Sensory Feedback Control Research Articles

Sensory feedback in cockroach locomotion: current knowledge and open questions.

The American cockroach, Periplaneta americana, provides a successful model for the study of legged locomotion. Sensory regulation and the relative importance of sensory feedback vs. central control in animal locomotion are key aspects in our understanding of locomotive behavior. Here we introduce the cockroach model and describe the basic characteristics of the neural generation and control of walking and running in this insect. We further provide a brief overview of some recent studies, including mathematical modeling, which have contributed to our knowledge of sensory control in cockroach locomotion. We focus on two sensory mechanisms and sense organs, those providing information related to loading and unloading of the body and the legs, and leg-movement-related sensory receptors, and present evidence for the instrumental role of these sensory signals in inter-leg locomotion control. We conclude by identifying important open questions and indicate future perspectives.

An osseointegrated human-machine gateway for long-term sensory feedback and motor control of artificial limbs.

A major challenge since the invention of implantable devices has been a reliable and long-term stable transcutaneous communication. In the case of prosthetic limbs, existing neuromuscular interfaces have been unable to address this challenge and provide direct and intuitive neural control. Although prosthetic hardware and decoding algorithms are readily available, there is still a lack of appropriate and stable physiological signals for controlling the devices. We developed a percutaneous osseointegrated (bone-anchored) interface that allows for permanent and unlimited bidirectional communication with the human body. With this interface, an artificial limb can be chronically driven by implanted electrodes in the peripheral nerves and muscles of an amputee, outside of controlled environments and during activities of daily living, thus reducing disability and improving quality of life. We demonstrate in one subject, for more than 1 year, that implanted electrodes provide a more precise and reliable control than surface electrodes, regardless of limb position and environmental conditions, and with less effort. Furthermore, long-term stable myoelectric pattern recognition and appropriate sensory feedback elicited via neurostimulation was demonstrated. The opportunity to chronically record and stimulate the neuromuscular system allows for the implementation of intuitive control and naturally perceived sensory feedback, as well as opportunities for the prediction of complex limb motions and better understanding of sensory perception. The permanent bidirectional interface presented here is a critical step toward more natural limb replacement, by combining stable attachment with permanent and reliable human-machine communication.

Human hip–ankle coordination emerging from multisensory feedback control

Human sensorimotor control involves inter-segmental coordination to cope with the complexity of a multi-segment system. The combined activation of hip and ankle muscles during upright stance represents the hip–ankle coordination. This study postulates that the coordination emerges from interactions on the sensory levels in the feedback control. The hypothesis was tested in a model-based approach that compared human experimental data with model simulations. Seven subjects were standing with eyes closed on an anterior–posterior tilting motion platform. Postural responses in terms of angular excursions of trunk and legs with respect to vertical were measured and characterized using spectral analysis. The presented control model consists of separate feedback modules for the hip and ankle joints, which exchange sensory information with each other. The feedback modules utilize sensor-derived disturbance estimates rather than ‘raw’ sensory signals. The comparison of the human data with the simulation data revealed close correspondence, suggesting that the model captures important aspects of the human sensory feedback control. For verification, the model was re-embodied in a humanoid robot that was tested in the human laboratory. The findings show that the hip–ankle coordination can be explained by interactions between the feedback control modules of the hip and ankle joints.

Humans can integrate feedback of discrete events in their sensorimotor control of a robotic hand.

Providing functionally effective sensory feedback to users of prosthetics is a largely unsolved challenge. Traditional solutions require high band-widths for providing feedback for the control of manipulation and yet have been largely unsuccessful. In this study, we have explored a strategy that relies on temporally discrete sensory feedback that is technically simple to provide. According to the Discrete Event-driven Sensory feedback Control (DESC) policy, motor tasks in humans are organized in phases delimited by means of sensory encoded discrete mechanical events. To explore the applicability of DESC for control, we designed a paradigm in which healthy humans operated an artificial robot hand to lift and replace an instrumented object, a task that can readily be learned and mastered under visual control. Assuming that the central nervous system of humans naturally organizes motor tasks based on a strategy akin to DESC, we delivered short-lasting vibrotactile feedback related to events that are known to forcefully affect progression of the grasp-lift-and-hold task. After training, we determined whether the artificial feedback had been integrated with the sensorimotor control by introducing short delays and we indeed observed that the participants significantly delayed subsequent phases of the task. This study thus gives support to the DESC policy hypothesis. Moreover, it demonstrates that humans can integrate temporally discrete sensory feedback while controlling an artificial hand and invites further studies in which inexpensive, noninvasive technology could be used in clever ways to provide physiologically appropriate sensory feedback in upper limb prosthetics with much lower band-width requirements than with traditional solutions.

Stance width changes how sensory feedback is used for multisegmental balance control.

A multilink sensorimotor integration model of frontal plane balance control was developed to determine how stance width influences the use of sensory feedback in healthy adults. Data used to estimate model parameters came from seven human participants who stood on a continuously rotating surface with three different stimulus amplitudes, with eyes open and closed, and at four different stance widths. Dependent variables included lower body (LB) and upper body (UB) sway quantified by frequency-response functions. Results showed that stance width had a major influence on how parameters varied across stimulus amplitude and between visual conditions. Active mechanisms dominated LB control. At narrower stances, with increasing stimulus amplitude, subjects used sensory reweighting to shift reliance from proprioceptive cues to vestibular and/or visual cues that oriented the LB more toward upright. When vision was available, subjects reduced reliance on proprioception and increased reliance on vision. At wider stances, LB control did not exhibit sensory reweighting. In the UB system, both active and passive mechanisms contributed and were dependent on stance width. UB control changed across stimulus amplitude most in wide stance (opposite of the pattern found in LB control). The strong influence of stance width on sensory integration and neural feedback control implies that rehabilitative therapies for balance disorders can target different aspects of balance control by using different stance widths. Rehabilitative strategies designed to assess or modify sensory reweighting will be most effective with the use of narrower stances, whereas wider stances present greater challenges to UB control.

CPG-based Sensory Feedback Control for Bio-inspired Multimodal Swimming

Sensory feedback plays a very significant role in the generation of diverse and stable movements for animals. In this paper we describe our effort to develop a Central Pattern Generator (CPG)-based sensory feedback control for the creation of multimodal swimming for a multi-articulated robotic fish in the context of neurocomputing. The proposed control strategy is composed of two phases: the upper decision-making and the automatic adjustment. According to the upper control commands and the sensory inputs, different swimming gaits are determined by a finite state machine algorithm. At the same time, the sensory feedback is exploited to shape the CPG coupling forms and control parameters. In the automatic adjustment phase, the CPG model with sensory feedback will adapt the environment autonomously. Simulation and underwater tests are further conducted to verify the presented control scheme. It is found that the CPG-based sensory feedback control method can effectively improve the manoeuvrability and adaptability of the robotic fish in water.

Modeling and Simulations of Biomechanical Symptoms of Parkinson's Disease

Patients with Parkinson's disease experience oscillatory motion of body parts (tremor) due to an increased reaction time. The tremor is an early-stage symptom of Parkinson's disease, but the increased reaction time (the delay in the sensory feedback control) can make it difficult for patients to perform their basic tasks. Biomechanical models with feedback control theory can not only provide diagnostic tools to measure the delay from the nature of tremor, but can also provide a quantitative understanding of how the delay results in other advanced-stage biomechanical symptoms such as stooping. A mechanics-based perspective on how the tremor results from the delay has recently been proposed in [J. Mech. Med. Biol., Vol. 11(5), pp.1017]. We extended the same perspective to develop a proof-of-concept smartphone App for measuring the severity of the disease in terms of the delay from the tremor. We are also developing mechanical models of human body with neural control based on the same perspective to simulate and analyze other biomechanical symptoms of the disease. We expect that such models will provide a novel foundation for improved diagnosis, prognosis, and safer symptomatic treatment strategies.

Effects of vocal training on voluntary responses to pitch-shifted voice auditory feedback

Control of voice fundamental frequency (F0) relies on the interaction between various forms of sensory feedback and neural motor control mechanisms. Several studies have shown that unexpected changes in pitch in the auditory feedback lead to reflexive compensatory vocal responses. We examined voluntary vocal responses to unpredictable perturbations in pitch auditory feedback. Ten subjects were trained over a five-day period to change their voice F0 in the opposite direction to the pitch-shifted feedback (±100 cents, 1000 ms) and 10 in the same direction as the feedback. Results showed that responses that followed the stimulus direction had significantly shorter latencies (200 ms) than opposing responses (324 ms). The reduced latency of the following responses suggests a switch from a feedback to a feedforward control strategy. The feedback strategy requires monitoring feedback and correcting for errors between the feedback signal and the intended vocal goal. The feedforward strategy relies less on auditory feedback and more on an internal model of the desired vocal pitch goal. Furthermore, feedback systems generally are slower than feedforward strategies, which would explain the shorter latencies of the responses that followed the stimulus direction. Results of this study will be discussed in terms of the differing strategies that may be used in various vocal contexts.

Limit-cycle-based control of the myogenic wingbeat rhythm in the fruit flyDrosophila

In many animals, rhythmic motor activity is governed by neural limit cycle oscillations under the control of sensory feedback. In the fruit flyDrosophila melanogaster, the wingbeat rhythm is generated myogenically by stretch-activated muscles and hence independently from direct neural input. In this study, we explored if generation and cycle-by-cycle control ofDrosophila's wingbeat are functionally separated, or if the steering muscles instead couple into the myogenic rhythm as a weak forcing of a limit cycle oscillator. We behaviourally tested tethered flying flies for characteristic properties of limit cycle oscillators. To this end, we mechanically stimulated the fly's ‘gyroscopic’ organs, the halteres, and determined the phase relationship between the wing motion and stimulus. The flies synchronized with the stimulus for specific ranges of stimulus amplitude and frequency, revealing the characteristic Arnol'd tongues of a forced limit cycle oscillator. Rapid periodic modulation of the wingbeat frequency prior to locking demonstrates the involvement of the fast steering muscles in the observed control of the wingbeat frequency. We propose that the mechanical forcing of a myogenic limit cycle oscillator permits flies to avoid the comparatively slow control based on a neural central pattern generator.

Metabolic efficiency of volitional and electrically stimulated cycling in able-bodied subjects

This study compared the metabolic efficiency of volitional cycling and functional-electrical-stimulation (FES) cycling within a subject group of able-bodied individuals, with a view to further elucidating the mechanisms underlying the low efficiency of FES cycling. Previous studies estimated the metabolic efficiency of volitional cycling and anaesthetised FES cycling in able-bodied subjects, and of FES cycling in subjects paralysed by spinal cord injury.The rationale for the experimental model chosen here, i.e. non-anaesthetised able-bodied subjects, was that this lies between normal cycling and paralysed cycling: while using FES, this group has artificial muscle activation and timing like the paralysed group; but it does not have disrupted sensory feedback and vasomotor control; this measurement therefore allows delineation of the magnitude of reduction in metabolic efficiency resulting from: (i) the FES itself and (ii) paralysis (where there is disrupted sensory feedback and vasomotor control). Furthermore, we used the same methods employed previously for estimation of metabolic efficiency in subjects with motor- and sensory-complete paraplegia.The mean metabolic efficiency of volitional cycling was found to be 29.8% and that of FES cycling was 16.4% (n=11).The low efficiency of FES cycling can be explained in large part by the crude timing of muscle activation and by non-physiological muscle fibre recruitment. In FES cycling with paralysed subjects, disrupted sensory feedback and vasomotor control may play a further, albeit smaller, role in the reduced efficiency.

Differential effects of absent visual feedback control on gait variability during different locomotion speeds

Healthy persons exhibit relatively small temporal and spatial gait variability when walking unimpeded. In contrast, patients with a sensory deficit (e.g., polyneuropathy) show an increased gait variability that depends on speed and is associated with an increased fall risk. The purpose of this study was to investigate the role of vision in gait stabilization by determining the effects of withdrawing visual information (eyes closed) on gait variability at different locomotion speeds. Ten healthy subjects (32.2±7.9years, 5 women) walked on a treadmill for 5-min periods at their preferred walking speed and at 20, 40, 70, and 80% of maximal walking speed during the conditions of walking with eyes open (EO) and with eyes closed (EC). The coefficient of variation (CV) and fractal dimension (α) of the fluctuations in stride time, stride length, and base width were computed and analyzed. Withdrawing visual information increased the base width CV for all walking velocities (p<0.001). The effects of absent visual information on CV and α of stride time and stride length were most pronounced during slow locomotion (p<0.001) and declined during fast walking speeds. The results indicate that visual feedback control is used to stabilize the medio-lateral (i.e., base width) gait parameters at all speed sections. In contrast, sensory feedback control in the fore-aft direction (i.e., stride time and stride length) depends on speed. Sensory feedback contributes most to fore-aft gait stabilization during slow locomotion, whereas passive biomechanical mechanisms and an automated central pattern generation appear to control fast locomotion.

Adaptive Excitation Control for the Underactuated Biped Robot

A control method to make the chaotic gait converge to a stable cycle gait is proposed for the biped robot with knees. This control method is called adaptive excitation control. It is based on the principle of bionics and the principle of self-excited. The control law is a combination of sinusoidal input and sensory feedback control. The control torque is only inputted into the robot's hip. Therefore, the walking process is low energy consuming. Simulation results show that the control method proposed in this paper is effective. It can enlarge the basin of attraction of limit cycle and increase the gait stability.

On the applicability of the decentralized control mechanism extracted from the true slime mold: a robotic case study with a serpentine robot

A systematic method for an autonomous decentralized control system is still lacking, despite its appealing concept. In order to alleviate this, we focused on the amoeboid locomotion of the true slime mold, and extracted a design scheme for the decentralized control mechanism that leads to adaptive behavior for the entire system, based on the so-called discrepancy function. In this paper, we intensively investigate the universality of this design scheme by applying it to a different type of locomotion based on a ‘synthetic approach’. As a first step, we implement this design scheme to the control of a real physical two-dimensional serpentine robot that exhibits slithering locomotion. The experimental results show that the robot exhibits adaptive behavior and responds to the environmental changes; it is also robust against malfunctions of the body segments due to the local sensory feedback control that is based on the discrepancy function. We expect the results to shed new light on the methodology of autonomous decentralized control systems.

Verletzungsprävention durch Verbesserung der neuromuskulären Bewegungskontrolle

The fact that existing prevention strategies still cause sustained high injury rates and health disorders in performance sports should result in a critical view on the current methods. In the last 20 years, research in soccer showed that injury rates could not be reduced despite the use of several interventions with different motor control techniques. Own investigations prove that prolonged peripheral and central fatigue is a predictor for the development of overload damage and injuries. EEG-data indicate a relation between the activity of the motor system in the brain, the sensory feedback control system and muscular fatigue. Furthermore, this data implies that injury prevention can be achieved through an optimization of the neuromuscular control of joint movements. Apparently, firm movement patterns in combination with different pressure situations and highly intensive load situations have to be trained in order to optimize motor control and to decode abnormal central regulations. To prevent abnormal regulations, the link between cognition and action should be the basis for a new kind of sport-specific athletic training. The acquired exercises should be part of every warm-up routine to facilitate a faster and more appropriate reaction to new situations.

The specific origin of the simple and complex spikes in Purkinje neurons

The specific origin of the simple and complex spikes in Purkinje neurons

Development of Closed-Loop Neural Interface Technology in a Rat Model: Combining Motor Cortex Operant Conditioning With Visual Cortex Microstimulation

Closed-loop neural interface technology that combines neural ensemble decoding with simultaneous electrical microstimulation feedback is hypothesized to improve deep brain stimulation techniques, neuromotor prosthetic applications, and epilepsy treatment. Here we describe our iterative results in a rat model of a sensory and motor neurophysiological feedback control system. Three rats were chronically implanted with microelectrode arrays in both the motor and visual cortices. The rats were subsequently trained over a period of weeks to modulate their motor cortex ensemble unit activity upon delivery of intra-cortical microstimulation (ICMS) of the visual cortex in order to receive a food reward. Rats were given continuous feedback via visual cortex ICMS during the response periods that was representative of the motor cortex ensemble dynamics. Analysis revealed that the feedback provided the animals with indicators of the behavioral trials. At the hardware level, this preparation provides a tractable test model for improving the technology of closed-loop neural devices.

1A1-F02 局所的な齟齬情報に基づくヘビ型ロボットの適応的自律分散制御方策

A systematic way of designing autonomous decentralized control system is still lacking, despite its appealing concept. In order to alleviate this, we have so far proposed a design scheme for autonomous decentralized control leading to adaptive behaviors from the entire system, based on a so-called discrepancy function that extracts the discrepancies between body (i.e., mechanical system), brain (i.e., control system) and environments. This paper intensively investigates the validity of this design scheme under the real world constraints by taking a two-dimensional serpentine robot exhibiting undulatory slithering locomotion as a practical example. The experimental results show that the robot exhibits adaptive behavior against environmental changes as well as the robustness against malfunctions of body segments due to the local sensory feedback control. The results obtained are expected to shed a new light on methodology for autonomous decentralized control system.

Skill Transfer from Human to Robot by Direct Teaching and Task Sharing -A Case Study with Origami Folding Task-

Manipulation skill, which is a sort of implicit knowledge, is very ***di cult to be transfered even among humans. Skill transfer from human to robot is even more di cult because humans and robots have dissimilar bodies. The authors already proposed a novel method to transfer manipulation skill from a human to a robot by direct teaching. A Hidden Markov Model (HMM) was employed to model the statistical characteristics of the teaching data demonstrated by a human. A nominal trajectory and sensory feedback control laws were extracted from the statistical characteristics of the trained HMM. In this paper, a new method to extract sensory feedback control laws by direct teaching is proposed. The proposed method fully takes the statistical information of the teaching data from the canonical correlations between force (sensing) and velocity (action). Then, sensory feedback control laws, whose weighting factors have temporal continuity and directional dependency, are constructed without introducing any threshold values which had to be determined by trial and error in the previous method. Like the previous study by the authors, the proposed method is applied to an origami-folding task and experimental results show that the success rate and the folding quality of ‘Valley-fold’ are improved. It is shown that task sharing by direct teaching is a key to successfully transferring manipulation skills between human and robot who have dissimilar bodies.

Softly Elastic 6 DOF Input

The aim of this work is to identify the properties that a universal multidimensional input device should have in order to optimally function with 3D applications, including Web browsers, window managers, digital content creation software, and computer games. Such applications have become increasingly effective due to the rapid development of computer graphics. This situation has generated a greater need for multidimensional input devices. It is conjectured that an ideal universal multidimensional input device should allow for 2D pointing as well as precise manipulation and navigation within 3D environments. Accordingly, the device should offer (a) six degrees of freedom, (b) a range of motion adapted to finger manipulation, (c) elastic suspension providing rich sensory feedback, and (d) position and rate control. The input device, SpaceCat, was designed to offer all these properties. Although such devices are known to benefit 3D navigation, this work demonstrates that they also benefit 3D object manipulation.

Sensory feedback dependence hypothesis in persons who stutter

The present study investigated the role of sensory feedback (auditory, proprioception, and tactile) at the intra- and inter-gestural levels of speech motor coordination in normal and fast speech rate conditions in two groups: (1) persons who stutter (PWS) and (2) those who do not (PNS). Feedback perturbations were carried out with the use of masking noise (auditory), tendon vibration (proprioception), and nonwords that differed in the amount of required tactile lip contact (/api/ + tactile and /awi/ − tactile). Comparisons were also made between jaw-free and jaw-immobilized (with a bite-block) task conditions. It was hypothesized that if PWS depend more strongly on sensory feedback control during speech production, they would show an increase in variability of movement coordination in the combined presence of fast speech rates and feedback perturbations, in particular, when jaw motions are blocked and adaptations in the other articulators are required to achieve the task goals. Significant feedback perturbation effects were found for both groups, but the only significant between-group effect was found at fast speech rates in the jaw-free condition, showing that control speakers were more perturbed at the intra-gestural level of coordination than PWS when simultaneous (auditory, proprioceptive, and tactile) perturbations were present. The findings do not provide support for either the feedback dependency or the sensory deficit hypotheses described in the literature to explain movement characteristics found in fluent speech production of PWS.