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At least 235 records · Page 13Linked to original sources
PubMed2002

Spine needle biopsy simulator using visual and force feedback.

OBJECTIVE: Biopsy with an inserted needle is an important procedure for lesion detection in the spine, but is difficult to perform due to the presence of many critical organs near the spine. This article presents a spine needle biopsy simulator, based on visual and force feedback, which can be used to plan the optimal path of a needle and to practice the procedure without risk. MATERIALS AND METHODS: The simulator is composed of a 3D human model, a visual-feedback component, a force-feedback component, and an evaluation module. The human model is based on 3D CT data. The visual-feedback component provides an oblique section, multiplanar reformatting images, and a volume-rendered image. Of these, the oblique section display is very useful for planning a 3D path for the needle. During simulation, the force-feedback component generates and provides realistic forces acting on the biopsy needle in real time by synchronizing them to visual feedback. After each simulation, the evaluation module provides a performance analysis for the trainee. RESULTS: For an XCT abdomen volume data set of 256 x 256 x 256, the update rate of image rendering due to needle movement is over 25 Hz, with a force-feedback rate of 1 kHz. This performance proved to be good enough for the trainee to learn the relationship between visual and force feedback. CONCLUSIONS: The simulator is useful for the planning of and training in complicated 3D spine needle biopsy procedures. It may be used as an educational tool for beginners, a practice tool to increase expertise, or a test bed for new procedures.

Algorithms↗
PubMed2005

Feedback in psychotherapy.

Feedback is defined as a response to an action that shapes or adjusts that action in subsequent performance. Though its pervasiveness in human behavior is noted, feedback in clinical practice is a deliberate psychological intervention that has two essential functions, information and influence. Feedback can be descriptive, evaluative, emotional, and interpretive. The role of feedback in promoting change through interpersonal influence and the role of resistance in the feedback process are discussed. We present practical examples and suggestions for maximizing the effectiveness of feedback and responding therapeutically to resistance. Current outcome research on feedback as a major component of treatment is reviewed and discussed. Implications of the feedback literature for practice are provided.

Feedback, Psychological↗
PubMed1996

Growth rate-dependent control, feedback regulation and steady-state mRNA levels of the threonyl-tRNA synthetase gene of Escherichia coli.

The expression of the gene thrS encoding threonyl-tRNA synthetase is under the control of two apparently different regulatory loops: translational feedback regulation and growth rate-dependent control. The translational feedback regulation is due to the binding of threonyl-tRNA synthetase to a site located in the leader RNA of thrS, upstream of the initiation codon, which mimics the anticodon stem and loop of tRNA(Thr). This binding competes with that of the ribosome and thus inhibits translation initiation. Here, we investigate the mechanism of growth rate-dependent control, i.e. the mechanism by which the synthetase accumulates at high growth rates. We show that growth rate-dependent control acts at the level of translation and requires feedback regulation since mutations that abolish feedback regulation also abolish growth rate-dependent control. We also show that tRNA(Thr), which accumulates at high growth rates, is one of the effectors of growth rate-dependent control since its accumulation can cause derepression independently of growth rate. We show that this tRNA(Thr)-dependent derepression is also dependent on feedback regulation since mutations which abolish feedback also prevent derepression. Based on these results and previous data concerning the mechanism of translational feedback regulation, we propose that threonyl-tRNA synthetase growth rate-dependent control is the consequence of the accumulation at high growth rates of two effectors, the ribosome and tRNA(Thr). We also study the growth rate-dependence of the steady state level of thrS mRNA and show that the steady state level of thrS mRNA increases at high growth rates. This increase is dependent on the translational feedback regulation and can also be detected, independently of growth rate, when thrS mRNA translation is derepressed. Consistently with the model of growth rate-dependent control above, we propose that at high growth rates, the mRNA is well translated and thus stabilised and that, at low growth rates, because of its low translation, thrS mRNA is rapidly degraded.

Base Sequence↗
PubMed2001

Robust oscillations within the interlocked feedback model of Drosophila circadian rhythm.

A mechanism for generating circadian rhythms has been of major interest in recent years. After the discovery of per and tim, a model with a simple feedback loop involving per and tim has been proposed. However, it is recognized that the simple feedback model cannot account for phenotypes generated by various mutants. A recent report by Glossop, Lyons & Hardin [Science286, 766 (1999)] on Drosophila suggests involvement of another feedback loop by dClk that is interlocked with per-tim feedback loop. In order to examine whether interlocked feedback loops can be a basic mechanism for circadian rhythms, a mathematical model was created and examined. Through extensive simulation and mathematical analysis, it was revealed that the interlocked feedback model accounts for the observations that are not explained by the simple feedback model. Moreover, the interlocked feedback model has robust properties in oscillations.

Animals↗
PubMed1975

Effects of immediacy of feedback and level of aspiration statements on learning tasks for delinquent youngsters.

The performance of institutionalized delinquent youngsters on paired associate learning tasks was investigated to determine whether level of aspiration (LOA) statements were associated with improved performance under varying feedback conditions. The effects of the feedback conditions were also examined. Forty-eight male adolescents were randomly assigned to the following six treatment conditions: (1) Delayed Feedback, (2) Delayed Feedback with LOA, (3) Immediate Feedback, (4) Immediate Feedback with LOA, (5) No Feedback, (6) No Feedback with LOA. The LOA conditions produced significantly better performance than did the no-LOA conditions. Implications for curricular intervention are discussed.

Achievement↗
PubMed1986

Ocular and stabilization feedback: an evaluation of two EMG biofeedback control procedures.

This study evaluated the adequacy of two novel EMG biofeedback control procedures. During a single training session, 36 subjects received either contingent EMG feedback from the frontal region (Veridical), contingent feedback for vertical eye movements (Ocular), or a feedback condition where the signal increased with deviations in any direction from baseline EMG levels (Stabilization). The results supported the use of Ocular but not Stabilization feedback as a control procedure in frontalis EMG biofeedback studies. Ocular feedback did not produce reductions in frontalis EMG but did lead to changes in subjective measures of nonspecific treatment effects that were at least comparable to those obtained with Veridical feedback. Stabilization subjects produced small but significant reductions in EMG, felt the most bored as a result of their feedback training, and were the most likely to rate themselves as having received false feedback. The implications of attribution theory and multiprocess relaxation theory for the evaluation of nonspecific treatment effects are discussed.

Adolescent↗
PubMed1994

Effects of dietary fat feedback on behavioral and psychological variables.

This paper reports on the immediate and delayed reactions to dietary fat consumption feedback. Subjects in our study received (1) personalized dietary fat feedback and (2) information about how to alter their fat consumption. Fat consumption was measured using a brief fat assessment instrument. Subjects were categorized into three risk groups: at or below, above, and significantly above the recommended level. Emotional, cognitive, and behavioral reactions were measured immediately after receiving feedback and at 1 month postfeedback. Subjects who received high fat feedback showed greater negative emotional distress in response to the feedback and stated that they knew less about high-fat foods than subjects receiving lower feedback. By the 1-month follow-up, subjects in the highest feedback condition were least likely to report intentions to lower their dietary fat. Interventions designed to alter dietary fat consumption should take into account the emotional and cognitive consequences of risk factor feedback.

Adolescent↗
PubMed2004

Visual feedback alters the variations in corticospinal excitability that arise from rhythmic movements of the opposite limb.

Augmented visual feedback can have a profound bearing on the stability of bimanual coordination. Indeed, this has been used to render tractable the study of patterns of coordination that cannot otherwise be produced in a stable fashion. In previous investigations (Carson et al. 1999), we have shown that rhythmic movements, brought about by the contraction of muscles on one side of the body, lead to phase-locked changes in the excitability of homologous motor pathways of the opposite limb. The present study was conducted to assess whether these changes are influenced by the presence of visual feedback of the moving limb. Eight participants performed rhythmic flexion-extension movements of the left wrist to the beat of a metronome (1.5 Hz). In 50% of trials, visual feedback of wrist displacement was provided in relation to a target amplitude, defined by the mean movement amplitude generated during the immediately preceding no feedback trial. Motor potentials (MEPs) were evoked in the quiescent muscles of the right limb by magnetic stimulation of the left motor cortex. Consistent with our previous observations, MEP amplitudes were modulated during the movement cycle of the opposite limb. The extent of this modulation was, however, smaller in the presence of visual feedback of the moving limb (FCR omega2=0.41; ECR omega2=0.29) than in trials in which there was no visual feedback (FCR omega2=0.51; ECR omega2=0.48). In addition, the relationship between the level of FCR activation and the excitability of the homologous corticospinal pathway of the opposite limb was sensitive to the vision condition; the degree of correlation between the two variables was larger when there was no visual feedback of the moving limb. The results of the present study support the view that increases in the stability of bimanual coordination brought about by augmented feedback may be mediated by changes in the crossed modulation of excitability in homologous motor pathways.

Adult↗
PubMed2002

Detailed postal feedback about prescribing to asthma patients combined with a guideline statement showed no impact: a randomised controlled trial.

OBJECTIVE: To evaluate the effects of postal feedback with clinically relevant data on general practitioners' prescribing compared with feedback with aggregate data on prescribing patterns of asthma drugs. METHODS: The study was a randomised, controlled trial. The general practitioners (GPs) in the County of Funen, Denmark (292 GPs representing 178 practices) were randomised to one of three groups receiving different forms of prescriber feedback. The first group received detailed and clinically relevant data on asthma drug prescribing patterns and a guideline statement. These data included tables with counts of asthma patients following classification of each individual's consumption of inhaled beta2-agonists and use of inhaled steroids. The second group received aggregate data on asthma drug prescribing patterns and a guideline statement, and the third group received feedback on an unrelated subject and served as control for the other groups. Each GP received prescriber feedback three times within a 6-month period. The last two letters with prescriber feedback had updated information with the purpose of showing changes in prescribing patterns. Effects were followed for a period of 1 year. The main outcome measures were change in fraction of asthmatics treated with inhaled steroids and incidence rate of treatment with inhaled steroids. RESULTS: The three groups had similar baseline characteristics. None of the two types of feedback on prescribing of asthma drugs had a statistically significant impact on GPs' prescribing patterns. CONCLUSION: Mailed prescriber feedback of detailed and clinically relevant data with a guideline statement, without revealing patient identities, has little or no impact on prescribing patterns.

Adolescent↗
PubMed1987

Effect of antigen priming on T-cell suppression. I. Activity of Ly 1+2+ feedback suppressor T-cell precursors after isolation from competing Ly 2-T cells.

Previous experiments have demonstrated that feedback suppression of murine antibody responses occurs in vitro after exposure of unprimed T-cell subsets to suppression-inducing signals from primed cells, resulting in suppression of primary and secondary IgM as well as IgG anti-SRBC responses. However, following priming with antigen when cells appear which are capable of inducing feedback suppression, the ability of unfractionated splenic T-cell populations to mediate detectable feedback suppression in vitro rapidly disappears, suggesting that priming alters the expression of feedback suppression at the same time as providing for its induction. In the present study, we have succeeded in isolating active feedback suppressor T-cell precursors (preTs) in the Ly 1+2+ and L3T4- T-cell populations from SRBC-primed as well as from unprimed mice, demonstrating that preTs are not lost after priming. The preTs isolated from primed mice resemble those isolated from unprimed mice in Ly and L3T4 phenotype, cell dose requirements, kinetics, level of suppression, and requirement for in vitro activation by primed cells. These results imply that antigen priming neither significantly depresses nor enhances the ability of Ly 1+2+ preTs to participate in feedback suppression and that activated suppressor effector cells are not detectable in the Ly 1+2+ splenic T-cell subset. Priming does, however, induce an enhancing activity in Ly 2-, L3T4+ T cells which appears to compete with feedback suppression and thus may account for the absence of detectable feedback suppression when unfractionated T cells from primed mice are the only source of preTs.

Animals↗
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↗
PubMed1995

Normal glucocorticoid fast feedback following chronic 50% corticosterone pellet treatment.

Rapid effects of glucocorticoids on adrenocorticotropin hormone (ACTH) secretion were first demonstrated by Dallman and Jones. Glucocorticoid fast feedback is believed to be dependent upon brain feedback sites, particularly the hippocampus. The current studies are part of a series of studies examining the links between hippocampal adrenal steroid receptor changes and changes in fast feedback. Our previous studies have demonstrated that chronic stress and chronic corticosterone injections are capable of diminishing the fast feedback effect of injected glucocorticoids on ACTH secretion. The current studies explore whether administration of a different form of exogenous corticosterone, a 50% corticosterone pellet, a treatment that leads to constant corticosterone levels of 7-8 micrograms/dl, was capable of affecting fast feedback. Rats were studied both before and after the implantation of the 50% corticosterone pellets. Administration of cortisol at the initiation of restraint stress resulted in decreased ACTH release over the course of 30 min in both the morning and afternoon before implantation of corticosterone pellets. Following the implantation of 50% corticosterone pellets, the overall ACTH stress response was diminished in both the morning and the afternoon. However, cortisol injection at the initiation of restraint stress continued to exert fast feedback effects on ACTH secretion. These studies suggest that constant low plasma corticosterone concentrations of 6-7 micrograms/dl are able to inhibit the overall stress response but not the ability to respond to fast feedback. This contrasts with our previous studies with a corticosterone injection paradigm which produced abnormalities in glucocorticoid fast feedback.

Adrenocorticotropic Hormone↗
PubMed2006

Event-related fMRI of category learning: differences in classification and feedback networks.

Eighteen healthy young adults underwent event-related (ER) functional magnetic resonance imaging (fMRI) of the brain while performing a visual category learning task. The specific category learning task required subjects to extract the rules that guide classification of quasi-random patterns of dots into categories. Following each classification choice, visual feedback was presented. The average hemodynamic response was calculated across the eighteen subjects to identify the separate networks associated with both classification and feedback. Random-effects analyses identified the different networks implicated during the classification and feedback phases of each trial. The regions included prefrontal cortex, frontal eye fields, supplementary motor and eye fields, thalamus, caudate, superior and inferior parietal lobules, and areas within visual cortex. The differences between classification and feedback were identified as (i) overall higher volumes and signal intensities during classification as compared to feedback, (ii) involvement of the thalamus and superior parietal regions during the classification phase of each trial, and (iii) differential involvement of the caudate head during feedback. The effects of learning were then evaluated for both classification and feedback. Early in learning, subjects showed increased activation in the hippocampal regions during classification and activation in the heads of the caudate nuclei during the corresponding feedback phases. The findings suggest that early stages of prototype-distortion learning are characterized by networks previously associated with strategies of explicit memory and hypothesis testing. However as learning progresses the networks change. This finding suggests that the cognitive strategies also change during prototype-distortion learning.

Brain↗
PubMed2006

The good, the bad and the neutral: electrophysiological responses to feedback stimuli.

The feedback error-related negativity (fERN) is a component of the event-related brain potential elicited in gambling and trial-and-error learning tasks by negative, but not positive, feedback stimuli. Here, we present the results of a series of five experiments that investigated the response of the fERN to the presentation of neutral feedback stimuli. In three of the experiments, the neutral feedback stimuli indicated that the participants did not receive a potential reward nor incur a potential penalty (i.e., they received nothing); and in the remaining two experiments, the neutral feedback stimuli did not convey any meaningful information (i.e., the participants were either successful or unsuccessful on those trials, but the feedback stimuli were uninformative about the outcomes). Across the five experiments, we found that neutral feedback stimuli elicited a fERN about as large as that elicited by negative feedback stimuli. This result is consistent with recent proposals that the evaluative system that produces the fERN classifies outcomes into two categories: those outcomes that indicate that a goal has been satisfied and those that do not.

Adult↗
PubMed2006

Regulatory dynamics of synthetic gene networks with positive feedback.

Biological processes are governed by complex networks ranging from gene regulation to signal transduction. Positive feedback is a key element in such networks. The regulation enables cells to adopt multiple internal expression states in response to a single external input signal. However, past works lacked a dynamical aspect of this system. To address the dynamical property of the positive feedback system, we employ synthetic gene circuits in Escherichia coli to measure the rise-time of both the no-feedback system and the positive feedback system. We show that the kinetics of gene expression is slowed down if the gene regulatory system includes positive feedback. We also report that the transition of gene switching behaviors from the hysteretic one to the graded one occurs. A mathematical model based on the chemical reactions shows that the response delay is an inherited property of the positive feedback system. Furthermore, with the aid of the phase diagram, we demonstrate the decline of the feedback activation causes the transition of switching behaviors. Our findings provide a further understanding of a positive feedback system in a living cell from a dynamical point of view.

Escherichia coli↗
PubMed2006

Separating brain regions involved in internally guided and visual feedback control of moving effectors: an event-related fMRI study.

Online visual information of moving effectors plays important roles in visually guided movements. The present study used event-related functional resonance imaging to temporally separate neural activity associated with internally guided and visual feedback control of moving effectors. Using a cursor controlled by a computer mouse, participants traced curved lines on a screen. During this movement, vision of the moving cursor was occluded after tracing had begun and then was restored after variable intervals. The results showed that when visual feedback was unavailable, bilateral activation was significantly greater in the basal ganglia, thalamus, premotor cortex and mesial motor areas, peaking at the presupplementary motor area (pre-SMA). In contrast, when visual feedback was available, significantly greater activation was observed bilaterally in the posterior parietal cortex (PPC) and cerebellum and in the middle and inferior frontal gyri and occipito-temporal cortex in the right hemisphere. Pre-SMA activity was significantly negatively correlated with tracing error when visual feedback was unavailable. In contrast, right PPC activation showed a significant positive correlation with tracing error after visual feedback became available. These findings suggest that the pre-SMA is involved in internally guided movements in the absence of visual feedback, and that the PPC is related to visual feedback control by evaluating online visuomotor error. The current study clarifies the different functional roles of fronto-parietal and cerebellum circuits subserving visually guided movements regarding visual feedback control of effectors.

Adult↗
PubMed2000

Sensorimotor synchronization: the impact of temporally displaced auditory feedback.

When subjects are asked to tap in synchrony to a regular sequence of stimulus events (e.g., clicks), performance is not perfect in that, usually, an anticipation of the tap is observed. The present study examines the influence of temporally displaced auditory feedback on the size of this anticipatory error. Whereas earlier studies have shown that this asynchrony exhibits a linear increase in size as a function of an increasing delay in such additional auditory feedback, this study compared the impact of shifting feedback forward in time (i.e., feedback presented before the tap) with that of delayed auditory feedback. Results showed that the impact of feedback displacement on the amount of asynchrony differed for positive and negative displacements. Delayed feedback led to an increase in asynchrony, whereas negative displacements had (almost) no effect. This finding is related to a model assuming that the various feedback components arising from the tap (tactile, kinesthetic, auditory) are integrated to form one central representation, and that the timing of this central representation arises from a linear combination of the components involved.

Acoustic Stimulation↗
PubMed1996

Type II (glucocorticoid) receptors mediate fast-feedback inhibition of the hypothalamic-pituitary-adrenal axis in man.

The hypothalamic-pituitary-adrenal axis is inhibited via negative feedback, which in rats is mediated via type I and II steroid receptors. Although these receptors are present in neural tissue in man, their respective roles have not been systematically examined. Fast-feedback is the first component of negative feedback, occurs within two hours, and is sensitive to the rate of rising cortisol levels. This study examines the role of type I & II steroid receptors in mediating fast-feedback. A within subjects design was used. Subjects were pre-treated with placebo, spironolactone 200mg or RU486 (mifepristone)-type I & II antagonists respectively. This was followed by infusion of either placebo or hydrocortisone. 8 healthy male volunteers were studied on four separate occasions. Plasma cortisol and ACTH were measured by RIA. Significant elevations of morning basal ACTH and Cortisol following RU 486 relative to placebo or spironolactone were observed. ACTH responses to hydrocortisone (i.e. feedback) were not altered by prior administration of spironolactone. In contrast, RU 486 pre-treatment resulted in a significant attenuation of fast-feedback. These results indicate that type II receptors mediate the fast-feedback phase of negative feedback in man.

Adrenal Glands↗