Human Motor Skills Research Articles

A method to reversibly degrade proprioceptive feedback in research on human motor control

In research on human motor skills, it is often desirable to manipulate proprioceptive feedback in order to determine its contribution towards subjects’ performance. Here we evaluate an easy-to-use, non-invasive method to temporarily reduce proprioceptive responsiveness. Two physiotherapy vibrators contacted the distal end of the subjects’ forearm on the flexor and extensor side; they were either turned off, or they vibrated at 80Hz with an amplitude of 1mm. We found that vibration substantially impaired subjects’ ability to use their hand in an angle matching, a force production and a haptic shape perception task. We also found that vibration strongly attenuated the H-reflex of the ipsilateral M. flexor carpi radialis. These results suggest that agonist–antagonist vibration is a useful method to degrade proprioceptive responsiveness for research on higher motor functions.

Pharmacological Support of Neurorehabilitation

The administration of numerous facilitatory drugs in combination with appropriate physiotherapeutic approaches is reported to facilitate neurorehabilitation. First evidence of the possible beneficial influence of facilitatory drugs in neurorehabilitation arose from studies investigating the pharmacology of learning in healthy humans. Amphetamine, for example, has shown to improve performance of different somatosensory and motor skills. Paired with physical therapy in stroke patients, it also increases the rate and extent of motor recovery and supports treatment of aphasia. Amphetamine is however known as a "dirty drug", because it acts non-specifically by increasing centrally the levels of dopamine, serotonin, and noradrenaline. Thus, first approaches intend to scrutinize the role of more specifically acting pharmacological agents on learning and neurorehabilitation. In this review, focus is placed on two main topics: (i) studies that aimed to investigate the pharmacological basis of motor and sensory skills in healthy humans and (ii) studies investigating whether the same drugs may also support neurorehabilitation. First, different sensorimotor paradigms are discussed, which were introduced to investigate basic influences of facilitatory pharmaceuticals on cortical plasticity. Then, emphasis is placed on the role of these drugs acting to gate synaptic plasticity in neurorehabilitation. It is concluded that further studies in large populations should focus on more specifically acting pharmaceuticals, their side effects and their capacity in supporting different patterns of physical therapy. Keywords: Cortical reorganization, behavior, dopamine, serotonin, noradrenaline, neurorehabilitation

Pharmacology of Motor and Somatosensory Skills in Humans

The pharmacological basis of changes in human behaviour and associated cortical reorganization remains poorly understood. Different paradigms have been introduced to alter motor and somatosensory skills in humans. The underlying changes in synaptic efficacy can be modulated by pharmacological agents acting to gate synaptic plasticity. Non-invasive imaging techniques offer the possibility to assess parallel changes in cortical processing. Cellular studies suggest that there might be only few, but very basic mechanisms that control regulation of synaptic transmission. In particular, the γ-aminobutyric acid (GABA) and the N-methyl-D-aspartic acid (NMDA) receptor, a specific subtype of the glutamatergic receptors, are thought to be crucial in synaptic plasticity. Thus, the application of benzodiazepines facilitating the binding of GABA on GABA(A) receptors, and NMDA receptor blockers, were found to prevent learning and associated cortical reorganization. While there are many approaches to block plastic processes, less is known about drugs, which enhance learning and cortical plasticity. Growing evidence from human studies support the suggestion that learning is subject to amplification by amphetamine. Amphetamine however acts non-specific by increasing centrally the levels of dopamine, serotonin, and noradrenaline. Thus, first approaches that intend to scrutinize the apparently ubiquitous role of only one of these neurotransmitter systems used more specifically acting pharmacological agents. In this review we focus on studies that aimed to investigate the pharmacology of the motor and somatosensory system. First, we introduce standards for testing potential effects of a substance. Then, we focus on biochemical mechanisms of learning, before discussing different motor and somatosensory paradigms which were introduced to elicit changes in cortical excitability or organization in animals and humans. Emphasis is placed on the role of inhibitory and excitatory pharmacological agents acting to gate synaptic plasticity in healthy subjects and patients. It is concluded that future studies that investigate the interaction between artificially modulated receptor activity and specific patterns of behaviour in various neurological disorders may help to improve our understanding of how to support recovery of motor and somatosensory function pharmacologically. Keywords: cortical reorganization, behaviour, dopamine, serotonin, noradrenaline, g-aminobutyric acid, n-methyl-d-aspartic acid

Corticospinal system development depends on motor experience.

Early motor experiences have been shown to be important for the development of motor skills in humans and animals. However, little is known about the role of motor experience in motor system development. In this study, we address the question of whether early motor experience is important in shaping the development of the corticospinal (CS) tract. We prevented limb use by the intramuscular injection of botulinum toxin A into selected forelimb muscles to produce muscle paralysis during the period of development of CS connection specificity, which is between postnatal weeks 3 and 7. CS terminations were examined using an anterograde tracer. Preventing normal forelimb use during CS axon development produced defective development of CS terminations at week 8 and in maturity. There were reductions in the topographic distribution of axon terminals, in terminal and preterminal branching, and in varicosity density. This suggests that limb use is needed to refine CS terminals into topographically specific clusters of dense terminal branches and varicosities. To determine correlated effects on motor behavior, cats were tested in a prehension task, to reach and grasp a piece of food from a narrow food well, when the neuromuscular blockade dissipated (by week 10) and in maturity (week 16). Preventing normal limb use also produced a prehension deficit later in development and in maturity, in which there was a loss of the supination component of grasping. This component of prehension in the cat depends on CS projections from the paw representation of rostral motor cortex to the cervical enlargement. Our findings show that motor experiences are necessary for normal development of CS terminations and function.

Fast force-generation dynamics of human articulatory muscles.

To explore the mechanisms of speech articulation, which is one of the most sophisticated human motor skills controlled by the central nervous system, we investigated the force-generation dynamics of the human speech articulator muscles [orbicularis oris superior (OOS) and inferior (OOI) muscles of the lips]. Short-pulse electrical stimulation (300 micros) with approximately three or four times the sensation threshold intensity of each subject induced the muscle response. The responses of these muscles were modeled as second-order dynamics with a time delay (TD), and the model parameters [natural frequency (NF), damping ratio (DR), and TD] were identified with a nonlinear least mean squares method. The OOS (NF: 6.1 Hz, DR: 0.71, TD: 14.5 ms) and OOI (NF: 6.1 Hz, DR: 0.68, TD: 15.6 ms) showed roughly similar characteristics in eight subjects. The dynamics in the tongue (generated by combined muscles) also showed similar characteristics (NF: 6.1 Hz, DR: 0.68, TD: 17.4 ms) in two subjects. The NF was higher, and the DR was lower than results measured for arm muscles (NF: 4.25 Hz, DR: 1.05, TD: 23.8 ms for triceps long head), indicating that articulatory organs adapt for more rapid movement. In contrast, slower response dynamics was estimated when muscle force data by voluntarily contraction task were used for force-generation dynamics modeling. We discuss methodological problems in estimating muscle dynamics when different kinds of muscle contraction methods are used.

Diurnal variations of subjective symptoms and motor activity in depressed patients

Human motor skills or impairments have been traditionally assessed by neurologists by means of paper-and-pencil tests or special hardware. More recently, technologies such as digitizing tablets and touchscreens have offered neurologists new assessment possibilities, but their use has been restricted to a specific medical condition, or to stylus-operated mobile devices. The objective of this paper is twofold. First, we propose a mobile app (MotorBrain) that offers six computerized versions of traditional motor tests, can be used directly by patients (with and without the supervision of a clinician), and aims at turning millions of smartphones and tablets available to the general public into data collection and assessment tools. Then, we carry out a study to determine whether the data collected by MotorBrain can be meaningful for describing aging in human motor performance.A sample of healthy participants (N = 133) carried out the motor tests using MotorBrain on a smartphone. Participants were split into two groups (Young, Old) based on their age (less than or equal to 30 years, greater than or equal to 50 years, respectively). The data collected by the app characterizes accuracy, reaction times, and speed of movement. It was analyzed to investigate differences between the two groups.The app does allow measuring differences in neuromotor performance. Data collected by the app allowed us to assess performance differences due to the aging of the neuromuscular system.Data collected through MotorBrain is suitable to make meaningful distinctions among different kinds of performance, and allowed us to highlight performance differences associated to aging. MotorBrain supports the building of a large database of neuromotor data, which can be used for normative purposes in clinical use.

Festina lente: evidences for fast and slow learning processes and a role for sleep in human motor skill learning.

Festina lente: evidences for fast and slow learning processes and a role for sleep in human motor skill learning.

Human Motor Skills and the Cerebellum

Human Motor Skills and the Cerebellum

A neurobiological perspective on humanoid robot design

Neurobiology and neuroengineering can offer insights to humanoid robot designers. Motor primitive concepts and mammalian cortex motor coding provide a useful framework for designing learning systems that replicate human motor skills.

Task‐level interaction with virtual environments and virtual actors

In many virtual environment (VE) applications, the VE system must be able to display accurate models of human figures that can perform routine behaviors and adapt to events in the virtual world. In order to achieve such adaptive, task‐level interaction with virtual actors, it is necessary to model elementary human motor skills. SkillBuilder is a software system for constructing a set of motor behaviors for a virtual actor by designing motor programs for arbitrarily complicated skills. Motor programs are modeled using finite state machines, and a set of state machine transition and ending conditions for modeling motor skills has been developed. Using inverse kinematics and automatic collision avoidance, SkillBuilder was used to construct a suite of behaviors for simulating visually guided reaching, grasping, and head‐eye tracking motions for a kinematically simulated actor consisting of articulated, rigid body parts. All of these actions have been successfully demonstrated in real time by permitting the us...

Evidence of a time constant associated with movement patterns in six mammalian species

Human psychophysical studies have provided evidence of a short duration time constant associated with perceptual tasks. This time constant is approximately 3 s in duration, and evidence suggests that it represents a central neural mechanism that functions to integrate “successive events into a Gestalt” in order to create a “subjective present.” Recent studies have found a 3 s time constant in human and chimpanzee movement patterns, suggesting that a similar mechanism subserves both human perceptual and primate motor skills. These studies have focused exclusively on humans and chimpanzees; therefore, it is unclear whether this time constant represents a characteristic derived in the primate order or an ancestral characteristic found in many different mammalian orders. The current study looked for evidence of a 3 s time constant associated with movement patterns in six mammalian species representing three non-primate orders. The results showed that all six species' movement pattern event durations averaged about 3 s, and that there were no significant differences in the mean event durations among the species. Thus, the 3 s time constant originally found in human perceptual and primate motor skills is common among many mammalian orders and probably represents the operation of an ancestral neural mechanism.

Intrasubject Variability of Selected Force-Platform Parameters in the Quantification of Postural Control

Platform stabilometry is increasingly applied to monitor or re-educate standing balance in clinical rehabilitation. Consequently, insight is needed into the validity, reliability, and sensitivity of different force-platform parameters. This study focuses on the intrasubject variability as the major source of variance (unreliability) in the study of human motor skills. The intrasubject variability of several, commonly applied force-platform parameters was determined across ten repeated tests of quiet two-legged standing in healthy subjects to identify the most consistent and stable parameters in the quantification of postural control. The variability of the root mean square (RMS) amplitude, peak-to-peak amplitude, mean frequency, and RMS velocity of the fore-aft and lateral components of the center-of-pressure fluctuations was investigated under varying (visual and cognitive) task conditions. The results indicate that all selected parameters show considerable intrasubject variability irrespective of the task context. Nonetheless, both the RMS amplitude and RMS velocity in either direction of sway do not demonstrate a significant trend across repeated tests. Among the selected parameters, the RMS velocity in the fore-aft direction shows the greatest intrasubject consistency, as well as a high sensitivity to, for example, visual deprivation. These findings support the reliability and validity of this parameter in the clinical quantification of postural control.

Knowledge-based control of grasping in robot hands using heuristics from human motor skills

The development of a grasp planner for multifingered robot hands is described. The planner is knowledge-based, selecting grasp postures by reasoning from symbolic information on target object geometry and the nature of the task. The ability of the planner to utilize task information is based on an attempt to mimic human grasping behavior. Several task attributes and a set of heuristics derived from observation of human motor skills are included in the system. The paper gives several examples of the reasoning of the system in selecting the appropriate grasp mode for spherical and cylindrical objects for different tasks.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Variations in sex-related cognitive abilities across the menstrual cycle

Sex differences in human cognitive and motor skills may in part be due to organizational or activational effects of sex hormones on the brain. In this study, an extensive battery of cognitive and motor tests was administered to normally cycling women at two phases of the menstrual cycle, in order to detect any hormone-mediated changes in performance. Results confirmed changes across the menstrual cycle on a variety of speeded manual and articulatory measures, and on some nonverbal/spatial tests. The results provide qualified support for the hypothesis that the high levels of gonadal steroids present at the luteal phase of the cycle may facilitate skills favoring females, but be detrimental to skills favoring males. The implications of these results for research in the area of human sex differences are discussed.

Integrating neural networks and knowledge-based systems for intelligent robotic control

A methodology is presented for integrating artificial neural networks and knowledge-based systems for the purpose of robotic control. The integration is patterned after models of human motor skill acquisition. The initial control task chosen to demonstrate the integration technique involves teaching a two-link manipulator how to make a specific type of swing. A three-level task hierarchy is defined consisting of low-level reflexes, reflex modulators, and an execution monitor. The rule-based execution monitor first determines how to make a successful swing using rules alone. It then teaches cerebellar model articulation controller (CMAC) neural networks how to accomplish the task by having them observe rule-based task execution. Following initial training, the execution monitor continuously evaluates neural network performance and re-engages swing-maneuver rules whenever changes in the manipulator or its operating environment necessitate retraining of the networks. Simulation results show the interaction between rule-based and network-based system components during various phases of training and supervision.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Reciprocal effects of hormonal fluctuations on human motor and perceptual-spatial skills.

Normal adult women showed systematic performance fluctuations across the menstrual cycle on several motor and perceptual tests that typically yield sex differences in performance. The midluteal phase, characterized by high levels of estradiol and progesterone, was associated with improved performance on tests of speeded motor coordination and impaired performance on a perceptual-spatial test, relative to performance during menses. Variations in gonadal steroid levels may contribute substantially to the sex differences reported in human cognitive and motor skills.

Reciprocal effects of hormonal fluctuations on human motor and perceptual-spatial skills.

Reciprocal effects of hormonal fluctuations on human motor and perceptual-spatial skills.

Historical review and appraisal of research on the learning, retention, and transfer of human motor skills.

Historical review and appraisal of research on the learning, retention, and transfer of human motor skills.

Historical review and appraisal of research on the learning, retention, and transfer of human motor skills.

This review of human motor skills is historical and critical, and starts about 100 years ago. Three historical periods are identified. The main topics are knowledge of results, distribution of practice, transfer of training, retention, and individual differences in motor learning. Basic research is emphasized, but applied research is included also. The article concludes with projections for the future that are based on past research and the present research climate. Why review nearly a century of research on motor skills? A good experiment can result from bouncing off the last one or a small subset of experiments in the literature, so why bother with the panorama? Any good scientific question always seems to have a long story. Perceptive investigators see the key variables and issues of a scientific topic early, and the generations that follow persist in efforts to understand those variables and issues. The first answer to my question, then, is that a sense of history helps an investigator lock onto important themes. Experiments enriched by history could contribute to the science rather than only brightening an inconsequential corner. Second, a sense of history tends to shunt an investigator away from the fads and fashions of his or her field. Fads and fashions are those inconsequential corners that are temporarily magnified out of proportion and that draw the energy of investigators who either have not seen the worth of persisting themes or who allow themselves to be turned from them. Third, the canons of scholarship are based on history because they require that (a) the origins of ideas be known so that one's own ideas are in perspective and, (b) earlier experiments be known so that the knowledge increment in one's own empirical findings is clear. My aim is to organize variables and issues for learning, retention, and transfer that have regularly attracted investigators of human motor skills, and to discuss the experiments that have been done to understand them. The last historical review of human motor skills was by Irion (1966). My review differs from Irion's in that I cover more material, have a different perspective, and update developments in the field. This article begins with a definition of the domain, and then divides the historical coverage into three historical periods: the Early Period, 1880-1940; the Middle Period, 19401970; and the Present Period, 1970 to the present. The periods are delineated by surges in research activity, although I cannot always be strict about the dividing line. The surge associated

Two quantitative measures of skill development.

Human perceptual motor skill development in tracking performance, using feedback control system gain and effective time delay as measures