Roles of glabrous skin receptors and sensorimotor memory in automatic control of precision grip when lifting rougher or more slippery objects
TL;DR: The present paper deals quantitatively with the regulation of the coordination between the grip force and the vertical lifting force, denoted as the load force, while small objects were lifted, positioned in space and replaced by human subjects using the pinch grip.
Abstract: To be successful, precision manipulation of small objects requires a refined coordination of forces excerted on the object by the tips of the fingers and thumb. The present paper deals quantitatively with the regulation of the coordination between the grip force and the vertical lifting force, denoted as the load force, while small objects were lifted, positioned in space and replaced by human subjects using the pinch grip. It was shown that the grip force changed in parallel with the load force generated by the subject to overcome various forces counteracting the intended manipulation. The balance between the two forces was adapted to the friction between the skin and the object providing a relatively small safety margin to prevent slips, i.e. the more slippery the object the higher the grip force at any given load force. Experiments with local anaesthesia indicated that this adaptation was dependent on cutaneous afferent input. Afferent information related to the frictional condition could influence the force coordination already about 0.1 s after the object was initially gripped, i.e. approximately at the time the grip and load forces began to increase in parallel. Further, “secondary”, adjustments of the force balance could occur later in response to small short-lasting slips, revealed as vibrations in the object. The new force balance following slips was maintained, indicating that the relationship between the two forces was set on the basis of a memory trace. Its updating was most likely accounted for by tactile afferent information entering intermittently at inappropriate force coordination, e.g. as during slips. The latencies between the onset of such slips and the appearance of the adjustments (0.06–0.08 s) clearly indicated that the underlying neural mechanisms operated highly automatically.
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TL;DR: The 'minimum variance model' is another major recent advance in the computational theory of motor control, strongly suggesting that both kinematic and dynamic internal models are utilized in movement planning and control.
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TL;DR: Electronic networks comprised of flexible, stretchable, and robust devices that are compatible with large-area implementation and integrated with multiple functionalities is a testament to the progress in developing an electronic skin akin to human skin.
Abstract: Human skin is a remarkable organ. It consists of an integrated, stretchable network of sensors that relay information about tactile and thermal stimuli to the brain, allowing us to maneuver within our environment safely and effectively. Interest in large-area networks of electronic devices inspired by human skin is motivated by the promise of creating autonomous intelligent robots and biomimetic prosthetics, among other applications. The development of electronic networks comprised of flexible, stretchable, and robust devices that are compatible with large-area implementation and integrated with multiple functionalities is a testament to the progress in developing an electronic skin (e-skin) akin to human skin. E-skins are already capable of providing augmented performance over their organic counterpart, both in superior spatial resolution and thermal sensitivity. They could be further improved through the incorporation of additional functionalities (e.g., chemical and biological sensing) and desired properties (e.g., biodegradability and self-powering). Continued rapid progress in this area is promising for the development of a fully integrated e-skin in the near future.
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TL;DR: Analysis of signals in tactile afferent neurons and central processes in humans reveals how contact events are encoded and used to monitor and update task performance.
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1,569 citations
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01 Jan 1966
TL;DR: This book discusses statistical decision theory and sensory processes in signal detection theory and psychophysics and describes how these processes affect decision-making.
Abstract: Book on statistical decision theory and sensory processes in signal detection theory and psychophysics
11,820 citations
1,269 citations
TL;DR: The intent of this study was to discover the stabilizing role of stretch reflexes acting upon the ankle musculature while human subjects performed stance tasks requiring several different postural “sets”.
Abstract: Doubt about the role of stretch reflexes in movement and posture control has remained in part because the questions of reflex “usefulness” and the postural “set” have not been adequately considered in the design of experimental paradigms. The intent of this study was to discover the stabilizing role of stretch reflexes acting upon the ankle musculature while human subjects performed stance tasks requiring several different postural “sets”. Task specific differences of reflex function were investigated by experiments in which the role of stretch reflexes to stabilize sway during stance could be altered to be useful, of no use, or inappropriate. Because the system has available a number of alternate inputs to posture (e.g., vestibular and visual), stretch reflex responses were in themselves not necessary to prevent a loss of balance. Nevertheless, 5 out of 12 subjects in this study used long-latency (120 msec) stretch reflexes to help reduce postural sway. Following an unexpected change in the usefulness of stretch reflexes, the 5 subjects progressively altered reflex gain during the succeeding 3–5 trials. Adaptive changes in gain were always in the sense to reduce sway, and therefore could be attenuating or facilitating the reflex response. Comparing subjects using the reflex with those not doing so, stretch reflex control resulted in less swaying when the task conditions were unchanging. However, the 5 subjects using reflex controls oftentimes swayed more during the first 3–5 trials after a change, when inappropriate responses were elicited. Four patients with clinically diagnosed cerebellar deficits were studied briefly. Among the stance tasks, their performance was similar to normal in some and significantly poorer in others. Their most significant deficit appeared to be the inability to adapt long-latency reflex gain following changes in the stance task. The study concludes with a discussion of the role of stretch reflexes within a hierarchy of controls ranging from muscle stiffness up to centrally initiated responses.
997 citations
"Roles of glabrous skin receptors an..." refers background in this paper
...…e.g. during alterations of gain of the vestibular reflex (e.g. Miles and Fuller 1974; Ito 1976; Gonshor and Melville Jones 1976a, b; Robinson 1976) and adaptation of the body and limbs to perturbations of maintained position (e.g. Nashner 1976; Gilbert and Thach 1977; Nashner and Grimm 1978 )....
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...…to reach a complete adaptation, the adaptation of force coordination in our experiments appear to proceed even quicker (second trial) than the adaptation of the gain of the "functional stretch reflex" following an unexpected change in its usefulness to stabilize sway during stance (Nashner 1976)....
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TL;DR: It was found that the applied grip force was critically balanced to optimize the motor behaviour so that slipping between the skin and the gripped object did not occur and the grip force did not reach exeedingly high values.
Abstract: A small object was gripped between the tips of the index finger and thumb and held stationary in space. Its weight and surface structure could be changed between consecutive lifting trials, without changing its visual appearance. The grip force and the vertical lifting force acting on the object, as well as the vertical position of the object were continuously recorded. Likewise, the minimal grip force necessary to prevent slipping, was measured. The difference between this minimal force and the employed grip force, was defined as the safety margin to prevent slipping.
954 citations
"Roles of glabrous skin receptors an..." refers background or methods or result in this paper
...1, was a modified version of one described earlier (Westling and Johansson 1984)....
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...In their absence, the grip force and thereby the safety margin remained slightly lower throughout these trials than during suede trials preceded by suede trials (cf. Westling and Johansson 1984)....
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...Recently, however, one specific functional role immediately related to the gripping function of the hand has been suggested for cutaneous afferent input (Westling and Johansson 1984)....
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...The variation in safety margin between subjects (see Westling and Johansson 1984) may be related to differences in a performance criterion, just as the decision criterion influence the costs and payoff during, for instance, a psychophysical discrimination task (e.g. Green and Sweets 1966)....
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...To restrict possible influences from a different frictional condition in the previous trial (see Westling and Johansson 1984), the hitherto analysis of the force coordination was based on trials whose previous trials were carried out using the same surface structure, respectively, i.e. these trials…...
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TL;DR: It is shown that a man deafferented by a severe peripheral sensory neuropathy could produce a very wide range of preprogrammed finger movements with remarkable accuracy, involving complex muscle synergies of the hand and forearm muscles.
Abstract: We have studied manual motor function in a man deafferented by a severe peripheral sensory neuropathy Motor power was almost unaffected Our patient could produce a very wide range of preprogrammed finger movements with remarkable accuracy, involving complex muscle synergies of the hand and forearm muscles He could perform individual finger movements and outline figures in the air with his eyes closed He had normal pre- and postmovement EEG potentials, and showed the normal bi/triphasic pattern of muscle activation in agonist and antagonist muscles during fast limb movements He could also move his thumb accurately through three different distances at three different speeds, and could produce three different levels of force at his thumb pad when required Although he could not judge the weights of objects placed in his hands without vision, he was able to match forces applied by the experimenter to the pad of each thumb if he was given a minimal indication of thumb movement
Despite his success with these laboratory tasks, his hands were relatively useless to him in daily life He was unable to grasp a pen and write, to fasten his shirt buttons or to hold a cup in one hand Part of his difficulty lay in the absence of any automatic reflex correction in his voluntary movements, and also to an inability to sustain constant levels of muscle contraction without visual feedback over periods of more than one or two seconds He was also unable to maintain long sequences of simple motor programmes without vision
829 citations
"Roles of glabrous skin receptors an..." refers background in this paper
...The overall importance of somatosensory afferent signals for automatic adjustments or "fine tuning" of preporgrammed muscle commands and for updating of motor programmes during manual motor activities has recently been emphasized in a unique study of a deafferented man (Rothwell et al. 1982)....
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...emphasized in a unique study of a deafferented man (Rothwell et al. 1982)....
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