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Results for “Video feedback”

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At least 343 records · Page 19Linked to original sources

PubMed1996

[Minimally invasive ENT surgery. Progress due to modern technology].

Three fundamentals have to be fulfilled to optimize minimally, invasive surgery: three-dimensional imaging, free maneuverability of the instruments, sensorial feedback. Projection of two pictures from a stereoendoscope and subsequent separation with a LCD shutter allows three-dimensional videoendoscopy to be performed. A high-frequency shutter technique (100/120 Hz) presents pictures from the two video cameras to the right and left eye, respectively, so that the surgeon has spatial vision of the operative field. Steerable instruments have four component: a control unit, rigid shaft, steerable multi-joints, distal effector. The steerable multi-joints give two additional degrees of freedom compared to conventional rigid instruments in endoscopic surgery. For intuitive movements, however, an electronic control system is necessary that is comparable to the "master-slave" principle in remote technology. A remote manipulator system with six degrees of freedom is now available. Additionally, a multifunctional distal tip permits different surgical steps to be performed without changing the instrument. For better control of the instrument and the operative procedure tactile feedback can be achieved with appropriate microsensor systems. Recent projects suggest that an artificial sensor system can be established within the foreseeable future.

Endoscopes↗

PubMed2003

The effect of gravity on the stability of human eye orientation.

OBJECTIVE: The stabilization of both the horizontal (H) and vertical (V) eye movements during voluntary fixation is believed to depend upon the visual feedback system in the upright position. However, ocular stability in the tilted position has been less well investigated. Therefore, in the present study, we examined the gaze stability of healthy human subjects in the three dimensions in the tilted position using a video image analysis system (VIAS). METHODS: In 10 healthy human subjects, the eye movements were recorded after fixating the eye on a target in an upright position and also in the tilted position. The standard deviations of the eye movements in the three dimensions were calculated to evaluate the stability of the movements. RESULTS: In the tilted position, there were no significant changes in the horizontal and vertical eye movements as compared those in the upright position. However, the standard deviation of the torsional (T) segment was significantly larger in the tilted position, compared to that in the upright position. CONCLUSION: From these results, we speculate that, a combination of otolith and somatosensory inputs play a major role in maintaining the stability of eye movements.

Adult↗

PubMed2005

Improving the accuracy and reliability of motion tracking methods used for extracting temporal motor activity signals from video recordings of neonatal seizures.

This paper presents an approach for improving the accuracy and reliability of motion tracking methods developed for video based on block motion models. This approach estimates the displacement of a block of pixels between two successive frames by minimizing an error function defined in terms of the pixel intensities at these frames. The minimization problem is made analytically tractable by approximating the error function using a second-order Taylor expansion. The improved reliability of the proposed method is illustrated by its application in the extraction of temporal motor activity signals from video recordings of neonatal seizures.

Algorithms↗

PubMed2004

Functional evaluation of natural sensory feedback incorporated in a hand grasp neuroprosthesis.

We investigated whether automatic control of a hand grasp neuroprosthesis by means of signals from natural sensors in the skin of the index finger can mimic the natural control of grasp force in an important task of daily living, namely eating. We designed a simulated eating task with the same ratio of rest and activity as was found on average in a video analysis of three meals consumed in a social environment. An instrumented fork measured grasp force as well as the force in the long axis and perpendicular to the long axis at the tip of the fork. The simulated eating task was performed by a tetraplegic volunteer using a hand grasp neuroprosthesis both with and without use of feedback from the natural sensors. Further, 10 able-bodied volunteers performed the task with the same (lateral) grasp as the tetraplegic volunteer to obtain measures for improving the control strategy of the hand grasp neuroprosthesis. We have shown that a hand grasp neuroprosthesis incorporating natural sensory feedback can to some extent mimic the natural application of grasp force on a fork during simulated eating. The mean grasp force during active phases was higher than the mean grasp force during inactive phases. The mean grasp force applied during a simulated eating task was reduced by using the system with sensory feedback compared to using the system without sensory feedback.

Activities of Daily Living↗

PubMed1997

Minimal invasive ear, nose and throat surgery--advances through modern technologies.

Three fundamentals have to be fulfilled to optimize minimally invasive surgery: three-dimensional imaging, free maneuverability of the instruments, sensorial feedback. Projection of two pictures from a stereoendoscope and subsequent separation with a LCD shutter allows three-dimensional videoendoscopy to be performed. A high frequency shutter technique (100/120 Hz) presents pictures from the two video cameras to the right and left eye, respectively, so that the surgeon has spatial vision of the operative field. Steerable instruments have four components: a control unit, rigid shaft, steerable multijoint, distal effector. The steerable multijoints give two additional degrees of freedom compared to conventional rigid instruments in endoscopic surgery. For intuitive movements, however, an electronic control system is necessary that is comparable to the "master slave" priniciple in remote technology. A remote manipulator system with six degrees of freedom is now available. Additionally, a multifunctional distal tip permits different surgical steps to be performed without changing the instrument. For better control of the instrument and the operative procedure tactile feedback can be achieved with appropriate microsensor system. Recent projects suggest that an artificial sensor system can be established within the foreseeable future.

Ear↗

PubMed2001

The stability of human eye orientation during visual fixation and imagined fixation in three dimensions.

OBJECTIVE: The stabilization of eye movements during voluntary fixation is believed to depend upon the visual feed back, since gaze becomes less stable in the darkness. The temporal variability of human eye orientation in both the horizontal and vertical direction is typically no more than a few minutes of arc. Ocular stability in terms of torsion has, however, been less understood. METHODS: In this study, the stability of gaze in the three dimensions (horizontal, vertical, and torsional) was investigated using a video image analysis system. In ten healthy subjects, eye movements were recorded after fixating the eye on a target in the light and also in the dark (imaginary target). The standard deviations of the eye movements in the three dimensions were calculated during fixation. RESULTS: In the light, the horizontal and vertical eye movements exhibited an alternating sequence of a slow drift and resetting microsaccades, as previously reported. The torsional eye movements, however, showed no such drifts and resetting. In the dark, the horizontal and vertical eye movements exhibited about 2-3 times larger value of the standard deviation than that in the light. In contrast to this, the difference in the standard deviation between the light and dark was not so prominent in case of the torsional eye movement as compared to those of horizontal and vertical. CONCLUSION: These results support the idea that information from the peripheral retina does not significantly influence the feed back system for fixating the target in the light.

Adult↗

PubMed1991

EMG biofeedback treatment of torticollis: a controlled outcome study.

Successful treatment of torticollis with electromyographic (EMG) biofeedback has been reported in a number of single case and single group studies. The present investigation represents the first controlled outcome study. Twelve torticollis patients were randomly assigned to EMG biofeedback or relaxation training and graded neck exercises (RGP). The procedure involved three sessions of baseline assessment, 15 sessions of EMG BF or RGP, 6 sessions of EMG BF or RGP plus home-management, 6 sessions of home-management alone, and follow-up 3 months after the end of treatment. A variety of outcome measures were used including physiological (EMG from the two sternocleidomastoid muscles, skin conductance level), behavioral (angle of head deviation, range of movement of the head), and self-report (depression, functional disability, body concept), therapist and "significant other" reports and independent observer assessment of videos. In both groups, neck muscle activity was reduced from pre- to posttreatment. This reduction was greater in the EMG biofeedback group. There was evidence of feedback-specific neck muscle relaxation in the EMG biofeedback group. Therefore, the outcome was not due to nonspecific factors and could be attributed to feedback-specific effects. Changes in skin conductance level showed that neck muscle relaxation was not simply mediated by a general reduction of "arousal." Significant improvements of extent of head deviation, and range of movement of the head, as well as reductions of depression were present, which were not different in the two groups. At the end of treatment, no patient was asymptomatic. Any therapeutic benefit was generally maintained at follow-up. The results and the procedural simplicity of RGP make the issue of cost-efficacy of EMG biofeedback a pertinent one. Further controlled outcome studies of EMG biofeedback treatment of torticollis with larger samples are required.

Adult↗

PubMed1994

The use of videotape in internal medicine training.

By paying attention to the power of the medium and the method of feedback, videotaping programs can be a remarkably successful teaching and research tool. Learners can view their performance, review feedback on their own behavior, knowledge, and displayed attitudes, and develop plans to change behavior that can be followed up on subsequent tappings. In addition, trainees can share important experiences with each other and valued teachers. Interviewing skills can be documented and preserved, creating a video library that allows trainees to actually visualize improvements in their own performances over time. An archive of many such performances allows trainees, faculty, and researchers alike comparative access to the complex challenges of the medical interview.

Decision Making↗

PubMed1993

Self-awareness, task failure, and disinhibition: how attentional focus affects eating.

Dieting and nondieting subjects were given either failure or neutral performance feedback on a problem-solving task. Failure subjects were then assigned to one of three self-awareness conditions: One group was forced to watch a video clip of themselves failing on the problem-solving task, one group was asked to watch a distracting video clip on bighorn sheep, and the final group was asked to sit quietly for 10 minutes. Subjects were then allowed to eat as much ice cream as they wanted. Only in those conditions which allowed--or promoted--low self-awareness (the failure/distraction and simple failure condition) did dieters show disinhibited eating. In the failure/videotape condition, which enforced high levels of self-awareness, eating in dieters remained inhibited. This supports the proposal that a reduction in self-awareness is necessary for lifting of inhibitions. Eating in nondieters was reduced in the failure/videotape and simple failure conditions, possibly because of the autonomic correlates of distress.

Achievement↗

PubMed1997

Video sequence compression via supervised training on cellular neural networks.

In this paper, a novel approach for video sequence compression using Cellular Neural Networks (CNN's) is presented. CNN's are nets characterized by local interconnections between neurons (usually called cells), and can be modeled as dynamical systems. From among many different types, a CNN model operating in discrete-time (DT-CNN) has been chosen, its parameters being defined so that they are shared among all the cells in the network. The compression process proposed in this work is based on the possibility of replicating a given video sequence as a trajectory generated by the DT-CNN. In order for the CNN to follow a prescribed trajectory, a supervised training algorithm is implemented. Compression is achieved due to the fact that all the information contained in the sequence can be stored into a small number of parameters and initial conditions once training is stopped. Different improvements upon the basic formulation are analyzed and issues such as feasibility and complexity of the compression problem are also addressed. Finally, some examples with real video sequences illustrate the applicability of the method.

Algorithms↗

PubMed2005

[Trends of electronic publishing in medicine and life sciences].

Scientific publication in the electronic media is gaining popularity in academic libraries, research institutions and commercial organizations. The electronic journal may shorten the processes of writing and publication, decrease publication and distribution costs, and enable access from any location in the world. Electronic publications have unique advantages: it is possible to search them, to create hyperlinks to references and footnotes, as well as to information on the web and to include graphics and photographs at a very low cost. Audio, video and tri-dimensional images may also be included. Electronic publishing may also speed up review and publication processes and enable the writer to receive immediate feedback through the web. However, in spite of the advantages, there are certain points that must be considered: accessibility to previously published material is not guaranteed as databases are not always stable and coverage may change without notice. In addition, the price that commercial publishers charge for their services may be very high or be subject to the purchase of a packaged deal that may include unwanted databases. Many issues of copyright and the use of published material are not yet finalized. In this review we discuss the advantages and disadvantages of the electronic scientific publication, the feasibility of keeping appropriate quality and peer-review process, the stability and accessibility of databases managed by the publishers and the acceptance of the electronic format by scientists and clinicians.

Biological Science Disciplines↗

PubMed2006

Video coding with fixed-length packetization for a tandem channel.

A robust scheme is presented for the efficient transmission of packet video over a tandem wireless Internet channel. This channel is assumed to have bit errors (due to noise and fading on the wireless portion of the channel) and packet erasures (due to congestion on the wired portion). First, we propose an algorithm to optimally switch between intracoding and intercoding for a video coder that operates on a packet-switched network with fixed-length packets. Different re-synchronization schemes are considered and compared. This optimal mode selection algorithm is integrated with an efficient channel encoder, a cyclic redundancy check outer coder concatenated with an inner rate-compatible punctured convolutional coder. The system performance is both analyzed and simulated. Last, the framework is extended to operate on a time-varying wireless Internet channel with feedback information from the receiver. Both instantaneous feedback and delayed feedback are evaluated, and an improved method of refined distortion estimation for encoding is presented and simulated for the case of delayed feedback.

Algorithms↗

PubMedDate not supplied

Combined intracellular stimulation and high speed video motion analysis of motor control neurons in the cockroach.

A complete understanding of motor control circuitry requires detailed analysis of the behavior produced by the circuitry as well as the connections between individual neurons. A technique is described for combining high speed video motion analysis of leg movements in the cockroach with electrophysiological techniques such as intracellular stimulation/recording from central neurons and EMG recording from leg muscles. Using a restrained preparation, we have quantified leg movements evoked by intracellular stimulation of individual motor neurons and local interneurons. By incorporating motion analysis into the recording paradigm, the transfer functions from electrical activity to movements can be derived. Because distinct and characteristic responses to single and multiple action potentials are seen in slow, intermediate, and fast motor neurons, it is often possible to identify the motor neuron targets of local interneurons. The ability to analyze movement in any plane is especially useful in situations such as blind neuropilar penetrations, where a more restricted motion transducer arrangement may not be in register with the impaled cell. In addition, it is possible to record and analyze such complex phenomena as coordinated movements in multiple joints produced by local interneurons and reflexes produced by proprioceptive feedback due to activity of one motor neuron.

Animals↗

PubMed1996

Force feedback for virtual reality based minimally invasive surgery simulator.

This paper presents ongoing research towards an endoscopic surgery simulation system. Our specific application of interest is laparoscopic surgery. The goal is to conceive an endoscopic surgical training tool which allows to realistically simulate the interactions between one or several surgical instruments and the gastrointestinal organs in a virtual reality based environment. An artificial patient is being developed into which endoscopic surgical instruments can be inserted to operate upon virtual organs displayed on a video monitor. In order to achieve a faithful and precise simulation, not only a realistic graphical representation of the organic tissue and its behavior is needed, but also the forces and moments on the surgical instruments encountered during an operation are required to be simulated. The laparoscopic surgery simulator must therefore provide force feedback through the endoscopic instruments manipulated by the surgeon. This paper details the mechanical design of the force feedback mechanisms and addresses some of the technical challenges of this project.

Computer Simulation↗

PubMed1993

Computer-aided vascular experimentation: a new electromechanical test system.

We present a new computer-controlled, electromechanical system for performing simultaneous extension, inflation, and torsion experiments on cylindrical segments of natural and artificial blood vessels. Specimens are tested while immersed in a temperature-controlled, oxygenated, physiologic solution. Deformations are measured within a central region of the specimen using noncontacting video methods. The associated axial loads, luminal pressures, and torques are measured with standard transducers. Data are collected and stored on-line, and are used in the feedback control of experimental protocols, which are prescribed using custom interactive software. Finally, we present illustrative data obtained from canine aortas and common carotid arteries.

Animals↗

PubMed1993

Physiological deactivation after two contrasting tasks at a video display terminal: learning vs repetitive data entry .

Two contrasting 90 min VDT work situations were simulated in the laboratory: (1) a machine-paced, repetitive data entry task; and (2) a stimulating, self-paced learning task with successive feedback. Thirty non-smoking male students (20-34 years), without previous experience of VDT work, participated individually in each condition on two consecutive days (balanced order) and in a task-free baseline condition. Self-reports and successive measurements (ambulatory recordings) of systolic and diastolic blood pressure and heart rate were obtained during work and during a subsequent 60 min period of deactivation. Urine samples were obtained after each period for the determination of catecholamines and cortisol. In the baseline condition, measurements were obtained at corresponding times of the day. As expected, the data entry task was associated with self-reports of boredom, irritation, and unpleasantness; the learning task wtih alertness, interest, and ability to concentrate. Similar elevations of physiological measurements occurred in both work situations. However, differences between conditions were found after work. Following data entry, deactivation was slower in five of the six variables (significant for epinephrine).

Adult↗

PubMed2001

Prism adaptation of reaching is dependent on the type of visual feedback of hand and target position.

The present study demonstrated that the magnitude of after-effect due to wedge prisms depends on the form of the visual feedback used to represent hand and target position in fast, targeted, transverse reaches. Trained human subjects made reaches with and without prisms in three visuomotor representations (VR): (1) the subject's actual hand and targets (Direct), (2) a real-time video broadcast of hand and targets (Video), or (3) abstract, computer-generated targets and a cursor representing hand position (Cursor). A significant after-effect occurred in each VR. However, the magnitude of the after-effect was significantly different among VRs: the magnitude was greatest in Direct, smaller in Video and smallest in Cursor. A significant after-effect (carryover) also occurred when a subject prism-adapted reaches in one VR and then removed the prisms and made initial reaches in another VR. Our data showed that when reaches were prism-adapted in Direct and then prisms were removed, there was a large carryover to initial reaches in Video or Cursor (D-->V and D-->C). In contrast, when prisms were worn in Video and removed for reaches in Direct (V-->D), there was a significantly smaller carryover than from both D-->V and D-->C. Finally, when prisms were worn in Cursor and removed for reaches in Direct (C-->D), there was very little detectable carryover. Our results suggest that adaptation is context-dependent and that the magnitude of carryover is dependent on the VR in which adaptation occurred. Interpretations of adaptations made in abstract training and experimental conditions may be greatly affected by this finding.

Adaptation, Physiological↗

PubMed2003

Effects of haptic feedback and turbulence on landing performance using an immersive cave automatic virtual environment (CAVE).

An investigation was conducted in which subjects had to land a simulated F-16 aircraft using a CAVE (Cave Automatic Virtual Environment) facility. This was a three-dimensional virtual setting consisting of multiple mirrors, 3-D video-projected displays in a highly stressful environment employing a haptic joystick. 6 subjects learned a task which required landing in wind turbulence with a reduced visual scene. Analyses indicated that during landing, performance error variables which occurred in the same direction as the haptic forces were significantly reduced. This was true, especially when the visual scene was occluded and more reliance on the proprioceptive condition was beneficial.

Adult↗