Olivier WhiteUniversity of Burgundy | UB · Laboratoire Motricité-Plasticité
Olivier White
Ir, PhD
About
74
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1,281
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Introduction
Additional affiliations
September 2010 - present
Freelance consultant
Position
- Consultant
September 2010 - present
September 2010 - present
Education
September 2002 - June 2007
Publications
Publications (74)
The two-thirds power law is a link between angular speed $\omega$ and curvature $\kappa$ observed in voluntary human movements: $\omega$ is proportional to $\kappa^{2/3}$. Squared jerk is known to be a Lagrangian leading to the latter law. We propose that a broader class of higher-derivative Lagrangians leads to the two-thirds power law and we perf...
The human body exploits its neural mechanisms to optimize actions. Rhythmic movements are optimal when their frequency is close to the natural frequency of the system. In a pendulum, gravity modulates this spontaneous frequency. Participants unconsciously adjust their natural pace when cyclically moving the arm in altered gravity. However, the time...
The ability to move is a vital and essential feature of human existence. We are experts at producing varied movement and have refined their control through evolution. As gravity is a major feature of our every-day environment, we have learned to take advantage of it by optimising its effects to minimise the cost of our actions. This can be illustra...
We investigated the influence of the time-of-day and sleep on skill acquisition (i.e., skill improvement immediately after a training-session) and consolidation (i.e., skill retention after a time interval including sleep). Three groups were trained at 10 a.m. (G10 am ), 3 p.m. (G3 pm ), or 8 p.m. (G8 pm ) on a finger-tapping task. We recorded the...
Space exploration objectives will soon move from low Earth orbit to distant destinations like Moon and Mars. The present work provides an up-to-date roadmap that identifies critical research gaps related to human behavior and performance in altered gravity and space. The roadmap summarizes (1) key neurobehavioral challenges associated with spacefli...
As space exploration missions move from low orbit to distant destinations, including the Moon and Mars, new psychological, behavioral, and team challenges will arise. This manuscript represents an up-to-date white paper developed by European experts invited by the European Space Agency (ESA), mapping unfilled research gaps related to the psychology...
When a Hamiltonian system undergoes a stochastic, time-dependent anharmonic perturbation, the values of its adiabatic invariants as a function of time follow a distribution whose shape obeys a Fokker–Planck equation. The effective dynamics of the body’s centre-of-mass during human walking is expected to represent such a stochastically perturbed dyn...
When a Hamiltonian system undergoes a stochastic, time-dependent anharmonic perturbation, the values of its adiabatic invariants as a function of time follow a distribution whose shape obeys a Fokker-Planck equation. The effective dynamics of the body's centre-of-mass during human walking is expected to represent such a stochastically perturbed dyn...
While the time-of-day significantly impacts motor performance, its effect on motor learning has not yet been elucidated. Here, we investigated the influence of the time-of-day on skill acquisition (i.e., skill improvement immediately after a training-session) and consolidation (i.e., skill retention after a time interval). Three groups were trained...
Human walking exhibits properties of global stability, and local dynamic variability, predictability, and complexity. Global stability is typically assessed by quantifying the whole-body center-of-mass motion while local dynamic variability, predictability, and complexity are assessed using the stride interval. Recent arguments from general mechani...
Skilled movements result from a mixture of feedforward and feedback mechanisms conceptualized by internal models. These mechanisms subserve both motor execution and motor imagery. Current research suggests that imagery allows updating feedforward mechanisms, leading to better performance in familiar contexts. Does this still hold in radically new c...
The human sensorimotor control has evolved in the Earth’s environment where all movement is influenced by the gravitational force. Changes in this environmental force can severely impact the performance of arm movements which can be detrimental in completing certain tasks such as piloting or controlling complex vehicles. For this reason, subjects t...
Our sensorimotor control is well adapted to normogravity environment encountered on Earth and any change in gravity significantly disturbs our movement. In order to produce appropriate motor commands for aimed arm movements such as pointing or reaching, environmental changes have to be taken into account. This adaptation is crucial when performing...
The role of gravity in human motor control is at the same time obvious and difficult to isolate. It can be assessed by performing experiments in variable gravity. We propose that adiabatic invariant theory may be used to reveal nearly conserved quantities in human voluntary rhythmic motion, an individual being seen as a complex time-dependent dynam...
Multiple transitions between gravity levels will occur during planetary exploration missions. In reaction to these gravitational transitions, physiological adaptation will be initiated. However, the physiological effects of long-duration exposures to hypogravity and hypergravity are poorly understood. In this review we present an overview of how hu...
Background:
Lymphedema arises due to a malfunction of the lymphatic system, leading to extensive tissue swelling. Complete decongestive therapy (CDT), which is a physical therapy lasting for 3 weeks and includes manual lymphatic drainages (MLD), leads to fluid mobilization and increases in plasma volume. Here, we investigated hemodynamic responses...
Before and immediately after passive upper limb neurodynamic mobilizations targeting the median nerve, grip (G F) and load (L F) forces applied by the thumb, index and major fingers (three-jaw chuck pinch) were collected using a manipulandum during three different grip precision tasks: grip-lift-hold-replace (GLHR), vertical oscillations (OSC), and...
The role of gravity in human motor control is at the same time obvious and difficult to isolate. It can be assessed by performing experiments in variable gravity. We propose that adiabatic invariant theory may be used to reveal nearly-conserved quantities in human voluntary rhythmic motion, an individual being seen as a complex time-dependent dynam...
Movements rely on a mixture of feedforward and feedback mechanisms. With experience, the brain builds internal representations of actions in different contexts. Many factors are taken into account in this process among which is the immutable presence of gravity. Any displacement of a massive body in the gravitational field generates forces and torq...
Le système neurosensoriel est une partie du système nerveux responsable du traitement des informations sensorielles. Un système sensoriel est constitué de neurones sensoriels (y compris les cellules des récepteurs sensoriels), de voies neuronales et de parties du cerveau impliquées dans la perception. Les systèmes sensoriels couramment reconnus son...
Indices characterising the long-range temporal structure of walking stride interval (SI) variability such as Hurst exponent (H) and fractal dimension (D) may be used in addition to indices measuring the amount of variability like the coefficient of variation (CV). We assess the added value of the former indices in a clinical neurological context. O...
Voluntary human movements are stereotyped. When modeled in the framework of classical mechanics they are expected to minimize cost functions that may include energy, a natural candidate from a physiological point of view also. In time-changing environments, however, energy is no longer conserved-regardless of frictional energy dissipation-and it is...
Humans excel at learning complex tasks and elite performers such as musicians or sportsmen develop motor skills that defy biomechanical constraints. All actions require the movement of massive bodies. Of particular interest in the process of sensorimotor learning and control is the impact of gravitational forces on the body. Indeed, efficient contr...
Prism adaptation is a well-known experimental procedure to study sensorimotor plasticity. It has been shown that following prism exposure, after-effects are not only restricted to the sensorimotor level but extend as well to spatial cognition. In the present study, we used a visuo-motor rotation task which approaches the perturbations induced by pr...
Fine dexterity critically depends on information conveyed by the median nerve. While the effects of its compression and vibration are well characterized, little is known about longitudinal tension and excursion. Using a force-sensitive manipulandum, a numeric dynamometer and Semmes-Weinstein monofilaments, we examined the adaptations of precision g...
Though self-paced walking is highly stereotyped, the stride interval fluctuates from one stride to the next around an average value with a measurable statistical variability. In clinical gait analysis, this variability is usually assessed with indices such the standard deviation or the coefficient of variation (CV). The aim of this study is to unde...
Natural human movements are stereotyped. They minimise cost functions that include energy, a natural candidate from mechanical and physiological points of view. In time-changing environments, however, motor strategies are modified since energy is no longer conserved. Adiabatic invariants are relevant observables in such cases, although they have no...
Natural human movements are stereotyped. They minimise cost functions that include energy, a natural candidate from mechanical and physiological points of view. In time-changing environments, however, motor strategies are modified since energy is no longer conserved. Adiabatic invariants are relevant observables in such cases, although they have no...
Movements rely on a mixture of predictive and reactive mechanisms. With experience, the brain builds internal representations of actions in different contexts. Many factors are taken into account in this process among which the immutable presence of gravity. Any displacement of a massive body in the gravitational field generates forces and torques...
Purpose
The body behaves as a global system with many interconnected subsystems. While the effects of a gravitational change on body responses have been extensively studied in isolation, we are not aware of any study that has examined these two types of body responses concurrently. Here, we examined how the cognitive and cardiovascular systems resp...
Successful completion of natural motor actions relies on feedback information delivered through different modalities, including vision and audition. The nervous system weights these sensory inflows according to the context and they contribute to the calibration and maintenance of internal models. Surprisingly, the influence of auditory feedback on...
Multisensory integration is essential for maintenance of motor and cognitive abilities, thereby ensuring normal function and personal autonomy. Balance control is challenged during senescence or in motor disorders, leading to potential falls. Increased uncertainty in sensory signals is caused by a number of factors including noise, defined as a ran...
The status of classical stability in higher-derivative systems is still subject to discussions. In this note, we argue that, contrary to general belief, many higher-derivative systems are classically stable. The main tool to see this property are Nekhoroshev’s estimates relying on the action-angle formulation of classical mechanics. The latter form...
The status of classical stability in higher-derivative systems is still subject to discussions. In this note, we argue that, contrary to general belief, many higher-derivative systems are classically stable. The main tool to see this property are Nekhoroshev's estimates relying on the action-angle formulation of classical mechanics. The latter form...
Prism adaptation is a well-known model to study sensorimotor adaptive processes. It has been shown that following prism exposure, after-effects are not only restricted to the sensorimotor level but extend as well to spatial cognition. The main purpose of the present study was to investigate in healthy individuals whether expansion to spatial cognit...
The body behaves as a global system with many interconnected subsystems. While the effects of a gravitational change on body responses have been extensively studied in isolation, we are not aware of any study that examined two types of body responses concurrently. Here, we examined how the neurocognitive and cardiovascular systems interact in this...
Switched systems are common in artificial control systems. Here, we suggest that the brain adopts a switched feedforward control of grip forces during manipulation of objects. We measured how participants modulated grip force when interacting with soft and rigid virtual objects when stiffness varied continuously between trials. We identified a sudd...
Humans have a remarkable ability to adjust the way they manipulate tools through a genuine regulation of grip force according to the task. However, rapid changes in the dynamical context may challenge this skill, as shown in many experimental approaches. Most experiments adopt perturbation paradigms that affect only one sensory modality. We hypothe...
Prism adaptation is a well-known model to study sensorimotor adaptive processes. It has been shown that following prism exposure, after-effects are not only restricted to the sensorimotor level but extend as well into spatial cognition. The main purpose of the present study was to investigate in healthy individuals whether expansion to spatial cogn...
Switching systems are common in artificial control systems. Here, we suggest that the brain adopts a switched feedforward control of grip forces during manipulation of objects. We measured how participants modulated grip force when interacting with soft and rigid virtual springs when stiffness varied nearly continuously between trials. We identifie...
Locomotion is a natural task that has been assessed for decades and used as a proxy to highlight impairments of various origins. So far, most studies adopted classical linear analyses of spatio-temporal gait parameters. Here, we use more advanced, yet not less practical, non-linear techniques to analyse gait time series of healthy subjects. We aime...
One remarkable capacity when we grasp and manipulate tools relies on the ability to predict the grip force required to handle them in relation to their mechanical properties and the surrounding environment. However, rapid changes in the dynamical context may constitute a substantial challenge. Here, we test how participants can switch between diffe...
Whether the central nervous system is capable to switch between contexts critically depends on experimental details. Motor control studies regularly adopt robotic devices to perturb the dynamics of a certain task. Other approaches investigate motor control by altering the gravitoinertial context itself as in parabolic flights and human centrifuges....
Background: It is still unknown if physiological complexity and autocorrelations (AC) of long-range stride interval (SI) time series are related to walking direction (WD) and application of galvanic vestibular stimulation (GVS). Methods and results: The SI fluctuations versus time for 34 healthy people walking 15 minutes on an instrumented treadmil...
Introduction The THESEUS project (Towards Human Exploration of Space: a EUropean Strategy) was initiated within the seventh Framework Programme by the European Commission.
The THESEUS project (Towards Human Exploration of Space: a European Strategy), initiated within the seventh Framework Programme by the European Commission, aimed at providing a cross-cutting, life-science-based roadmap for Europe’s strategy towards human exploration of long space missions, and its relevance to applications on Earth. This topic was...
Non–luminance-mediated changes in pupil diameter have been used since the first studies by Darwin in 1872 as indicators of clinical, cognitive, and arousal states. However, the relation between processes involved in motor control and changes in pupil diameter remains largely unknown. Twenty participants attempted to compensate random walks of a cur...
To elaborate a motor plan and perform online control in the gravity field, the brain relies on priors and multisensory integration of information. In particular, afferent and efferent inputs related to the initial state are thought to convey sensorimotor information to plan the upcoming action. Yet, it is still unclear to what extent these cues imp...
The planning of any motor action requires a complex multisensory processing by the brain. Gravity - immutable on Earth - has been shown to be a key input to these mechanisms. Seminal fMRI studies performed during visual perception of falling objects and self-motion demonstrated that humans represent the action of gravity in parts of the cortical ve...
In everyday life, one of the most frequent activities involves accelerating and decelerating an object held in precision grip. In many contexts, humans scale and synchronize their grip force (GF), normal to the finger/object contact, in anticipation of the expected tangential load force (LF), resulting from the combination of the gravitational and...
Skilled tool use and object manipulation critically relies on the ability to scale anticipatorily the grip force (GF) in relation to object dynamics. This predictive behaviour entails that the nervous system is able to store, and then select, the appropriate internal representation of common object dynamics, allowing GF to be applied in parallel wi...
To produce skilled movements, the brain flexibly adapts to different task requirements and movement contexts. Two core abilities underlie this flexibility. First, depending on the task, the motor system must rapidly switch the way it produces motor commands and how it corrects movements online, i.e. it switches between different (feedback) control...
Mental imagery is a cognitive tool that helps humans take decisions by simulating past and future events. The hypothesis has been advanced that there is a functional equivalence between actual and mental movements. Yet, we do not know whether there are any limitations to its validity even in terms of some fundamental features of actual movements, s...
Most object manipulation tasks involve a series of actions demarcated by mechanical contact events, and gaze is usually directed to the locations of these events as the task unfolds. Typically, gaze foveates the target 200 ms in advance of the contact. This strategy improves manual accuracy through visual feedback and the use of gaze-related signal...
To produce skilled movements, the brain flexibly adapts to different task requirements and movement contexts. Two core abilities underlie this flexibility. First, depending on the task, the motor system must rapidly switch the way it produces motor commands and how it corrects movements online, i.e. it switches between different (feedback) control...
Knee injuries are common in sport competitions. Risks of injuries can be significantly lowered by warm-up exercise prior to intense activity. This study aimed to determine simultaneously the long-term effect of competitive volleyball training and short-term effect of a warm-up exercise on passive kinematics and musculo-articular impedance of the kn...
Anticipatory grip force adjustments are a prime example of the predictive nature of motor control. An object held in precision grip is stabilized by fine adjustments of the grip force against changes in tangential load force arising from inertia during acceleration and deceleration. When an object is subject to sudden impact loads, prediction becom...
Redundancy is a fundamental feature of biological motor systems. For example, when touching an object, many different combinations of movements of the shoulder, elbow, wrist, and finger joints result in the same movement at the fingertip. Exploiting this redundancy, the motor system distributes work across effectors to minimize signal-dependent noi...
Human motor behavior is constantly adapted through the process of error-based learning. When the motor system encounters an error, its estimate about the body and environment will change, and the next movement will be immediately modified to counteract the underlying perturbation. Here, we show that a second mechanism, use-dependent learning, simul...
Fine prehension is ubiquitous in everyday skilled hand manipulations. The anticipatory nature of the control of normal grip forces exerted against tangential loads has been extensively used to provide insights into the working of neural control of movements. We designed a new versatile device to measure the three dimensional forces and torques duri...
In many nonprimate species, rhythmic patterns of activity such as locomotion or respiration are generated by neural networks at the spinal level. These neural networks are called central pattern generators (CPGs). Under normal gravitational conditions, the energy efficiency and the robustness of human rhythmic movements are due to the ability of CP...
Object manipulation requires rapid increase in grip force to prevent slippage when the load force of the object suddenly increases. Previous experiments have shown that grip force reactions interact between the hands when holding a single object. Here we test whether this interaction is modulated by the object dynamics experienced before the pertur...
A new study shows that the nervous system has the flexibility to learn dynamics in object-centered coordinates - up to a limit.
Given the high relevance of visual input to human behavior, it is often important to precisely monitor the spatial orientation of the visual axis. One popular and accurate technique for measuring gaze orientation is based on the dual search coil. This technique does not allow for very large displacements of the subject, however, and is not robust w...
In this experiment we examined the coupling between grip force and load force observed during cyclic vertical arm movements with a hand-held object, performed in different gravitational environments. Six subjects highly experienced in parabolic flight participated in this study. They had to continuously move a cylindrical object up and down in the...
A research team has designed a series of experiments to study the effects of a change in gravity on the dynamics of prehension, on the kinematics of upper limb movements and on eye-hand coordination. The anticipatory grip force used to support the object would need to be modified, in a modified gravitational environment. An experiment was performed...
The objective of this study was to measure the forces applied on an object manipulated in different gravitational fields attained during parabolic flights. Eight subjects participated flights (ES) and four were inexperienced (NES). They had to move continuously an instrumented object up and down in three different gravitational conditions (1 g, 1.8...
Questions
Questions (3)
In the motor control field in the broad sense, there are apparently different concepts that seem actually similar to me. What are the differences between motor adaptation, model-free learning, model-based learning, implicit learning, explicit learning? The best ones - and most cryptic to me - come from the prism adaptation field: "recalibration" and "realignment"? These two are simply different ways to say the same thing, i.e, motor adaptation that occurs over trials and a more cognitive strategy (model-based) that allow the system to have a good "first guess". Any reaction to this? Even philosophically ;-)
Hi folks,
This is an obvious question but I was wondering whether anyone knows a study which compares the rate of adaptation to force fields or visuomotor rotation in reaching in function of number of targets? A rule of thumb is to add more than one target in order to be able to reliably measure adaptation rate.
Thanks!
Force field learning paradigms often start with baseline, unperturbed trials when a subject holds on a robotic device and does reaching movements. Then, in a block of trials, the robot applies a perturbation, e.g. a force field that deviates the hand trajectory sideways and proportional to the reaching velocity. Initial errors are made and gradually disappear. In that phase, we can estimate learning rate. Finally, in a last set of trials, the robot is passive and the subject still expects a force field. Since there is none, he makes errors in the other direction before converging back to a normal, error-free behaviour. In that last phase, we can measure the washout phase.
My basic question is: does a subject who learns slowly also forgets slowly? Is there any published work related to that question?
Thanks !!
