David W Franklin

David W Franklin
Technische Universität München | TUM · Faculty of Sport and Health Science

Ph.D.

About

112
Publications
17,507
Reads
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6,208
Citations
Introduction
Our research examines how humans learn models of the external world and use these to adapt our movements to new experiences. A major focus of this research is how we adapt to instability in the environment through co-activation of our muscles to control the endpoint stiffness of our limbs. By investigating changes in trajectories, endpoint stiffness, and electrical activity of the muscles, we hope to elucidate the underlying mechanisms by which the brain learns new tasks.
Additional affiliations
January 2007 - January 2016
University of Cambridge
Position
  • Research Associate
December 1999 - December 2006

Publications

Publications (112)
Conference Paper
Object manipulation often requires coordination between hands and adaption to the dynamic characteristics of the object. When manipulating the same object, the two hands can have either symmetric or asymmetric impacts on the object's trajectory. In this work, we used a bimanual manipulation task of a complex object with internal dynamics to examine...
Conference Paper
During object manipulation, our sensorimotor sys-tem needs to represent the objects dynamics in order to better control it. This is especially important in the case of grip force control where small forces can cause the object to slip from our fingers, and excessive forces can cause fatigue or even damage the object. While the tradeoff between thes...
Conference Paper
Humans have unrivaled abilities to perform dexterous object manipulation. This requires the sensorimotor system to quickly adapt to environmental changes and predictively counteract external disturbances. Many studies have focused on the anticipatory control of digits with real-world experiments. However, examining manipulation using virtual realit...
Conference Paper
When grasping and manipulating objects we implicitly adapt grip forces according to the physical parameters of the object. We integrate visual, cutaneous, and force feedback to estimate these parameters and adapt our control accordingly. Using virtual reality, both feedback integration and control can be investigated in ways that are not possible u...
Article
The separation of distinct motor memories by contextual cues is a well known and well studied phenomenon of feedforward human motor control. However, there is no clear evidence of such context-induced separation in feedback control. Here we test both experimentally and computationally if context-dependent switching of feedback controllers is possib...
Preprint
Full-text available
Intuitive and efficient physical human-robot collaboration relies on the mutual observability of the human and the robot, i.e. the two entities being able to interpret each other's intentions and actions. This is remedied by a myriad of methods involving human sensing or intention decoding, as well as human-robot turn-taking and sequential task pla...
Article
Full-text available
Learning new movement patterns is a normal part of daily life, but of critical importance in both sport and rehabilitation. A major question is how different sensory signals are integrated together to give rise to motor adaptation and learning. More specifically, there is growing evidence that pain can give rise to alterations in the learning proce...
Article
Full-text available
The cross-industry concept of Digital Twin promises numerous benefits in areas such as product customization and predictive maintenance, but many companies often struggle to determine a starting point. Digital Twin use cases are abundant, but efforts and stakeholder benefits are difficult to estimate when developing and implementing Digital Twin ap...
Article
Full-text available
The Digital Twin concept promises numerous applications across industries and its physical twin’s entire life cycle. Although numerous architectures have been proposed to develop and describe the setup of Digital Twin applications, current Digital Twin architectures do not address the versatile cross-industry character of the Digital Twin concept,...
Preprint
Full-text available
The separation of distinct motor memories by contextual cues is a well known and well studied phenomenon of feedforward human motor control. However, there is no clear evidence of such context-induced separation in feedback control. Here we test both experimentally and computationally if context-dependent switching of feedback controllers is possib...
Article
Full-text available
The perception of our body in space is flexible and manipulable. The predictive brain hypothesis explains this malleability as a consequence of the interplay between incoming sensory information and our body expectations. However, given the interaction between perception and action, we might also expect that actions would arise due to prediction er...
Article
Full-text available
Computational optimal feedback control (OFC) models in the sensorimotor control literature span a vast range of different implementations. Among the popular algorithms, finite-horizon, receding-horizon or infinite-horizon linear-quadratic regulators (LQR) have been broadly used to model human reaching movements. While these different implementation...
Article
Full-text available
A Digital Twin is an auspicious cross-industry concept in the era of digitalization, which promises a wide range of benefits such as efficiency improvements, predictions of future opportunities and challenges, and respective recommendations. At present, a variety of definitions and terms exist, causing increasing confusion among practitioners and u...
Article
Full-text available
Switching between motor tasks requires accurate adjustments for changes in dynamics (grasping a cup) or sensorimotor transformations (moving a computer mouse). Dual-adaptation studies have investigated how learning of context-dependent dynamics or transformations is enabled by sensory cues. However, certain cues, such as color, have shown mixed res...
Preprint
Learning new movement patterns is a normal part of daily life, but of critical importance in both sport and rehabilitation. A major question is how different sensory signals are integrated together to give rise to motor adaptation and learning. More specifically, there is growing evidence that pain can give rise to alterations in the learning proce...
Poster
Full-text available
In this study, we investigate whether a ball throwing intervention can induce differences in muscle activation, volume and dynamic ranges in piano playing.
Preprint
Full-text available
Computational optimal feedback control (OFC) models in the sensorimotor control literature span a vast range of different implementations. Among the popular algorithms, finite-horizon, receding-horizon or infinite-horizon linear-quadratic regulators (LQR) have been broadly used to model human reaching movements. While these different implementation...
Preprint
Full-text available
Switching between motor tasks requires accurate adjustments for changes in dynamics (grasping a cup) or sensorimotor transformations (moving a computer mouse). Dual-adaptation studies have investigated how learning of context-dependent dynamics or transformations is enabled by sensory cues. However, certain cues, such as color, have shown mixed res...
Preprint
Full-text available
Skillful and accurate object manipulation requires the object's dynamics to be represented within a motor memory. Despite extensive research, how the motor system represents novel dynamics is still an open question. This representation is normally examined by testing the spatial generalization of the learned forces. However, previous studies have n...
Article
A soft touch Measuring the force it takes for a hand to grasp an object requires sensors to be placed on the fingertips, but these sensors will interfere with or affect how much force ends up being applied. Lee et al. developed a nanomesh sensor built from a series of electrospun materials (see the Perspective by Liu). Using a robotic tester, they...
Preprint
Full-text available
A sudden change in dynamics produces large errors leading to increases in muscle co-contraction and feedback gains during early adaptation. We previously proposed that internal model uncertainty drives these changes, whereby the sensorimotor system reacts to the change in dynamics by upregulating stiffness and feedback gains to reduce the effect of...
Preprint
Full-text available
The perception of our body in space is flexible and manipulable. The predictive brain hypothesis explains this malleability as a consequence of the interplay between incoming sensory information and our body expectations. However, given the interaction between perception and action, we might also expect that actions would arise due to prediction er...
Article
Full-text available
Visuomotor feedback responses vary in intensity throughout a reach, commonly explained by optimal control. Here we show that the optimal control for a range of movements with the same goal can be simplified to a time-to-target dependent control scheme. We measure our human participants' visuomotor responses in five reaching conditions, each with di...
Article
Full-text available
In our daily life we often make complex actions comprised of linked movements, such as reaching for a cup of coffee and bringing it to our mouth to drink. Recent work has highlighted the role of such linked movements in the formation of independent motor memories, affecting the learning rate and ability to learn opposing force fields. In these stud...
Preprint
Full-text available
The timescales of adaptation to novel dynamics are well explained by a dual-rate model with slow and fast states. This model can predict interference, savings and spontaneous recovery, but cannot account for adaptation to multiple tasks, as each new task drives unlearning of the previously learned task. Nevertheless, in the presence of appropriate...
Conference Paper
We recently developed a simulated inverted pendulum in order to examine human sensorimotor control strategies for stabilization. This simulated system allows us to manipulate the visual and haptic feedback independently from the physical dynamics of the task. Here we examine the effect of sensory delay in a balancing task. Human participants attemp...
Conference Paper
In this study we experimentally test and model the control behavior of human participants when controlling inverted pendulums of different dynamic lengths, and with visual feedback of varying congruence to these dynamic lengths. Participants were asked to stabilize the inverted pendulum of L = 1 m and L = 4 m, with visual feedback shown at various...
Conference Paper
We developed a new technique to measure the contributions of rapid visuomotor feedback responses to the stabilization of a simulated inverted pendulum. Human participants balanced an inverted pendulum simulated on a robotic manipulandum. At a random time during the balancing task, the visual representation of the tip of the pendulum was shifted by...
Conference Paper
Full-text available
Successful manipulation of objects requires forming internal representations of the object dynamics. To do so, the sensorimotor system uses visual feedback of the object movement allowing us to estimate the object state and build the representation. One way to investigate this mechanism is by introducing a discrepancy between the visual feedback ab...
Preprint
Full-text available
In our daily life we often make complex actions comprised of linked movements, such as reaching for a cup of coffee and bringing it to our mouth to drink. Recent work has highlighted the role of such linked movements in the formation of independent motor memories, affecting the learning rate and ability to learn opposing force fields. However, whil...
Preprint
Full-text available
Visuomotor feedback gains vary in magnitude throughout a reach, commonly explained by optimal control. However, this pattern also matches the hand velocity profile, suggesting a simpler, perhaps hardwired, controller. Here we test between these alternatives, examining whether movement velocity regulates visuomotor gains. Feedback gain profiles were...
Chapter
No single muscle model exists that has the same mechanical impedance and force development properties as biological muscle. It is essential to develop a muscle model with the same force limitations and impedance as biological muscle, especially for predictive simulations, as these properties are taken into account when choosing a posture for a spec...
Chapter
Prior work has shown that independent motor memories of opposing dynamics can be learned when the movements are preceded by unique lead-in movements, each associated with a different direction of dynamics. Here we examine generalization effects using visual lead-in movements. Specifically, we test how variations in lead-in kinematics, in terms of d...
Article
Full-text available
During reaching movements in the presence of novel dynamics, participants initially co-contract their muscles to reduce kinematic errors and improve task performance. As learning proceeds, muscle co-contraction decreases as an accurate internal model develops. The initial co-contraction could affect the learning of the internal model in several way...
Conference Paper
Sensorimotor control regulates balance and stability as well as adaptation to the external environment. We introduce the use of a simulated inverted pendulum to study human sensorimotor control, demonstrating that this system introduces similar control challenges to human subjects as a physical inverted pendulum. Participants exhibited longer stabi...
Article
Full-text available
Adaptation to novel dynamics requires learning a motor memory, or a new pattern of predictive feedforward motor commands. Recently we demonstrated the up-regulation of rapid visuomotor feedback gains early in curl force field learning, which decrease once a predictive motor memory is learned. However, even after learning is complete, these feedback...
Article
Full-text available
Rapid learning can be critical to ensure elite performance in a changing world or to recover basic movement after neural injuries. Recently it was shown that the variability of follow-through movements affects the rate of motor memory formation. Here we investigate if lead-in movement has a similar effect on learning rate. We hypothesized that both...
Article
Full-text available
Movement planning is thought to be primarily determined by motor costs such as inaccuracy and effort. Solving for the optimal plan that minimizes these costs typically leads to specifying a time-varying feedback controller which both generates the movement and can optimally correct for errors that arise within a movement. However, the quality of th...
Data
This supplementary material includes: 1) Full details of the derivation with the resultant update rules for the optimal controller and the Kalman gains. 2) Specific properties of the optimal controller for a system with decoupled dynamics. 3) The model of two dimensional arm movement and corresponding parameters used in our simulation. 4) Sensitivi...
Article
Full-text available
Movement planning is thought to be primarily determined by motor costs such as inaccuracy and effort. Solving for the optimal plan that minimizes these costs typically leads to specifying a time-varying feedback controller which both generates the movement and can optimally correct for errors that arise within a movement. However, the quality of th...
Article
Full-text available
Recent theories of limb control emphasize motor cortex as a dynamical system, with planning setting the initial neural state, and execution arising from the self-limiting evolution of the intrinsic neural dynamics. Therefore, movements that share an initial trajectory but then diverge might have different neural states during the execution of the i...
Article
Full-text available
Recent theories of limb control emphasize motor cortex as a dynamical system, with planning setting the initial neural state, and execution arising from the self-limiting evolution of the intrinsic neural dynamics. Therefore, movements that share an initial trajectory but then diverge might have different neural states during the execution of the i...
Article
Full-text available
The coordinate system in which humans learn novel motor skills is controversial. The representation of sensorimotor skills has been extensively studied by examining generalization after learning perturbations specifically designed to be ambiguous as to their coordinate system. Recent studies have found that learning is not represented in any simple...
Article
Full-text available
Visual observation of movement plays a key role in action. For example, tennis players have little time to react to the ball, but still need to prepare the appropriate stroke. Therefore, it might be useful to use visual information about the ball trajectory to recall a specific motor memory. Past visual observation of movement (as well as passive a...
Article
Full-text available
Goal-directed reaching movements are guided by visual feedback from both target and hand. The classical view is that the brain extracts information about target and hand positions from a visual scene, calculates a difference vector between them, and uses this estimate to control the movement. Here we show that during fast feedback control, this com...
Conference Paper
Full-text available
The human sensorimotor control system generates movement by adapting and controlling the mechanics of the musculoskeletal system. To generate skilful movements the sensorimotor control system must be able to predict and compensate for any disturbances generated either in our own body or in the external environment. While stable and repeatable pertu...
Article
Full-text available
In sports, the role of backswing is considered critical for generating a good shot, even though it plays no direct role in hitting the ball. We recently demonstrated the scientific basis of this phenomenon by showing that immediate past movement affects the learning and recall of motor memories. This effect occurred regardless of whether the past c...
Article
Full-text available
When opposing force fields are presented alternately or randomly across trials for identical reaching movements, subjects learn neither force field, a behavior termed 'interference'. Studies have shown that a small difference in the endpoint posture of the limb reduces this interference. However, any difference in the limb's endpoint location typic...
Article
Full-text available
In ball sports, we are taught to follow through, despite the inability of events after contact or release to influence the outcome [1, 2]. Here we show that the specific motor memory active at any given moment critically depends on the move-ment that will be made in the near future. We demonstrate that associating a different follow-through movemen...
Article
Full-text available
No abstract available for this article.
Article
Full-text available
Recent studies have highlighted the modulation and control of feedback gains as support for optimal feedback control. While many experiments contrast feedback gains across different environments, only a few have demonstrated the appropriate modulation of feedback gains from one movement to the next. Here we extend previous work by examining whether...
Article
Full-text available
After committing to an action, a decision-maker can change their mind to revise the action. Such changes of mind can even occur when the stream of information that led to the action is curtailed at movement onset. This is explained by the time delays in sensory processing and motor planning which lead to a component at the end of the sensory stream...
Article
Full-text available
The human motor system is remarkably proficient in the online control of visually guided movements, adjusting to changes in the visual scene within 100 ms [1-3]. This is achieved through a set of highly automatic processes [4] translating visual information into representations suitable for motor control [5, 6]. For this to be accomplished, visual...
Article
Full-text available
Successful motor performance requires the ability to adapt motor commands to task dynamics. A central question in movement neuroscience is how these dynamics are represented. Although it is widely assumed that dynamics (e.g. force-fields) are represented in intrinsic, joint-based coordinates (Shadmehr and Mussa-Ivaldi 1994), recent evidence has que...
Article
Full-text available
Impedance control can be used to stabilize the limb against both instability and unpredictable perturbations. Limb posture influences motor noise, energy usage and limb impedance as well as their interaction. Here we examine whether subjects use limb posture as part of a mechanism to regulate limb stability. Subjects performed stabilization tasks w...
Article
Full-text available
Recent theoretical frameworks such as optimal feedback control suggest that feedback gains should modulate throughout a movement and be tuned to task demands. Here we measured the visuomotor feedback gain throughout the course of movements made to "near" or "far" targets in human subjects. The visuomotor gain showed a systematic modulation over the...
Article
Full-text available
Several studies have shown that sensory contextual cues can reduce the interference observed during learning opposing force fields. However, as each study examined a small set of cues often in a unique paradigm, the relative efficacy of different sensory contextual cues is unclear. Here we quantify how seven contextual cues, some investigated previ...
Article
Full-text available
Humans skillfully manipulate objects and tools despite the inherent instability. In order to succeed at these tasks, the sensorimotor control system must build an internal representation of both the force and mechanical impedance. As it is not practical to either learn or store motor commands for every possible future action, the sensorimotor contr...