Humans Use Similar Posture Sequences in a Whole-Body Tracing Task

2020

Preprint

Self Cite

Humans have elegant bodies that allow gymnastics, piano playing, and tool use, but understanding how they do this in detail is difficult because their musculoskeletal systems are extraordinarily complicated. Nonetheless, although movements can be very individuated, some common movements like walking and reaching can be stereotypical, with the movement cost a major factor. A recent study has extended these observations by showing that in an arbitrary set of whole-body movements used to trace large-scale closed curves, near-identical posture changes were chosen across different subjects, both in the average trajectories of the body’s limbs and in variations within trajectories. The commonality of that result motivates explanations for this generality. One could be that humans also choose trajectories that are economical in energetic cost. To test this hypothesis, we situate the tracing data within a fifty degree of freedom dynamic model of the human skeleton that allows the computation of movement cost. Comparing the model movement cost data from nominal tracings against various perturbed tracings shows that the latter are more energetically expensive, inferring that the original traces were chosen on the basis of minimum cost. Moreover, the computational approach used to establish minimum cost principle suggests a refinement of what is known about cortical movement representations.Author SummaryAlthough motor cortical areas have been extensively studied, their basic response properties are still only partially understood, and it remains controversial whether neural activity relates to muscle commands or to abstract movement features. We provide a new perspective of how movements may be resented in the brain by showing that humans chose trajectories with minimum energy cost while accomplishing goal-directed tasks. Furthermore, most of the current neural control studies are experimental. Our computational methodology coupled with a minimum energy principle suggests a refinement of the brain’s storage of remembered movements.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Humans use minimum cost movements in a whole-body task

2020

Preprint

Self Cite

“…Once we have vetted the system in many such areas, it can be used as a predictive tool, as in the experiment showing the different costs of reaching targets. We have developed a large-scale three-dimensional tracing experiment in virtual reality [33] to elicit natural whole-body movements under common goals. Our future work is to analyze the energetic cost using the HDM.…”

Section: Discussionmentioning

confidence: 99%

“…Fig. 1 shows a frame from a study of the cost of movements used in a virtual tracing experiment [16]. The model interface 4 shown in allows the construction of the human model using the physics engine via a multi-purpose graphical interface for analyzing movement data captured through interaction with the virtual environment.…”

Section: Model Overviewmentioning

confidence: 99%

Computational Modeling: Human Dynamic Model

Cooper

2020

Preprint

Self Cite

Measurements of human activity are useful for studying the neural computations underlying human behavior. Dynamic models of human behavior also support clinical efforts to analyze, rehabilitate, and predict movements. They are used in biomechanics to understand and diagnose motor pathologies, find new motor strategies that decrease the risk of injury, and predict potential problems from a particular procedure. This paper describes a physics-based movement analysis technique for analyzing and simulating bipedal humanoid movements. A 48 degree of freedom dynamic model of humans uses physical simulation software as a tool for synthesizing humanoid movement with sufficient speed and accuracy to allow the analysis and synthesis of real-time interactive applications such as psychophysics experiments using virtual reality or human-in-the-loop teleoperation of a simulated robotic system. The dynamic model is fast and robust while still providing results sufficiently accurate to be used to believably animate a humanoid character, control a simulated system, or estimate internal joint forces used during a movement for creating effort-contingent experimental stimuli. A virtual reality environment developed as part of this research supports controlled experiments for systematically recording human behaviors.

Humans use minimum cost movements in a whole-body task

2021

Sci Rep

Self Cite

Humans have elegant bodies that allow gymnastics, piano playing, and tool use, but understanding how they do this in detail is difficult because their musculoskeletal systems are extraordinarily complicated. Nonetheless, common movements like walking and reaching can be stereotypical, and a very large number of studies have shown their energetic cost to be a major factor. In contrast, one might think that general movements are very individuated and intractable, but our previous study has shown that in an arbitrary set of whole-body movements used to trace large-scale closed curves, near-identical posture sequences were chosen across different subjects, both in the average trajectories of the body’s limbs and in the variance within trajectories. The commonalities in that result motivate explanations for its generality. One explanation could be that humans also choose trajectories that are economical in cost. To test this hypothesis, we situate the tracing data within a forty eight degree of freedom human dynamic model that allows the computation of movement cost. Using the model to compare movement cost data from nominal tracings against various perturbed tracings shows that the latter are more energetically expensive, inferring that the original traces were chosen on the basis of minimum cost.