Human arm endpoint-impedance in rhythmic human-robot interaction exhibits cyclic variations.

Estimating the human endpoint-impedance interacting with a physical environment provides insights into goal-directed human movements during physical interactions. This work examined the endpoint-impedance of the upper limb during a hybrid ball-bouncing task with simulated haptic feedback while participants manipulated an admittance-controlled robot. Two experiments implemented a force-perturbation method to estimate the endpoint parameters of 31 participants.

Mechanomyographic Analysis for Muscle Activity Assessment during a Load-Lifting Task.

The purpose of this study was to compare electromyographic (EMG) with mechanomyographic (MMG) recordings during isometric conditions, and during a simulated load-lifting task. Twenty-two males (age: 25.5 ± 5.

Sleep-related motor skill consolidation and generalizability after physical practice, motor imagery, and action observation.

Sleep benefits the consolidation of motor skills learned by physical practice, mainly through periodic thalamocortical sleep spindle activity. However, motor skills can be learned without overt movement through motor imagery or action observation. Here, we investigated whether sleep spindle activity also supports the consolidation of non-physically learned movements.

Voluntary control of pelvic frontal rotations in belly dance experts.

The present study investigated how belly dance experts perform the "hip shimmy", a complex rhythmic dance movement consisting in a voluntary oscillation of the pelvis exclusively in the frontal plane with maximised amplitude, with no movement of the upper trunk. The aims of this study were to 1) assess whether the amplitude and stability of the pelvic movement can be maximised in certain postural and frequency conditions; and 2) investigate in a 1 to 3 Hz range whether it is indeed possible to oscillate the pelvis only in the frontal plane and to dissociate this one-axis pelvic rotation from potential spontaneous upper-trunk oscillations. Nineteen belly dance experts performed this task in three frequencies and three knee bending postures.

Combined Hip Angle Variability and RPE Could Determine Gait Transition in Elite Race Walkers.

The aim of this study was to investigate the role of energy cost in locomotion, specifically the rate of perceived exertion and movement variability in gait transition for eight race walkers (RW) and seven nonrace walkers (NRW). We hypothesized that a group of correlated variables could serve as combined triggers. Participants performed a preferred transition speed (PTS) test, exhibiting a higher PTS for RW (10.

The self-organization of ball bouncing.

The hybrid rhythmic ball-bouncing task considered in this study requires a participant to hit a ball in a virtual environment by moving a paddle in the real environment. It allows for investigation of the online visual control of action in humans. Changes in gravity acceleration in the virtual environment affect the ball dynamics and modify the ball-paddle system limit cycle.

Model of rhythmic ball bouncing using a visually controlled neural oscillator.

The present paper investigates the sensory-driven modulations of central pattern generator dynamics that can be expected to reproduce human behavior during rhythmic hybrid tasks. We propose a theoretical model of human sensorimotor behavior able to account for the observed data from the ball-bouncing task. The novel control architecture is composed of a Matsuoka neural oscillator coupled with the environment through visual sensory feedback.

The embodied dynamics of perceptual causality: a slippery slope?

In Michotte's launching displays, while the launcher (object A) seems to move autonomously, the target (object B) seems to be displaced passively. However, the impression of A actively launching B does not persist beyond a certain distance identified as the "radius of action" of A over B. If the target keeps moving beyond the radius of action, it loses its passivity and seems to move autonomously.

Major changes in a rhythmic ball-bouncing task occur at age 7 years.

The aim of the study was to investigate the development of a rhythmical skill of children aged from 5 to 12 years old. Five age groups (5-6, 7-8, 9-10, 11-12, and young adults) performed a virtual ball bouncing task (16 forty-second long test trials). Task performances, racket oscillation, ball-racket impacts as well as the ball-racket coupling were analysed.

Adaptive tuning of perceptual timing to whole body motion.

In a previous work we have shown that sinusoidal whole-body rotations producing continuous vestibular stimulation, affected the timing of motor responses as assessed with a paced finger tapping (PFT) task (Binetti et al. (2010). Neuropsychologia, 48(6), 1842-1852).

Passive vs. active control of rhythmic ball bouncing: the role of visual information.

The simple task of bouncing a ball on a racket offers a model system for studying how human actors exploit the physics and information of the environment to control their behavior. Previous work shows that people take advantage of a passively stable solution for ball bouncing but can also use perceptual information to actively stabilize bouncing. In this article, we investigate (a) active and passive contributions to the control of bouncing, (b) the visual information in the ball's trajectory, and (c) how it modulates the parameters of racket oscillation.

Time in motion: effects of whole-body rotatory accelerations on timekeeping processes.

The ability of effectively representing time ensures the efficiency and accuracy of sensory and motor processing. It is well documented that in still observers, subjective time varies in response to variations of external sensory inputs. However, it is still poorly understood how inertial inputs, which enable coding of body displacements in space, affect timekeeping processes in a dynamic agent.

Action-perception patterns in virtual ball bouncing: combating system latency and tracking functional validity.

How can we evaluate the spatio-temporal performance of virtual environments (VE) for research use? Here we show that end-to-end latency (ETEL) of VE can strongly damage users' perceptual and perceptuo-motor behaviors and that it can be considered to be the key factor for evaluating face and functional fidelity of a VE. We used a virtual ball-bouncing task as a paradigmatic example. Ball bouncing is known to exhibit attractive and repelling states whose localization in the racket cycle is sufficiently thin to be changed by small variations of ETEL.

Intercepting free falling objects: better use Occam's razor than internalize Newton's law.

Several studies have recently provided empirical data supporting the view that gravity has been embodied in a quantitative internal model of gravity thereby permitting access to exact time-to-contact (TTC) when intercepting a free falling object. In this review, we discuss theoretical and methodological concerns with the experiments that supposedly support the assumption of a predictive and accurate model of gravity. Having done so, we then propose that only a "qualitative implicit physics knowledge" of the effects of gravity is used as an approximate pre-information that influences timing of interceptive actions in the specific case of free falling objects.

Learning new perception-action solutions in virtual ball bouncing.

How do humans discover stable solutions to perceptual-motor tasks as they interact with the physical environment? We investigate this question using the task of rhythmically bouncing a ball on a racket, for which a passively stable solution is defined. Previously, it was shown that participants exploit this passive stability but can also actively stabilize bouncing under perceptual control. Using a virtual ball-bouncing display, we created new behavioral solutions for rhythmic bouncing by introducing a temporal delay (45 degrees -180 degrees ) between the motion of the physical racket and that of the virtual racket.

The "ways" we look at dreams: evidence from unilateral spatial neglect (with an evolutionary account of dream bizarreness).

Despite decades of research, the question of whether the rapid eye movements (REMs) of paradoxical sleep (PS) are equivalent to waking saccades and whether their direction is congruent with visual spatial events in the dream scene is still very controversial. We gained an insight into these questions through the study of a right brain damaged patient suffering attentional neglect for the left side of space and drop of the optokinetic nystagmus (OKN) with alternating rightward slow/leftward fast phases evoked by rightward optic flow. During PS the patient had frequent Nystagmoid REMs with alternating leftward slow/rightward fast phases and reported dreams with visual events evoking corresponding OKN such as a train running leftward.

Effects of vestibular rotatory accelerations on covert attentional orienting in vision and touch.

Peripheral vestibular organs feed the central nervous system with inputs favoring the correct perception of space during head and body motion. Applying temporal order judgments (TOJs) to pairs of simultaneous or asynchronous stimuli presented in the left and right egocentric space, we evaluated the influence of leftward and rightward vestibular rotatory accelerations given around the vertical head-body axis on covert attentional orienting. In a first experiment, we presented visual stimuli in the left and right hemifield.

The importance of head-free gaze control in humans performing a spatial orientation task.

The present study aimed at investigating how a specific instruction concerning gaze orientation, which involved active head motion, could influence the performance of human subjects in a self-controlled whole-body rotation task in the dark. Subjects were seated on a mobile robotic chair that they controlled using a joystick. They were asked to perform 360 degrees rotations while maintaining, when possible, the gaze on the estimated position of an earth-fixed target.

Vestibulo-ocular and optokinetic impairments in left unilateral neglect.

Right brain damaged patients affected by left unilateral neglect (N+) typically fail to explore the contralesional space. For the first time, this study investigates the dynamic and spatial features of the horizontal vestibular-ocular response (VOR), the optokinetic response (OKR) and the VOR-OKR interaction in six N+ and in five right brain damaged patients without neglect (N-). No lateral asymmetry of the gain (i.