Neural bases of hand synergies

abstract: The human hand has so many degrees of freedom that it may seem impossible to control. A potential solution to this problem is “synergy control” which combines dimensionality reduction with great flexibility. With applicability to a wide range of tasks, this has become a very popular concept. In this review, we describe the evolution of the modern concept using studies of kinematic and force synergies in human hand control, neurophysiology of cortical and spinal neurons, and electromyographic (EMG) activity of hand muscles. We go beyond the often purely descriptive usage of synergy by reviewing the organization of the underlying neuronal circuitry in order to propose mechanistic explanations for various observed synergy phenomena. Finally, we propose a theoretical framework to reconcile important and still debated concepts such as the definitions of “fixed” vs. “flexible” synergies and mechanisms underlying the combination of synergies for hand control.View the article as published at http://journal.frontiersin.org/article/10.3389/fncom.2013.00023/ful

Neural bases of hand synergies

The human hand has so many degrees of freedom that it may seem impossible to control. A potential solution to this problem is "synergy control" which combines dimensionality reduction with great flexibility. With applicability to a wide range of tasks, this has become a very popular concept. In this review, we describe the evolution of the modern concept using studies of kinematic and force synergies in human hand control, neurophysiology of cortical and spinal neurons, and electromyographic (EMG) activity of hand muscles. We go beyond the often purely descriptive usage of synergy by reviewing the organization of the underlying neuronal circuitry in order to propose mechanistic explanations for various observed synergy phenomena. Finally, we propose a theoretical framework to reconcile important and still debated concepts such as the definitions of "fixed" vs. "flexible" synergies and mechanisms underlying the combination of synergies for hand control

An experimental analysis regarding neural bases of hand synergies during reach-to-grasp movements

Traumatic brain injury and diseases causing cortical damage is a global problem. Despite their vast extent, their pathophysiology is poorly understood. It is however known that the loss of motor functions can be regained thanks to adaptive properties of the neuronal system. Early task specific motor training is proven to be critical for rehabilitation. We set out to better understand how the CNS controls hand movement to in the future be able to access optimal diagnosis and motor training succeeding cortical damage. The approach, being to reach experimental support to the theory that muscle synergies during reach-to-grasp type movements are mirrored by synergies in cortical activity, was put into effect with the use of a tracking device for hand movement called Leap Motion, and an EEG system. Simultaneous recordings from these two systems were made on subjects to document angles of the hand as well as EEG signals in the cortex during approximately 100 repeats of four different types of carefully designed reach-to-grasp movements. Correlations between specific angles of the hand during the movements were calculated and plotted, as well as correlations between all electrodes. PCA was performed on both data sets to evaluate the possibility of dimensionality reduction. The results revealed groups with similar correlation patterns in both angular and EEG data, as well as primary principal components with high eigenvalues for both data sets, supporting the documented notion of muscular synergies as well as the theory of synergistic behaviour in the CNS.Få grepp om hjärnan Området i hjärnan som styr händerna och uppfattar känsel i dem är väldigt stort jämfört med andra områden. Skador i den delen av hjärnan, som kan bero på sjukdomar eller olyckor, orsakar ofta problem med att utföra vardagliga handrörelser. Problemen kan minska mycket med hjälp av specifik rörelseträning, men vi vet än idag inte hur vi på bästa sätt ska utforma rörelseträningen för varje person för att hen ska få tillbaka sin rörelseförmåga. Vårt arbete har riktat in sig på att ge en bättre förståelse för hur hjärnan styr handrörelser, huvudsakligen när vi greppar tag i saker. Att förstå hur det fungerar hade bland annat öppnat dörrar till nya hjälpmedel vid hjärnskador, och kunnat ge framsteg inom skapandet av robotproteser. Därför har vi noga studerat handrörelser i vårt arbete. Det har vi gjort med hjälp av två olika system: en rörelsesensor och ett system som läser hjärnsignaler. Rörelsesensorn kopplar man in i datorn, och den känner i sin tur av handrörelser och speglar dem på datorskärmen. Hjärnsignalerna har vi läst av med ett system som kallas för EEG. Tillsammans med rörelsesensorn och EEG-systemet har vi gjort mätningar på folk medan de greppat olika saker som används i vargaden. Sedan har vi tittat på den insamlade datan för att bättre förstå både handrörelserna i sig, och hjärnans roll i det hela. Genom att överblicka och göra beräkningar på datan har vi sett att det finns en möjlighet att olika delar av hjärnan samarbetar på ett sätt vid handrörelser som man inte sett eller bevisat tidigare. Att med säkerhet kunna bevisa det hade krävt mer arbete. Därför kommer avdelningen som vi har gjort arbetet på att fortsätta med arbetet. Du är varmt välkommen att läsa vår rapport om du tycker detta verkar intressant

Intuitive Hand Teleoperation by Novice Operators Using a Continuous Teleoperation Subspace

Human-in-the-loop manipulation is useful in when autonomous grasping is not able to deal sufficiently well with corner cases or cannot operate fast enough. Using the teleoperator's hand as an input device can provide an intuitive control method but requires mapping between pose spaces which may not be similar. We propose a low-dimensional and continuous teleoperation subspace which can be used as an intermediary for mapping between different hand pose spaces. We present an algorithm to project between pose space and teleoperation subspace. We use a non-anthropomorphic robot to experimentally prove that it is possible for teleoperation subspaces to effectively and intuitively enable teleoperation. In experiments, novice users completed pick and place tasks significantly faster using teleoperation subspace mapping than they did using state of the art teleoperation methods.Comment: ICRA 2018, 7 pages, 7 figures, 2 table

Neural Models of Temporally Organized Behaviors: Handwriting Production and Working Memory

Advanced Research Projects Agency (ONR N00014-92-J-4015); Office of Naval Research (N00014-91-J-4100, N00014-92-J-1309

On Neuromechanical Approaches for the Study of Biological Grasp and Manipulation

Biological and robotic grasp and manipulation are undeniably similar at the level of mechanical task performance. However, their underlying fundamental biological vs. engineering mechanisms are, by definition, dramatically different and can even be antithetical. Even our approach to each is diametrically opposite: inductive science for the study of biological systems vs. engineering synthesis for the design and construction of robotic systems. The past 20 years have seen several conceptual advances in both fields and the quest to unify them. Chief among them is the reluctant recognition that their underlying fundamental mechanisms may actually share limited common ground, while exhibiting many fundamental differences. This recognition is particularly liberating because it allows us to resolve and move beyond multiple paradoxes and contradictions that arose from the initial reasonable assumption of a large common ground. Here, we begin by introducing the perspective of neuromechanics, which emphasizes that real-world behavior emerges from the intimate interactions among the physical structure of the system, the mechanical requirements of a task, the feasible neural control actions to produce it, and the ability of the neuromuscular system to adapt through interactions with the environment. This allows us to articulate a succinct overview of a few salient conceptual paradoxes and contradictions regarding under-determined vs. over-determined mechanics, under- vs. over-actuated control, prescribed vs. emergent function, learning vs. implementation vs. adaptation, prescriptive vs. descriptive synergies, and optimal vs. habitual performance. We conclude by presenting open questions and suggesting directions for future research. We hope this frank assessment of the state-of-the-art will encourage and guide these communities to continue to interact and make progress in these important areas

A review and consideration on the kinematics of reach-to-grasp movements in macaque monkeys

The bases for understanding the neuronal mechanisms that underlie the control of reach-to-grasp movements among nonhuman primates, particularly macaques, has been widely studied. However, only a few kinematic descriptions of their prehensile actions are available. A thorough understanding of macaques' prehensile movements is manifestly critical, in light of their role in biomedical research as valuable models for studying neuromotor disorders and brain mechanisms, as well as for developing brain-machine interfaces to facilitate arm control. This article aims to review the current state of knowledge on the kinematics of grasping movements that macaques perform in naturalistic, semi-naturalistic, and laboratory settings, to answer the following questions: Are kinematic signatures affected by the context within which the movement is performed? In what ways is kinematics of humans' and macaques' prehensile actions similar/dissimilar? Our analysis reflects the challenges involved in making comparisons across settings and species due to the heterogeneous picture in terms of the number of subjects, stimuli, conditions, and hands used. The kinematics of free-ranging macaques are characterized by distinctive features that are exhibited neither by macaques in laboratory setting nor human subjects. The temporal incidence of key kinematic landmarks diverges significantly between species, indicating disparities in the overall organization of movement. Given such complexities, we attempt a synthesis of extant body of evidence, intending to generate some significant implications for directions that future research might take, to recognize the remaining gaps and pursue the insights and resolutions to generate an interpretation of movement kinematics that accounts for all settings and subjects

Making tools and making sense: complex, intentional behaviour in human evolution

Stone tool-making is an ancient and prototypically human skill characterized by multiple levels of intentional organization. In a formal sense, it displays surprising similarities to the multi-level organization of human language. Recent functional brain imaging studies of stone tool-making similarly demonstrate overlap with neural circuits involved in language processing. These observations consistent with the hypothesis that language and tool-making share key requirements for the construction of hierarchically structured action sequences and evolved together in a mutually reinforcing way