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PubMedDate not supplied

Biofeedback as a treatment for postural hypotension.

Two patients with cervical spinal cord lesions were treated for postural hypotension using auditory and visual feedback for voluntary increases in blood pressure. Following initial measures of blood pressure, feedback was delivered for systolic increases above baseline. Within several weeks, both patients learned to increase their pressure markedly from the start of training sessions to their conclusion. The patients' legs were progressively lowered during and at the end of training sessions without significant blood pressure decreases. Long-term follow-up indicated that they were able to maintain the learned increases in blood pressure despite adverse medical conditions. It is suggested that central nervous system damage disrupts homeostatic regulation, permitting greater voluntary control through biofeedback as a new feedback loop. Motivation is also considered an important variable for success.

Adult↗

PubMed1998

The measurement of lumbar proprioception in individuals with and without low back pain.

STUDY DESIGN: A clinical trial comparing a back pain group with a pain-free group. OBJECTIVES: To investigate whether proprioceptive deficits existed in a group of individuals reporting low back pain. SUMMARY OF BACKGROUND DATA: Little work has so far been conducted on the measurement of proprioception in the spine. Those studies that have been carried out, however, have failed to identify proprioceptive deficits in individuals with back pain. Previous work on peripheral joints has revealed that proprioception is affected with muscular or joint injury or degeneration. METHODS: Forty individuals took part in the study, 20 with back pain and 20 with no pain. Participants were required to reproduce a predetermined target position, in standing and four-point kneeling, 10 times in 30 seconds. A computer screen was used to provide visual feedback on position. A mean deviation from the target position was obtained for each individual. A measurement of left elbow position sense was conducted in five individuals from each group to establish differences in short-term motor memory between the groups. RESULTS: There were no differences between the subject groups in terms of short-term motor memory (P > 0.05). A two-way analysis of variance between subject groups and position to identify differences in accuracy (deviation from the target) found that there were differences between subject groups in either position (P < 0.05). There was no significant difference in accuracy between the positions used (P > 0.05). CONCLUSIONS: Differences in proprioception do exist between individuals with back pain and those free from back pain. Further research needs to be undertaken on proprioceptive exercise programs and their effect on back pain.

Adult↗

PubMed1994

Ocular movements.

The internal representation of saccade commands has been shown to combine with visual information for saccade programming. In normative studies saccade parameters have been found consistent across tests. Their variability is highly correlated in both eyes suggesting a common saccade generator. Experimental and clinical studies specify the role of frontal eye fields in the volitional, inhibitory control of visually triggered saccades. The parietal lobe instead seems mainly concerned with privileged target selection. A parallel processing of saccade related signals occurs in corticostriatal circuits. Pursuit movements elicited by intermittently illuminated moving targets result from a predictive estimate of eye velocity based on previous eye velocity and visual feedback. Evidence for peristriate and parietal cortical areas to encode the information relevant to smooth pursuit generation is provided by clinical studies.

Brain Stem↗

PubMed2003

Reposition sense of lumbar curvature with flexed and asymmetric lifting postures.

STUDY DESIGN: Reposition sense of lumbar curvature was assessed as a function of trunk flexion, trunk asymmetry, and target lumbar curvature using a repeated-measures design and an active-active proprioception paradigm. OBJECTIVE: The objectives of the research were to measure the ability of the subjects to sense and control the lumbar curvature in different lifting postures and to see if error in the lumbar curvature would increase in high-risk postures. SUMMARY OF BACKGROUND DATA: The risk of low back disorders (LBDs) is related to trunk posture, with greater risk reported in flexed and asymmetric trunk positions. Spinal posture, including trunk position and lumbar lordosis, influences spinal stability. Hence, the ability to accurately sense and control spinal curvature may be an important factor in the control of LBD risk. METHODS: Eleven subjects were trained to assume specified lumbar curvatures using visual feedback. The ability of the subjects to reproduce this curvature without feedback was then assessed. This procedure was repeated for different trunk postures, including flexion and asymmetry, and with different target lumbar curvatures. RESULTS: These measurements demonstrated reposition error was increased in flexed trunk positions but was unchanged with trunk asymmetry. This increase in reposition error with flexion was diminished when the target posture and lumbar curvature were highly flexed and kyphotic. CONCLUSIONS: This research suggests that it may be difficult to control spinal curvature in flexed positions, leading to an increased risk of injury. For jobs in which flexed working postures are unavoidable, therefore, it is important to minimize potentially unstable events such as slipping or shifting loads to avoid injury.

Adult↗

PubMed2005

Three-dimensional rotational X-ray imaging for spine surgery: a quantitative validation study comparing reconstructed images with corresponding anatomical sections.

STUDY DESIGN: A validation study was done in which reconstructed three-dimensional rotational x-ray images were quantitatively compared with corresponding anatomic sections. OBJECTIVES: To assess the accuracy of reconstructed images acquired on a three-dimensional rotational x-ray imaging device. SUMMARY OF BACKGROUND DATA: Minimally invasive procedures have proven quite successful as alternatives for a multitude of open treatments. An unfavorable property of this type of procedure is a lack of direct vision of the operating area. Three-dimensional rotational x-ray imaging may be able to merge the advantages of computed tomography and fluoroscopy: real-time two-dimensional projections for fast visual feedback and three-dimensional reconstructions for detailed volumetric imaging of complex anatomy. METHODS: Twenty traumatic thoracolumbar burst fractures were created and underwent pedicle screw instrumentation and balloon vertebroplasty. Subsequently, a three-dimensional dataset was obtained, and the midsagittal image was reconstructed. The specimens were sliced, and photographs were obtained. Multiple parameters on the reconstructed images and photographs were measured two times by two observers using a graphical method. The differences and standard deviations were calculated for the corresponding parameters and for the intraobserver data. RESULTS: The mean difference between the corresponding values ranged between -1.1 and 2.1 mm for all parameters. The standard deviation for the differences per parameter ranged between 1.2 and 3.2 mm. The intraobserver differences ranged from -0.8 to 1.4 mm, and the standard deviation varied between 0.4 and 2.4 mm. CONCLUSIONS: The reconstructed midsagittal images were accurate in all measured parameters. The three-dimensional rotational x-ray technique may prove to be valuable for less invasive spine surgery.

Aged↗

PubMed2004

Short-term effects of whole-body vibration on postural control in unilateral chronic stroke patients: preliminary evidence.

The short-term effects of whole-body vibration as a novel method of somatosensory stimulation on postural control were investigated in 23 chronic stroke patients. While standing on a commercial platform, patients received 30-Hz oscillations at 3 mm of amplitude in the frontal plane. Balance was assessed four times at 45-min intervals with a dual-plate force platform, while quietly standing with the eyes opened and closed and while performing a voluntary weight-shifting task with visual feedback of center-of-pressure movements. Between the second and third assessments, four repetitions of 45-sec whole-body vibrations were given. The results indicated a stable baseline performance from the first to the second assessment for all tasks. After the whole-body vibration, the third assessment demonstrated a reduction in the root mean square (RMS) center-of-pressure velocity in the anteroposterior direction when standing with the eyes closed (P < 0.01), which persisted during the fourth assessment. Furthermore, patients showed an increase in their weight-shifting speed at the third balance assessment (P < 0.05) while their precision remained constant. No adverse effects of whole-body vibration were observed. It is concluded that whole-body vibration may be a promising candidate to improve proprioceptive control of posture in stroke patients.

Chronic Disease↗

PubMed2005

Injections in patients with osteoarthritis and other musculoskeletal disorders: use of synthetic injection models for teaching physiatry residents.

This study examined whether resident injection skills could be enhanced using synthetic injection models. A total of 30 physiatry residents underwent written and injection-model pretesting and posttesting. After randomization into injection-model and control groups, the experimental group trained by watching an instructional videotape and by using models that gave visual feedback on injection accuracy, whereas the control group studied technical aspects of injections. Immediately after patient injections, a blinded attending graded residents on the required level of verbal or manual assistance. The experimental group performed significantly better during patient injections as per first injection data (i.e., the scores obtained from performing a procedure for the first time on each particular body region; P = 0.013), total injection data (i.e., the mean scores obtained from performing all procedures on each particular body region; P = 0.017), and postrotation practical testing (P < 0.007) but not for didactic knowledge (postrotation written testing; P < 0.039). Data analysis by body region showed significant benefit only for occasionally performed patient injection procedures. The benefit was most evident in less experienced residents. Injection-model accuracy testing correlated with actual patient injections, both for first injections into each major body region (r = 0.52, P = 0.005) and for all injections (r = 0.55, P = 0.003). Consideration should be given for incorporating injection-model training into residency education, especially for residents with less injection experience and for occasionally performed procedures. The overall correlation between model practical testing and subsequent patient injection performance suggests that models can measure injection competence.

Clinical Competence↗

PubMedDate not supplied

Behavioral analysis of Drosophila landmark learning in the flight simulator.

Drosophila flies can be trained in the flight simulator to operantly avoid heat by choosing certain orientations relative to landmarks. Flies primarily store pattern orientations associated with the absence of heat. They readily escape from heat-associated orientations under the direct influence of the reinforcer but not in the subsequent memory tests. The flies tend to keep the largest possible distance from the "hot" or potentially "hot" regions, that is, they head toward the center of the "cold" sector. The results are discussed in the light of the retinotopic matching model explaining visual memory in flies by the superposition of a retinotopically stored template with the actual retinal image. Window experiments confining visual feedback to two 90 degrees sectors indicate that the memory template covers most of the visible space.

Animals↗

PubMedDate not supplied

Evidence for processing stages in skill acquisition: a dual-task study.

We investigated the changes of resource demand during the acquisition of a sensorimotor skill, namely the tracking of a visual target under reversed visual feedback. This acquisition task was performed alone or concurrently with one of four manual reaction-time tasks as loading tasks, designed to tap different computational resources. As expected, we found tracking performance to deteriorate upon vision reversal and then to gradually improve with practice. We further found that acquisition task and loading task interfered little before vision reversal but substantially afterwards. Most importantly, we observed a different time-course of interference for each of our four loading tasks. The particular pattern led us to conclude that resources related to spatial attention and sensory transformations are in highest demand early during skill acquisition and those pertinent to movement preparation somewhat later. Our findings thus provide experimental support for the theory that motor learning progresses in stages characterized by different resource requirements.

Adult↗

PubMedDate not supplied

Learning motor synergies makes use of information on muscular load.

Prism adaptation, a form of procedural learning, requires the integration of visual and motor information for its proper acquisition. Although the role of the visual feedback has begun to be understood, the nature of the motor information necessary for the development of the adaptation remains unknown. In this work we have tested the idea that modifying the arm load at different stages of the adaptation process, and the ensuing change of motor information perceived by the subjects, would modify the final properties of the adaptation. We trained a set of subjects to throw balls to a target while wearing prism glasses and varied the weight of their arms at different time points during the task. We observed that the acquisition of the adaptation was not affected by the change in load. However, its persistence (i.e., the aftereffect) was reduced when tested under a weight condition different from the training trials. Furthermore, when the training weight conditions were restored later during testing, a second, late aftereffect was unmasked, suggesting that the missing aftereffect did not disappear but had remained latent. Our results show that the internal representation of a motor memory incorporates information about load conditions and that the memory stored under a specific weight condition can be fully retrieved only when the original training condition is restored.

Adolescent↗

PubMed1998

Initial component control in disparity vergence: a model-based study.

The dual-mode theory for the control of disparity-vergence eye movements states that two components control the response to a step change in disparity. The initial component uses a motor preprogram to drive the eyes to an approximate final position. This initial component is followed by activation of a late component operating under visual feedback control that reduces residual disparity to within fusional limits. A quantitative model based on a pulse-step controller, similar to that postulated for saccadic eye movements, has been developed to represent the initial component. This model, an adaptation of one developed by Zee et al. [1], provides accurate simulations of isolated initial component movements and is compatible with the known underlying neurophysiology and existing neurophysiological data. The model has been employed to investigate the difference in dynamics between convergent and divergent movements. Results indicate that the pulse-control component active in convergence is reduced or absent from the control signals of divergence movements. This suggests somewhat different control structures of convergence versus divergence, and is consistent with other directional asymmetries seen in horizontal vergence.

Adult↗

PubMed1998

An ultrasonic approach to localization of fiducial markers for interactive, image-guided neurosurgery--Part I: Principles.

Fiducial markers are reference points used in the registration of image space(s) with physical (patient) space. As applied to interactive, image-guided surgery, the registration of image space with physical space allows the current location of a surgical tool to be indicated on a computer display of patient-specific preoperative images. This intrasurgical guidance information is particularly valuable in surgery within the brain, where visual feedback is limited. The accuracy of the mapping between physical and image space depends upon the accuracy with which the fiducial markers were located in each coordinate system. To effect accurate space registration for interactive, image-guided neurosurgery, the use of permanent fiducial markers implanted into the surface of the skull is proposed in this paper. These small cylindrical markers are composed of materials that make them visible in the image sets. The challenge lies in locating the subcutaneous markers in physical space. This paper presents an ultrasonic technique for transcutaneously detecting the location of these markers. The technique incorporates an algorithm based on detection of characteristic properties of the reflected A-mode ultrasonic waveform. The results demonstrate that ultrasound is an appropriate technique for accurate transcutaneous marker localization. The companion paper to this article describes an automatic, enhanced implementation of the marker-localization theory described in this article.

Adipose Tissue↗

PubMed2001

A pilot study of myoelectrically controlled FES of upper extremity.

Functional electrical stimulation (FES) of upper limbs can be used for the recovery of some hand functions on patients with CNS lesions. This study deals with the control of FES by means of myoelectrical activity detected from voluntarily activated paretic muscles. The specific aim of this paper is to evaluate the accuracy of myoelectrical control in terms of produced force and movement. For this purpose, a specific device called myoelectrical controlled functional electrical stimulator (MeCFES) has been developed and applied to six tetraplegic patients with a spinal cord lesion and one stroke hemiplegic patient. Residual myoelectric signals from the paretic wrist extensor (m. extensor carpi radialis, ECR) have been used to control stimulation of either the wrist extension (i.e., the same muscle) or thumb flexion. A tracking test based on a visual feedback of the produced force or movement compared to a reference target trajectory was used to quantify control accuracy. A comparison was made between the tracking performances of each subject with and without the MeCFES and the learning process for two of the subjects were observed during consecutive sessions. Results showed that the wrist extension was improved in three out of five C5 SCI patients and the thumb flexion was largely increased in one incomplete C3 SCI patient. The hemiplegic patient showed limited thumb control with the MeCFES but indicated the possibility of a carry over effect. It was found that a low residual natural force resulted in a less accurate movement but also with a large increase (up to ten times) of the muscle output. On the contrary, persons with a medium residual force obtained a smaller amplification of muscle force with a higher tracking accuracy.

Adult↗

PubMed1998

Performance statistics of a head-operated force-reflecting rehabilitation robot system.

Researchers in the rehabilitation engineering community have been designing and developing a variety of passive/active devices to help persons with limited upper extremity function to perform essential daily manipulations. Devices range from low-end tools such as head/mouth sticks to sophisticated robots using vision and speech input. While almost all of the high-end equipment developed to date relies on visual feedback alone to guide the user providing no tactile or proprioceptive cues, the "low-tech" head/mouth sticks deliver better "feel," because of the inherent force feedback through physical contact with the user's body. However, the disadvantage of a conventional head/mouth stick is that it can only function in a limited workspace and the performance is limited by the user's strength. It therefore seems reasonable to attempt to develop a system that exploits the advantages of the two approaches: the power and flexibility of robotic systems with the sensory feedback of a headstick. The system presented in this paper reflects the design philosophy stated above. This system contains a pair of master-slave robots with the master being operated by the user's head and the slave acting as a telestick. Described in this paper are the design, control strategies, implementation and performance evaluation of the head-controlled force-reflecting telestick system.

Adult↗

PubMed2000

Controlling mouse pointer position using an infrared head-operated joystick.

This paper describes the motivation for and the design considerations of a low-cost head-operated joystick. The paper briefly summarizes the requirements of head-operated mouse pointer control for people with disabilities before discussing a set of technological approaches that can be used to satisfy these requirements. The paper focuses on the design of a head-operated joystick that uses infrared light emitting diodes (LED's) and photodetectors to determine head position, which is subsequently converted into signals that emulate a Microsoft mouse. There are two significant findings. The first is that, while nonideal device characteristics might appear to make the joystick difficult to use, users naturally compensate for nonlinearities, in a transparent manner, because of visual feedback of mouse pointer position. The second finding, from relatively informal, independent trials, indicates that disabled users prefer a head-operated device that has the characteristics of a joystick (a relative pointing device) to those of a mouse (an absolute pointing device).

Attitude to Health↗

PubMed2004

Robot-assisted adaptive training: custom force fields for teaching movement patterns.

Based on recent studies of neuro-adaptive control, we tested a new iterative algorithm to generate custom training forces to "trick" subjects into altering their target-directed reaching movements to a prechosen movement as an after-effect of adaptation. The prechosen movement goal, a sinusoidal-shaped path from start to end point, was never explicitly conveyed to the subject. We hypothesized that the adaptation would cause an alteration in the feedforward command that would result in the prechosen movement. Our results showed that when forces were suddenly removed after a training period of 330 movements, trajectories were significantly shifted toward the prechosen movement. However, de-adaptation occurred (i.e., the after-effect "washed out") in the 50-75 movements that followed the removal of the training forces. A second experiment suppressed vision of hand location and found a detectable reduction in the washout of after-effects, suggesting that visual feedback of error critically influences learning. A final experiment demonstrated that after-effects were also present in the neighborhood of training--44% of original directional shift was seen in adjacent, unpracticed movement directions to targets that were 60 degrees different from the targets used for training. These results demonstrate the potential for these methods for teaching motor skills and for neuro-rehabilitation of brain-injured patients. This is a form of "implicit learning," because unlike explicit training methods, subjects learn movements with minimal instructions, no knowledge of, and little attention to the trajectory.

Adaptation, Physiological↗

PubMed2004

A new postural balance control system for rehabilitation training based on virtual cycling.

A new rehabilitation training system was developed to improve postural balance control by combining virtual reality technology with an unfixed bicycle. Twenty healthy subjects participated in the present study by riding the virtual cycling system under two different conditions: with or without visual feedback. Data were collected on the following parameters: path deviation, cycling velocity, etc. As a result of conducting the repeated training, results showed improvement not only in the ability to control balance and weight shift but also in the overall cycling ability including the degree of path deviation and the cycling speed. It was concluded that the system was effective as a training device and, in addition, the technology might have a wider applicability to the rehabilitation field.

Adult↗

PubMed2004

Development of a biomimetic robotic fish and its control algorithm.

This paper is concerned with the design of a robotic fish and its motion control algorithms. A radio-controlled, four-link biomimetic robotic fish is developed using a flexible posterior body and an oscillating foil as a propeller. The swimming speed of the robotic fish is adjusted by modulating joint's oscillating frequency, and its orientation is tuned by different joint's deflections. Since the motion control of a robotic fish involves both hydrodynamics of the fluid environment and dynamics of the robot, it is very difficult to establish a precise mathematical model employing purely analytical methods. Therefore, the fish's motion control task is decomposed into two control systems. The online speed control implements a hybrid control strategy and a proportional-integral-derivative (PID) control algorithm. The orientation control system is based on a fuzzy logic controller. In our experiments, a point-to-point (PTP) control algorithm is implemented and an overhead vision system is adopted to provide real-time visual feedback. The experimental results confirm the effectiveness of the proposed algorithms.

Algorithms↗