1,720,994 research outputs found
COMAP: a new computational interpretation of human movement planning level based on coordinated minimum angle jerk policies and six universal movement elements.
No full textThe purpose of this work is to develop a computational model to describe the task of sit to stand (STS). STS is an important movement skill which is frequently performed in human daily activities, but has rarely been studied from the perspective of optimization principles. In this study, we compared the recorded trajectories of STS with the trajectories generated by several conventional optimization-based models (i.e., minimum torque, minimum torque change and kinetic energy cost models) and also with the trajectories produced by a novel multi-phase cost model (MPCM). In the MPCM, we suggested that any complex task, such as STS, is decomposable into successive motion phases, so that each phase requires a distinct strategy to be performed. In this way, we proposed a multi-phase cost function to describe the STS task. The results revealed that the conventional optimization-based models failed to correctly predict the invariable features of STS, such as hip flexion and ankle dorsiflexion movements. However, the MPCM not only predicted the general features of STS with a sufficient accuracy, but also showed a potential flexibility to distinguish between the movement strategies from one subject to the other. According to the results, it seems plausible to hypothesize that the central nervous system might apply different strategies when planning different phases of a complex task. The application areas of the proposed model could be generating optimized trajectories of STS for clinical applications (such as functional electrical stimulation) or providing clinical and engineering insights to develop more efficient rehabilitation devices and protocols
Enhancing gait cadence through rhythm-modulated music: A study on healthy adults
No full textBackground and objective: Gait disorders stemming from brain lesions or chemical imbalances, pose significant challenges for patients. Proposed treatments encompass medication, deep brain stimulation, physiotherapy, and visual stimulation. Music, with its harmonious structures, serves as a continuous reference, synchronizing muscle activities through neural connections between hearing and motor functions, can show promise in gait disorder management. This study explores the influence of heightened music rhythm on young healthy participants' gait cadence in three conditions: FeedForward (independent rhythm), FeedBack (cadence-synced rhythm), and Adaptive (cadence-controlled musical experience). The objective is to increase gait cadence through rhythm modulation during walking. Method: The study involved 18 young healthy participants (13 males and 5 females) who did not have any gait or hearing disorders. Each participant completed the gait task in the three aforementioned conditions. Each condition was comprised of three sessions: 1) Baseline, where participants walked while listening to the original music; 2) Intervention, changing the music rhythm to affect the gait cadence; and 3) Realign, replaying the original music and measuring the durability of the effect of the Intervention session. The measurement tool was a pair of footwear equipped with push-button switches that transmited the foot-to-ground contact to the LabVIEW® software, all designed by the research team. Repeated measures of ANOVA was employed to evaluate the impact of the sessions and conditions. Results: In all three conditions, there was a significant effect of music on increasing gait cadence during Intervention and Realign sessions (p < 0.001). Additionally, the immediate impact of music on gait cadence in the Adaptive condition was superior to the other conditions. Conclusion: The study findings indicate that increasing the rhythm of music during walking has a significant impact on gait cadence among young healthy participants. This effect remained significant even after realigning the music to normal. It could be harnessed to support the rehabilitation of individuals with movement disorders characterized by a decrease in movement speed, such as Parkinson's disease. Moreover, the results indicate that the Adaptive method showed promising outcomes, suggesting its potential for further exploration as an effective means to control gait cadence
Trajectory of human movement during sit to stand: a new modeling approach based on movement decomposition and multi-phase cost function.
No full textThe purpose of this work is to develop a computational model to describe the task of sit to stand (STS). STS is an important movement skill which is frequently performed in human daily activities, but has rarely been studied from the perspective of optimization principles. In this study, we compared the recorded trajectories of STS with the trajectories generated by several conventional optimization-based models (i.e., minimum torque, minimum torque change and kinetic energy cost models) and also with the trajectories produced by a novel multi-phase cost model (MPCM). In the MPCM, we suggested that any complex task, such as STS, is decomposable into successive motion phases, so that each phase requires a distinct strategy to be performed. In this way, we proposed a multi-phase cost function to describe the STS task. The results revealed that the conventional optimization-based models failed to correctly predict the invariable features of STS, such as hip flexion and ankle dorsiflexion movements. However, the MPCM not only predicted the general features of STS with a sufficient accuracy, but also showed a potential flexibility to distinguish between the movement strategies from one subject to the other. According to the results, it seems plausible to hypothesize that the central nervous system might apply different strategies when planning different phases of a complex task. The application areas of the proposed model could be generating optimized trajectories of STS for clinical applications (such as functional electrical stimulation) or providing clini
The somatosensory temporal discrimination threshold changes after a placebo procedure
No full textIn a recent study, we showed that tactile perception can be enhanced by applying a placebo manipulation consisting of verbal suggestion and conditioning (Fiorio et al., Neuroscience 217:96-104, 2012). Whether this change in perception is related to a better tactile functioning is still unknown. Aim of this study is to investigate whether placebo-induced enhancement of tactile perception results in better somatosensory temporal discrimination threshold (STDT), as a proxy of tactile acuity. To this purpose, a group of subjects (experimental group) was verbally influenced and conditioned about the effect of an inert cream in enhancing tactile perception, while a control group was informed about the real nature of the cream. In both groups, we measured STDT before and after cream application, by means of pairs of electrical stimuli delivered on the index fingertip and separated by ascending inter-stimulus intervals. STDT was defined as the shortest time interval at which the two stimuli were perceived as separated. Results revealed an increase in subjective perception of stimulus intensity and a reduction of STDT only in the experimental group. This study proves that a placebo procedure, consisting of verbal suggestion and a short conditioning, can reduce the temporal discrimination threshold
Spinal reflexive movement follows general tau theory
Get PDFBackground: Tau theory explains how both intrinsically and perceptually guided movements are controlled by the brain. According to general tau theory, voluntary, self-paced human movements are controlled by coupling the tau of the movement (i.e., the rate of closure of the movement gap at its current closure rate) onto an intrinsically generated tau-guide (Lee in Ecol Psychol 10:221-250, 1998). To date there are no studies that have looked at involuntary movements, which are directly guided by innate patterns of neural energy generated at the level of the spinal cord or brain, and that can be explained by general tau theory. This study examines the guidance of an involuntary movement generated by the Patellar reflex in presence of a minimized gravitational field. Results: The results showed that the Patellar reflexive movement is strongly coupled to an intrinsic tau-guide particularly when the limb is not moving in the direction of gravity. Conclusion: These results suggest that the same principles of control underpin both voluntary and involuntary movements irrespective of whether they are generated in the brain or the spinal cord. Secondly, given that movements like the patellar reflex are visible from infancy, one might conclude that tau-guidance is an innate form of motor control, or neural blueprint, that has evolved over time. Keywords: Gravitational field; Involuntary movements; Movement planning; Patellar reflex; Tau theor
General tau theory as a model to evaluate audiovisual interplay in interceptive actions
Get PDFWhen interacting with the environment, sensory information is essential to guide movements. Picking up the appropriate sensory information (both visual and auditory) about the progression of an event is required to reach the right place at the right time. In this study, we aimed to see if general tau theory could explain the audiovisual guidance of movement in interceptive action (an interception task). The specific contributions of auditory and visual sensory information were tested by timing synchronous and asynchronous audiovisual interplays in successful interceptive trials. The performance was computed by using the tau-coupling model for information- movement guidance. Our findings revealed that while the auditory contribution to movement guidance did change across conditions, the visual contribution remained constant. In addition, when comparing the auditory and visual contributions, the results revealed a significant decrease in the auditory compared to the visual contribution in just one of the asynchronous conditions where the visual target was presented after the sound. This may be because more attention was drawn to the visual information, resulting in a decrease in the auditory guidance of movement. To summarize, our findings reveal how tau-coupling can be used to disentangle the relative contributions of the visual and auditory sensory modalities in movement planning
The placebo effect shortens movement time in goal-directed movements
Get PDFThe placebo effect is a powerful psychobiological phenomenon whereby a positive outcome follows the administration of an inert treatment thought to be effective. Growing evidence shows that the placebo effect extends beyond the healing context, affecting also motor performance. Here we explored the placebo effect on the control of goal-directed movement, a fundamental function in many daily activities. Twenty-four healthy volunteers performed upper-limb movements toward a target at different indexes of difficulty in two conditions: in the placebo condition, an electrical device (inert) was applied to the right forearm together with verbal information about its positive effects in improving movement precision; in the control condition, the same device was applied along with verbal information about its neutral effects on performance. Interestingly, we found shorter movement time in the placebo compared to the control condition. Moreover, subjective perception of fatigability was reduced in the placebo compared to the control condition. These findings indicate that the placebo effect can improve the execution of goal-directed movements, thus adding new evidence to the placebo effect in the motor domain. This study could inspire future applications to improve upper-limb movements or in clinical settings for patients with motor deficits
A bio-inspired modular hierarchical structure to plan the sit-to-stand transfer under varying environmental conditions
No full textHuman motion planning studies are of considerable importance in producing human-like trajectories for various industrial or clinical applications (e.g. assistive robots). In this case, the capability of Central Nervous System (CNS) in generating a large repertoire of actions can be inspirational to develop more efficient motion planning approaches. Here, inspired by structural and functional modularity in the CNS, a novel modular and hierarchical model is developed to plan the sit-to-stand (STS) transfer under varying environmental conditions. In this model, the planning process is distributed among several functionally simple modules. The cooperation of modules enables the model to plan the motion under a variety of conditions. The proposed model is assessed by planning the STS transfer under two types of environmental conditions: varying seat heights and varying base of support areas. The results revealed a suitable fit between the planned trajectories and the experimental trajectories for different conditions. It is demonstrated that a modular motion planner provides a higher accuracy and flexibility for the model to extend the planning process to various new conditions, yet still requires less computational complexity when compared with previous approaches. The proposed model is also supported by several behavioral and neurophysiological evidences
AMA-MOSAICI: An automatic module assigning hierarchical structure to control human motion based on movement decomposition
No full textIn this study, a hierarchical structure is proposed to model human movement control during sit-to-stand transfer. At the highest level the desired movement is planned. Then, the task to be performed is decomposed to its constitutive sub-tasks. To decompose the sit-to-stand movement, the spatial trajectory of the body center of mass is automatically approximated by partially linearized trajectories. Each linearized part defines a sub-task. At the second level, corresponding to each sub-task a module is developed that learns to control the movement during the performance of that sub-task. Since the procedure of decomposition is performed automatically, the number of modules and assessment of suitable data to train the modules are also determined automatically. This feature is one of the main differences between the proposed structure and the MOdular Selection And Identification for Control (MOSAIC) structure [M. Haruno, D.M. Wolpert, M. Kawato, MOSAIC model for sensorimotor learning and control, Neural Computation 13 (2001) 2201–2220.]. Our proposed model is in conformity with the recent physiological and neurobehavioral findings and provides a framework for examining a given movement under different conditions
The role of the dorsolateral prefrontal cortex in the motor placebo effect
No full textThe neural correlates of the placebo effect in the motor domain are still unknown. The aim of this study was to tackle the role of a frontal cortical region, the dorsolateral prefrontal cortex (dlPFC). To this end, we stimulated the cortical site corresponding to the left dlPFC with transcranial direct current stimulation (tDCS) during a placebo procedure and measured any change in the motor placebo effect in all the participants and more specifically in placebo-responders. Three different experiments were conducted in which healthy volunteers performed a force motor task with the index finger. The placebo treatment consisted of transcutaneous electrical nerve stimulation (TENS). In Experiment 1 (expectation alone), participants were only verbally suggested about the positive effects of TENS. In Experiment 2 (expectation and conditioning), participants were verbally suggested about TENS and conditioned with a surreptitious increase of a visual feedback of force. In Experiment 3 (control procedure), participants were told that TENS was inefficient. Each participant was tested in three different days with anodal, cathodal and sham tDCS over the dlPFC. Results showed that in Experiment 1 and 2 force increased after the procedure, independently of tDCS. By focusing on placebo-responders, we found that in Experiment 1 force remained stable after active tDCS, whereas it increased after inactive tDCS. These findings bring new evidence on the neural underpinnings of the motor placebo effect, by showing that independently of the polarity, active tDCS over the left dlPFC may undermine the expectation-induced enhancement of force in placebo-responders. This article is protected by copyright. All rights reserved
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