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At least 955 records · Page 53Linked to original sources
PubMed1994

Long-term effects of auditory feedback training on relearned symmetrical body weight distribution in stroke patients. A follow-up study.

Long-term effects of auditory kinetic feedback on relearned symmetrical body weight distribution while rising and sitting down were studied in stroke patients. Thirty patients were re-tested on average 33 months after having trained with and without auditory feedback. Body weight distribution on the legs was measured with two force plates. At re-test there was a decrease from 48% to 39% of body weight distribution (%BWD) on the paretic leg in rising and in sitting down in the patients in the auditory feedback group (p < 0.001). In the control group the decrease was from 44 to 39% BWD on the paretic leg (p < 0.05) in rising and from 44 to 42% BWD (n.s.) in sitting down. The symmetrical body-weight distribution, acquired after auditory feedback training, was not consistent over time. Movement time, however, was significantly reduced in the auditory feedback group (p < 0.05). Possible reasons for the findings are discussed.

Aged↗
PubMed1996

Different balance of excitation and inhibition in forward and feedback circuits of rat visual cortex.

Different cortical areas are linked reciprocally via forward and feedback connections. Forward connections are involved in the representation of retinal images, whereas feedback pathways may play a role in the selection and interpretation of visual information. To examine the synaptic mechanisms of forward and feedback connections between primary and secondary visual cortical areas directly, we have performed intracellular recordings in slices of rat visual cortex. Irrespective of stimulus intensity and membrane potential, 78% (45/58) of the cells in striate cortex activated by feedback input showed monosynaptic responses that were depolarizing only, and inhibitory inputs were evident merely as a slight acceleration in the decay of EPSPs. In contrast, in 89% (17/19) of the cells, stimulation of forward input evoked monosynaptic excitatory postsynaptic potentials (EPSPs), followed by disynaptic, hyperpolarizing inhibitory postsynaptic potentials (IPSPs). EPSPs followed by IPSPs also were recorded after stimulation of local connections within primary visual cortex (92%, 12/13) and after activation of thalamocortical input (91%, 10/11). These results suggest that the synaptic organization of feedback connections are distinct from forward, local, and thalamocortical circuits. The findings further indicate that intracortical back projections exert modulatory influences via synaptic mechanisms in which weak inhibitory input is strongly dominated by excitation.

Animals↗
PubMed1996

Auditory feedback regulation of perturbed stance in stroke patients.

The effect of auditory input on impaired postural control perturbations was evaluated in two groups of stroke patients participating in a rehabilitation programme after a recent (< 12 months) and single episode of stroke, or less recent (> 12 months), and multiple episodes of stroke. Auditory input took the form of feedback signals generated by the forces actuated by the feet on a force platform in response to the patient's postural movements. Vibratory stimuli applied to the calf muscles induced sudden perturbations which the patients had to counteract to maintain an upright stance. The effect of auditory feedback in facilitating the maintenance of stance was measured in terms of sagittal torque variance (body sway) recorded on a force platform. In the presence of auditory feedback, body torque variance in response to perturbed posture was significantly reduced in the recent stroke group, whereas in the less recent stroke group the auditory feedback did not prove effective. Moreover, learning seems essential to utilize the auditory feedback.

Acoustic Stimulation↗
PubMed1997

Feedback to nurse managers about staff nurses' perceptions of their jobs.

This article describes a survey feedback intervention in which staff nurses were surveyed about various job characteristics, job satisfaction, and intent to remain in the organization. Nurse managers received the feedback through graphs and a workshop. A year later the same survey was conducted, and the results were compared with preintervention data. Of the 13 units surveyed, six showed significant improvement in one area and one showed significant improvement in 11. Nurse managers considered the survey feedback helpful, but the feedback alone was not sufficient for achieving broad changes in 1 year. However, the feedback is a useful component of continuous quality improvement efforts.

Attitude of Health Personnel↗
PubMed2003

A data glove with tactile feedback for FMRI of virtual reality experiments.

Virtual reality (VR) technology is increasingly recognized as a useful tool for the assessment and rehabilitation of neurologic and psychiatric disorders. The hope that VR can accurately mimic real-life events is also of great interest in basic neuroscience, to identify the brain activity that underlies complex behavior by combining VR with techniques such as functional magnetic resonance imaging (fMRI). Toward these applications, in this study we designed and validated an fMRI-compatible data glove with a built-in vibratory stimulus device for tactile feedback during VR experiments. A simple VR-fMRI experiment was performed at 3.0 Tesla on four young healthy adults involving touching a virtual object with and without tactile feedback. The usefulness of the data glove was subsequently assessed using a series of questionnaires, behavioral performance, and the resulting activation images. Questionnaire scores indicated positive opinions with respect to the data glove, the tactile feedback, and the experimental paradigm. All subjects felt comfortable in the scanner during the VR experiment and were able to perform all aspects of the tasks successfully and with reasonable accuracy. In addition, activation maps showed the anticipated modulations in motor, somatosensory, and parietal cortex. These results support that tactile feedback enhances the realism of virtual hand-object interactions, and that the tactile data glove is suitable for use in other VR-fMRI research applications (e.g., VR physical therapy for stroke recovery).

Adult↗
PubMed1993

Reflectance feedback control of photocoagulation in vivo.

OBJECTIVE: The objective of this research was to build a real-time feedback system that controlled lesion size. Two-dimensional reflectance images were acquired with a charge-coupled device camera during irradiation, and argon laser exposure was ended when parameters of the image reached prespecified values. METHODS: The real-time feedback control system was tested by creating lesions at different power levels in pigmented rabbits. Laser exposure time was controlled by monitoring the central reflectance. RESULTS: Results of feedback-controlled lesions formed in vivo in pigmented rabbits are presented. An ability to produce uniform lesions despite variation in tissue absorption or changes in laser power is demonstrated. CONCLUSIONS: Reflectance control of photocoagulation is possible; incorporation of feedback during photocoagulation has numerous therapeutic and safety benefits over current ballistic delivery.

Animals↗
PubMed1975

Feedback of true heart rate during exposure in vivo.

Ten women with specific chronic animal phobias were treated by graded exposure in vivo in two to four two-hour treatment sessions. Sessions were divided into four balanced half-hour epochs, half with visual feedback of true heart rate plus instructions to lower heart rate during approach to phobic stimulus. All patients improved significantly from the start to end of sessions on heart rate and on subjective anxiety. Feedback of heart rate plus instructions to lower it substantially reduced heart rate during epochs of feedback, compared to non-feedback epochs without instructions, but this effect did not generalize to skin conductance or to subjective anxiety in our short-term experiment.

Adult↗
PubMed1996

The effect of the amount of feedback on anxiety levels during ultrasound scanning.

This study examined the influence of different levels of feedback and of other situational and buffering variables on the psychological effects of ultrasound examinations of 211 pregnant women. The patients were randomly assigned to two different experimental conditions: high feedback and low feedback. The subjects' levels of anxiety (both trait- and state-anxiety) were measured immediately before and after the ultrasound examination. Overall, there was a significant decrease in the level of state-anxiety, which could not be explained by the different levels of feedback provided. Situational and buffering variables were not found to be related to the degree of psychological benefit produced by the scan.

Adult↗
PubMed1998

Using feedback on patient progress to predict the outcome of psychotherapy.

The Dose-Response and Phase Models are useful for informing quality assurance research on the expected patterns for separate categories of outcomes in psychotherapy. Moreover, these models predict the sequence of change for outcomes that may be differentially valued by patients, therapists, stakeholders, and cost managers. Valid feedback on the progress of treatment is critical because patients, therapists, and cost managers make decisions about continuation and focus of treatment while psychotherapy is in progress. In this study, the focus is on the validity of feedback data for therapist appraisal of patient progress. Feedback at patient intake, in early sessions of psychotherapy, and at later sessions of psychotherapy is considered. Among the variables examined are patient and therapist agreement on severity, level of severity, evidence of remoralization, and evidence of symptomatic remission. Data are drawn from archived records of 243 psychotherapy cases conducted in several managed care service delivery settings. The implications of a therapist's use of feedback to adjust the therapeutic process in an individual case are discussed.

Adult↗
PubMed2001

Controlling the immune system: diffuse feedback via a diffuse informational network.

Diffuse feedback is defined to be a process by which a system in some sense improves its performance with respect to a variety of conflicting and even contradictory goals. In the immune system, such feedback is mediated by scores of extracellular chemicals (cytokines), each of which participates in achieving several goals. Progress toward any given goal is mediated by several cytokines. The 'immunoinformatics' of this diffuse informational network will be discussed. It will be shown how diffuse feedbacks, based on this network, can improve the performance of a given type of immune effector cell, and can cause the preferential amplification of more potent effectors. It will be argued that diffuse feedback also acts in other biological systems ranging from the metabolic system to ant colonies.

Animals↗
PubMed2000

Fundamental GABAergic amacrine cell circuitries in the retina: nested feedback, concatenated inhibition, and axosomatic synapses.

Presynaptic gamma-aminobutyrate-immunoreactive (GABA+) profiles were mapped in the cyprinid retina with overlay microscopy: a fusion of electron and optical imaging affording high-contrast ultrastructural and immunocytochemical visualization. GABA+ synapses, deriving primarily from amacrine cells (ACs), compose 92% of conventional synapses and 98% of the input to bipolar cells (BCs) in the inner plexiform layer. GABA+ AC synapses, the sign-inverting elements of signal processing, are deployed in micronetworks and distinctive synaptic source/target topologies. Nested feedback micronetworks are formed by three types of links (BC --> AC, reciprocal BC <-- AC, and AC --> AC synapses) arranged as nested BC<--> [AC --> AC] loops. Circuits using nested feedback can possess better temporal performance than those using simple reciprocal feedback loops. Concatenated GABA+ micronetworks of AC --> AC and AC --> AC --> AC chains are common and must be key elements for lateral spatial, temporal, and spectral signal processing. Concatenated inhibitions may represent exceptionally stable, low-gain, sign-conserving devices for receptive field construction. Some chain elements are GABA immunonegative (GABA-) and are, thus, likely glycinergic synapses. GABA+ synaptic baskets target the somas of certain GABA+ and GABA- cells, resembling cortical axosomatic synapses. Finally, all myelinated intraretinal profiles are GABA+, suggesting that some efferent systems are sources of GABAergic inhibition in the cyprinid retina and may comprise all axosomatic synapses. These micronetworks are likely the fundamental elements for receptive field shaping in the inner plexiform layer, although few receptive field models incorporate them as functional components. Conversely, simple feedback and feedforward synapses may often be chimeras: the result of an incomplete view of synaptic topology.

Animals↗
PubMed1978

The effects of videotape feedback on self-concept, role-playing ability, and growth in a leaderless therapy group.

Thirty-two male and female college students participated in six 90-minute leaderless encounter groups in which they received videotape feedback, leader-facilitated videotape feedback, or verbal feedback. Statistical analysis indicated that feedback through a visual medium had no effect on self-concept, role-playing ability, or group coherence. Groups within the experimental conditions were initially different in their ratings on the dependent measures. These differences were maintained throughout the experiment.

Feedback↗
PubMed1980

Use of consumer feedback in planned change and evaluation activities.

Consumer feedback about services can be used to reward staff, stimulate improved performance, and make the service organization more responsive to consumer needs. Carefully collected consumer feedback can be used in a process of organizational planned change involving a cycle of problem perception and documentation, followed by the choice, implementation, and evaluation of solutions to these problems. Presently, consumer feedback is often poorly collected or inadequately utilized. Through preparation of concrete items related to manipulable aspects of service delivery, use of precoded response categories for items, and use of computers for data analysis, high quality consumer feedback can be obtained and used to pinpoint service delivery problems, evaluate solutions to problems, and evaluate the impact of other service changes and innovations.

Consumer Behavior↗
PubMed2006

Contribution of feedforward thalamic afferents and corticogeniculate feedback to the spatial summation area of macaque V1 and LGN.

Neurons in the primary visual cortex (V1) respond best to oriented gratings of optimal size within their receptive field (RF) and are suppressed by larger gratings involving the nonclassical RF surround. A V1 neuron's optimal stimulus size is larger at lower stimulus contrast. A central question in visual neuroscience is what circuits generate the size tuning of V1 cells. We recently demonstrated that V1 horizontal connections integrate signals within a region of the RF center corresponding to the V1 neuron's optimal stimulus size at low contrast; extrastriate feedback connections to V1, instead, are longer range and can integrate signals from the most distant regions of the V1 cell's RF surround. Here, we have determined the contribution of geniculocortical feedforward and corticogeniculate feedback connections to the size-tuning of macaque V1 and lateral geniculate (LGN) neurons, respectively. Specifically, we have quantitatively compared the visuotopic extent of geniculate feedforward afferents to V1 with the size of the RF center and surround of neurons in the V1 input layers and the visuotopic extent of V1 feedback connections to the LGN with the RF size of cells in V1 layer 6, where these connections originate. We find geniculate feedforward connections to provide visuotopic information to V1 that is spatially coextensive with the V1 neuron's optimal stimulus size measured with high-contrast gratings. V1 feedback connections restrict their influence to an LGN region visuotopically coextensive with the size of the minimum response field (or classical RF) of V1 layer 6 cells and commensurate with the LGN region from which they receive feedforward connections.

Animals↗
PubMed2007

Electrophysiological and hemodynamic evidence for late maturation of hand power grip and force control under visual feedback.

Several human imaging studies have described the neural network involved in power grip under visual control and the subset of cortical areas within this network that are sensitive to force modulation. As there is behavioral evidence for late maturation in even simple hand motor tasks involving visual feedback, we aimed at identifying the neural correlates of these developmental changes. Subjects from three developmental age groups (9-11, 15-17, and adults) performed the same power grip task in both a functional magnetic resonance imaging and an event-related potential (ERP) session. Trials started with a visual target indicating whether to squeeze at 20%, 40%, or 75% of their maximum and online visual feedback on the actual amount of force was provided. Longer reaction times and more shallow slopes of the force curve characterized the behavior of the younger age groups, especially the children. Both neurophysiological methods detected both general as well as force modulation-specific maturational changes. General development was characterized by decreasing ERP amplitudes and increasing deactivation of an extended network, closely resembling the so-called "default" network. The most pronounced developmental changes specific for force control were observed in an ERP component and brain regions involved in feedback processing. In contrast to adult subjects, we found evidence for a stronger dependency on visual feedback information in the younger age groups. Our results also suggest that the ability to deactivate task-irrelevant networks might be a late developmental achievement.

Adolescent↗
PubMed1991

Feedforward and feedback inhibition of hippocampal principal cell activity evoked by perforant path stimulation: GABA-mediated mechanisms that regulate excitability in vivo.

Hippocampal field potentials evoked by paired-pulse perforant path stimulation were used to identify normal feedforward and feedback inhibitory influences on hippocampal principal cells. Three distinct aspects of inhibitory function were identified in the dentate gyrus. They are: (1) first spike amplitude-dependent inhibition of the second spike, which at low stimulus frequency is primarily feedback in nature; (2) frequency-dependent inhibition of a single spike or the first spike of a pair, which occurs as stimulus frequency is increased from 0.1 to 1.0 Hz and which is primarily a reflection of feedforward inhibition; and (3) frequency-dependent inhibition of the second spike that is relatively independent of first spike amplitude and probably due to a combination of feedforward and feedback mechanisms. The results indicate that granule cell recurrent inhibition alone, evoked at low stimulus frequency, is relatively brief and weak. At higher frequencies, probably more relevant to physiological activity, feedforward inhibitory activity is recruited. The combination of feedforward and feedback mechanisms results in strong, maximal duration, granule cell inhibition. Similar frequency dependence of inhibition was not seen in area CA1 in response to ipsilateral perforant path stimulation since low frequency stimulation did not evoke CA1 spikes. CA3 stimulation did evoke large contralateral CA1 population spikes, but paired-pulse inhibition was weaker than that evoked by ipsilateral perforant path stimulation in terms of the duration of inhibition and the ability to suppress the development of epileptiform behavior. The identification of simple tests that reflect distinct inhibitory processes in vivo permits similar studies to be conducted in vitro to determine how to preserve inhibitory processes for cellular studies of normal and human epileptic tissue in which the state of excitatory--inhibitory balance is the subject. These results also form the basis for the interpretation of the following study (Sloviter, 1991), which addresses the relationship between selective dentate interneuron loss and the pathophysiology that accompanies it.

Animals↗
PubMed2003

Mutation analysis of the feedback inhibition site of phenylalanine-sensitive 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase of Escherichia coli.

In Escherichia coli, the phenylalanine-sensitive 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHPS) AroG catalyzes the first committed step in the biosynthesis of aromatic compounds. To investigate the feedback inhibition site of AroG, mutated enzymes prepared with sequence-overlap extension PCR were expressed and purified. The enzymatic activity assay showed that the amino acid replacements at Phe144, Leu175, Leu179, Phe209, Trp215Ala and Val221 completely or partially relieved feedback inhibition of AroG addressed by the phenylalanine. Ile10Ala and Delta(1-15) desensitized feedback inhibition and caused a 70 approximately 90% loss of the specific catalytic activities. These results strongly suggest an involvement of the interior region and the N-terminus of the polypeptide chain of AroG in the formation of the feedback inhibition site of DAHPS.

3-Deoxy-7-Phosphoheptulonate Synthase↗
PubMed2006

Movement-based feedback may reduce spinal moments in male workers during lift and lowering tasks.

BACKGROUND AND PURPOSE: To assess if lifting performance can be modified and spine stresses reduced in workers who perform repetitive material-handling jobs in a warehouse environment via a novel real-time, movement-based feedback training protocol. METHOD: A pre-test/post-test group study design was used with a control group. Data were collected in a warehouse setting and analysed in a university setting. A convenience sample of 22 male warehouse employees was divided equally, based on height and weight, and assigned to either an experimental group or a control group. The experimental group received real-time, performance-based auditory feedback from their calculated moments during lifting or lowering using an electromagnetic tracking system. The electromagnetic tracking system was used to measure the side-bending, flexion and rotation moments during six lifts under four different conditions. A series of repeated-measures analyses of variance (ANOVA) (one between (Group); one within (Time)) was performed on the average maximum moments from six lifting or lowering cycles for all three directions: side-bending, flexion and rotation. RESULTS: There were significant group x time interactions for the side-bending moment (p < 0.05) and the flexion moment (p < 0.05) but not the rotation moment (p > 0.05). Lower moments were found in the experimental group, which received the training and feedback, compared to the control group. CONCLUSIONS: Real-time, auditory feedback combined with coaching during lifting or lowering tasks may be effective in the short term (six weeks) in reducing the average maximum side-bending and flexion moments in warehouse workers. Further research is needed to determine the long-term effects of this training protocol on low back injury rates.

Analysis of Variance↗