, detection ability of asthma patients who received feedback about the correctness of their responses in a signal-detection task was compared with that of asthma patients who did not receive feedback. Experiment 1 showed that subjects in the feedback condition detected the presence of flow-resistive loads more accurately than subjects in the no-feedback condition. In the second experiment, effects of feedback were compared between asthmatic and nonasthmatic subjects. Experiment 2 showed that effects of feedback training were equivalent in subjects with and without asthma.

Adolescent↗
PubMed2000

The impact of positive and negative feedback on reaction time in brain-damaged patients.

Little is known about the impact of feedback on the reaction times (RTs) of brain-damaged (BD) patients. The authors therefore investigated the effect of positive and negative feedback on these patients, using a 4-choice RT task. Participants were 107 BD patients with different etiologies and 50 orthopedic (OG) control patients. Patients were assigned to 3 groups in which performance-independent negative, positive, and no feedback were given. Statistical analysis showed that negative feedback led to significantly shorter RTs in BD patients. Even BD patients with high depression scores were affected by negative feedback. In contrast, negative feedback had no impact on the RTs of the OG controls, and positive feedback had no influence on the RTs of any group. These results raise some interesting questions about motivational processes in BD patients.

Adolescent↗
PubMed2005

Goal regulation across time: the effects of feedback and affect.

This research focused on the processes individuals use to regulate their goals across time. Two studies examined goal regulation following task performance with 6 samples of participants in a series of 8-trial task performance experiments. The experiments involved: (a) 3 task types, (b) 2 goal types, and (c) actual or manipulated performance feedback referring to the focal participant's own performance or to the participant's performance compared with others' performance. Applying multilevel methods, the authors examined (a) how performance feedback influences subsequent goals within individuals across both negative and positive performance feedback ranges, and (b) the mediating role of affect in explaining the relationship between feedback and subsequent goal setting. Results showed that participants adjusted their goals downwardly following negative feedback and created positive goal-performance discrepancies by raising their goals following positive feedback. In each sample, affect mediated substantial proportions of the feedback-goals relationship within individuals.

Achievement↗
PubMed1999

Can a standardized needs assessment be used to improve the care of people with severe mental disorders? A pilot study of 'needs feedback'.

The care programme approach (CPA) was introduced in the United Kingdom in 1991 to ensure that the needs of people with mental health problems are met appropriately. Many community psychiatric nurses (CPNs) act as 'key workers' under the CPA. Recent evidence suggests that the CPA is not particularly effective at meeting the needs of this vulnerable group, but it might be possible to enhance the CPA by introducing a more 'needs-led' approach to the planning of nursing care. 'Needs feedback' is a technique for enhancing the CPA. Needs feedback begins with a standardized assessment of patients' psychiatric and social needs by a nurse specialist. The patient's CPN is then provided with information on: (a) the needs identified; (b) why these needs have been identified; (c) the interventions required to meet the identified needs; and (d) how these interventions may be obtained. In the pilot study reported in this paper, 20 patients with severe mental disorder were evaluated before and after their CPN received needs feedback. All patients were living in the community and being managed by CPNs under the CPA. Outcome was assessed 6 months after the feedback in terms of: mental state, social behaviour and number of 'unmet' needs. Needs feedback was found to be compatible with the CPA in that it proved acceptable to CPNs and patients. Significant improvements were seen in the number of 'unmet' needs and the level of anxious/depressive symptoms. Improvements approaching significance were seen for social functioning and negative psychiatric symptoms, but not for positive psychiatric symptoms. This pilot study suggests that needs feedback may improve the quality of nursing assessment and care planning within the CPA. Further controlled investigations of needs feedback are justified.

Adult↗
PubMed1999

Differential regulation of hippocampal glucocorticoid receptors mRNA and fast feedback: relevance to post-traumatic stress disorder.

Hippocampal glucocorticoid receptors (GR and MR) play an important role in glucocorticoid negative feedback. Abnormalities in negative feedback are found in depression and in post-traumatic stress disorder (PTSD), suggesting that GR and MR might be involved in the pathophysiology of these disorders. Enhanced negative feedback, the PTSD-specific neuroendocrine abnormality, can be induced in animals using a single prolonged stress (SPS) paradigm (a number of different stressors in one prolonged session, 'no stress' interval and a testing session one week later). In the current study, we examined hippocampal GR and MR mRNA distribution in the same animals that exhibited altered negative feedback following the SPS. Seven groups of adult Sprague-Dawley male rats (seven animals each) were used in two studies, comparing unstressed controls to acutely stressed animals (SPS: 24 h group), SPS animals (seven and 14 days), and SPS + chronic stress animals. GR and MR mRNA distribution across hippocampal subfields was studied using in-situ hybridization with 35S-labelled cRNA probes. Acute stress produced down-regulation of GR and MR mRNA across all hippocampal subfields. Seven days later (SPS-7 group), there was a differential recovery, with GR mRNA reaching higher than the prestress levels, and MR mRNA remaining down-regulated. The same differential regulation was present in the 14-day group. Chronically stressed animals that exhibited normal fast feedback also had normalization in their GR and MR mRNA levels. The MR/GR ratio was decreased only in animals that had enhanced fast feedback. These findings suggest that the increase in GR, in hippocampus is involved in the fast feedback hypersensitivity observed in the SPS animals, and might also underlie enhanced dexamethasone sensitivity found in PTSD. Since differential activation of GR and MR can modulate memory, behavioural responsivity, anxiety and fear, change in MR/GR ratio might also explain other PTSD-related phenomena.

Animals↗
PubMed2001

Impact of patient feedback on the interpersonal skills of general practice registrars: results of a longitudinal study.

CONTEXT: A general practice vocational training program. OBJECTIVES: To examine the impacts and implications of different models of systematic patient feedback on the development of general practice (GP) registrars' interpersonal skills as they progressed through a GP vocational training program. DESIGN: A longitudinal study in which GP registrars were randomly assigned to three models of patient feedback: a control group and two intervention groups. The major source of data gathering was through the Doctors' Interpersonal Skills Questionnaire (DISQ) which was administered to patients immediately after their consultation. SUBJECTS: 210 GP registrars, 104 GP supervisors and 28 156 patients. RESULTS: Multivariate analysis techniques (including repeated-measures analysis) tested the effectiveness of the interventions. Findings showed that systematic patient feedback at regular intervals throughout GP training resulted in sustained levels of interpersonal skills. The most significant gains in interpersonal skills for both intervention groups occurred in the earlier stages of general practice training. Most registrars found the experience of patient feedback useful for gaining a better understanding of their interpersonal skills and for identifying areas in which they needed to improve. GP supervisors valued the opportunity to receive patient feedback themselves and found the activity a useful adjunct to their preceptor role. CONCLUSIONS: Patients, by providing feedback on doctors' interpersonal skills, have been able to contribute to improving the quality of the patient-doctor interaction. GP registrars and their supervisors value highly the role of patient feedback in interpersonal skill development.

Adult↗
PubMed1997

Enhanced performance feedback to strengthen biofeedback treatment outcome with childhood migraine.

Recent research has indicated that both the magnitude and frequency of performance feedback may be important variables in the biofeedback treatment of headaches. The purpose of this research was to determine whether the qualitative and/or quantitative enhancement of performance feedback could improve the efficacy of thermal biofeedback as a treatment for childhood migraine. In a time-lagged control design, six children with migraine headaches were exposed to thermal biofeedback training and then provided performance feedback reflecting moderate and high success, and, if needed, increased feedback frequency. In four of six subjects, clinically significant reductions in headache activity corresponded directly with the addition of feedback suggesting marked improvement in handwarming relative to peers, even when no improvement in handwarming had actually occurred. In two other subjects, clinically significant changes in headache activity were reported only after performance feedback frequency was increased. The results support the importance of attending to both qualitative and quantitative parameters of feedback as well as skill acquisition during thermal biofeedback treatment of children with migraine.

Adolescent↗
PubMed1992

Metabolic feedback in mammalian endocrine systems.

Information processing through feedback loops is an integral part of most endocrine systems, and ranges from simple negative loops to complex combinations of negative and positive loops. Moreover, feedback may occur at local (paracrine) or long-distance sites, and with multiple time-domains. Traditionally, feedback is visualized as one hormone stimulating release of a second hormone, which then circulates in the blood to carry out various biological activities, one of which is to inhibit further secretion of the first hormone. This represents a fail-safe mechanism to protect the organism against the potentially damaging effects of uncontrolled secretion of many of the common hormones, some of which are highly catabolic or anabolic. However, it is becoming increasingly apparent that the products of catabolism and anabolism may themselves participate in the feedback process in either a feed-forward or feedback manner. For example, free fatty acids are liberated by the action of growth hormone, and in turn are potent inhibitors of growth hormone secretion (feedback). On the other hand, stress activates adrenal cortical and medullary secretion, which also promotes lipolysis, but in this case the liberated free fatty acids may actually stimulate the system further (feed-forward). Similarly, glucose has been shown to directly inhibit the activity of several different endocrine pathways, and must now be considered an integral part of the overall regulatory mechanism involved in fine-tuning secretion and possibly production of hormones. By constructing models of feedback of increasing complexity, it is possible to make predictions about previously unrecognized relationships between hormones and products of metabolism.

Animals↗
PubMed2003

Effect of an infection control program using education and performance feedback on rates of intravascular device-associated bloodstream infections in intensive care units in Argentina.

OBJECTIVE: Our aim was to ascertain the effect of an infection control program, using education and performance feedback on intensive care units, for intravascular device (IVD)-associated bloodstream infection (BSI). METHODS: Within 4 level III, adult, intensive care units in Argentina, all admitted, adult patients with a central vascular catheter in place for at least 24 hours were included. This was a prospective before-and-after trial in which rates of IVD-associated BSI determined during a period of active surveillance without education or performance feedback (phase 1) were compared after sequential implementation of an infection control program using education (phase 2) and performance feedback (phase 3). RESULTS: A total of 1219 IVD days were accumulated in phase 1; 586 during phase 2; and 4140 during phase 3. Compliance with central vascular catheter--site care improved significantly from baseline during the study period. Overall rates of IVD-associated BSI were lowered significantly from baseline after sequential implementation of education and performance feedback (11.10 vs 46.63 BSI/1000 IVD days; relative risk=0.25; 95% confidence interval=0.17-0.36; P<.0001). Rates of IVD-associated BSI decreased significantly after implementation of an educational program (phase 1 to phase 2) (relative risk 0.37; confidence interval 0.19-0.73; P=.0026) and further reductions were seen after implementation of a performance feedback program (phase 2 to phase 3), although the reduction did not reach statistical significance (9.9 vs 17.06 BSI/1000 IVD days; relative risk 0.58; confidence interval 0.29-1.18; P=.11). Additional analysis of the data using chi2 for trends demonstrated that sequential implementation of an education and performance feedback program resulted in a significant trend toward reduced rates of IVD-associated BSI (P<.001). CONCLUSION: Implementation of an infection control program, using education and performance feedback, resulted in significant reductions in rates of IVD-associated BSI.

Aged↗
PubMed2005

A positive feedback loop of phosphodiesterase 3 (PDE3) and inducible cAMP early repressor (ICER) leads to cardiomyocyte apoptosis.

cAMP plays crucial roles in cardiac remodeling and the progression of heart failure. Recently, we found that expression of cAMP hydrolyzing phosphodiesterase 3A (PDE3A) was significantly reduced in human failing hearts, accompanied by up-regulation of inducible cAMP early repressor (ICER) expression. Angiotensin II (Ang II) and the beta-adrenergic receptor agonist isoproterenol (ISO) also induced persistent PDE3A down-regulation and concomitant ICER up-regulation in vitro, which is important in Ang II- and ISO-induced cardiomyocyte apoptosis. We hypothesized that interactions between PDE3A and ICER may constitute an autoregulatory positive feedback loop (PDE3A-ICER feedback loop), and this loop would cause persistent PDE3A down-regulation and ICER up-regulation. Here, we demonstrate that ICER induction repressed PDE3A gene transcription. PDE3A down-regulation activated cAMP/PKA signaling, leading to ICER up-regulation via PKA-dependent stabilization of ICER. With respect to Ang II, the initiation of the PDE3A-ICER feedback loop depends on activation of Ang II type 1 receptor (AT1R), classical PKC(s), and CREB (cAMP response element binding protein). We further show that the PDE3A-ICER feedback loop is essential for Ang II-induced cardiomyocyte apoptosis. ISO and PDE3 inhibitors also induced the PDE3A-ICER feedback loop and subsequent cardiomyocyte apoptosis, highlighting the importance of this PDE3A-ICER feedback loop and cAMP signaling in cardiomyocyte apoptosis. Our findings may provide a therapeutic paradigm to prevent cardiomyocyte apoptosis and the progression of heart failure by inhibiting the PDE3A-ICER feedback loop.

3',5'-Cyclic-AMP Phosphodiesterases↗