Changes in the Limb Kinematics and Walking-Distance Estimation After Shank Elongation: Evidence for a Locomotor Body Schema?

Dominici, Nadia; Daprati, Elena; Nico, Daniele; Cappellini, Germana; Ivanenko, Yuri P.; Lacquaniti, Francesco

doi:10.1152/jn.91165.2008

Cited by 37 publications

(35 citation statements)

References 51 publications

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“…Clearly, position sense does not rely on proprioceptive information alone, but supplements this with vision (29,30) and efferent copies of motor commands (31). Motor learning might involve correcting a distorted underlying model with these additional inputs, analogous to adaptive changes following exposure to visually distorting prisms (32) or surgical elongation of limbs (33). Our experiments removed these two potentially enriching inputs to the represented body.…”

Section: Discussionmentioning

confidence: 99%

An implicit body representation underlying human position sense

Longo

Haggard

2010

Proc. Natl. Acad. Sci. U.S.A.

322

378

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Knowing the body's location in external space is a fundamental perceptual task. Perceiving the location of body parts through proprioception requires that information about the angles of each joint (i.e., body posture) be combined with information about the size and shape of the body segments between joints. Although information about body posture is specified by on-line afferent signals, no sensory signals are directly informative about body size and shape. Thus, human position sense must refer to a stored body model of the body's metric properties, such as body part size and shape. The need for such a model has long been recognized; however, the properties of this model have never been systematically investigated. We developed a technique to isolate and measure this body model. Participants judged the location in external space of 10 landmarks on the hand. By analyzing the internal configuration of the locations of these points, we produced implicit maps of the mental representation of hand size and shape. We show that this part of the body model is massively distorted, in a reliable and characteristic fashion, featuring shortened fingers and broadened hands. Intriguingly, these distortions appear to retain several characteristics of primary somatosensory representations, such as the Penfield homunculus.body image | proprioception | postural schema | body representation P erceiving the body's location in external space is essential for interacting with our environment and for constructing a coherent sense of self. Proprioceptive signals from afferents in muscles, joints, and skin provide information about joint flexion or extension (1, 2), contributing to a representation of body posture, the postural schema (3). To perceive the absolute position of body parts in external space, however, this postural information must be combined with information about the size and shape of the body segments connecting the joints (4-8) (Fig. 1A). No sensory signal, however, directly informs the brain about the metric properties of body parts. Thus, localization of the body in external space requires that on-line afferent signals specifying joint angles be informed by a stored body model. Although several researchers have identified the need for such a body model (4,6,8), no attempt has been made to measure this model, and its properties are unknown. Here, we systematically investigate the body model mediating position sense of the human hand, showing that it is massively distorted, and appears to retain distortions characteristic of the somatosensory homunculus.The essential contribution of the body model to position sense is specifying the relative locations of body parts. The overall "localization error" for a single landmark (i.e., the distance between actual and judged locations) depends on several factors. In contrast, the distance between the judged locations of two adjacent landmarks (e.g., the tip and knuckle of a single finger) depends only on the represented length of the body segment connecting them. Other sources o...

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Section: Discussionmentioning

confidence: 99%

An implicit body representation underlying human position sense

Longo

Haggard

2010

Proc. Natl. Acad. Sci. U.S.A.

322

378

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“…Locomotor commands must take these changes into account to keep limb segment motion calibrated with body size. The importance of a body scheme incorporating limb and body parameters is demonstrated by the observation that an 11-years-old child, who underwent surgical elongation of the shanks by >50%, walked as if on the pre-surgery shorter legs, just as do adults walking on stilts [66].…”

Section: Learning and Explorationmentioning

confidence: 99%

Development of human locomotion

Lacquaniti¹,

Ivanenko²,

Zago³

2012

Current Opinion in Neurobiology

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Neural control of locomotion in human adults involves the generation of a small set of basic patterned commands directed to the leg muscles. The commands are generated sequentially in time during each step by neural networks located in the spinal cord, called Central Pattern Generators. This review outlines recent advances in understanding how motor commands are expressed at different stages of human development. Similar commands are found in several other vertebrates, indicating that locomotion development follows common principles of organization of the control networks. Movements show a high degree of flexibility at all stages of development, which is instrumental for learning and exploration of variable interactions with the environment

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“…Contact with the ground occurred at the lower part (floor plate) of the parallelepiped. The shank segment was fixed to the upper leg support strut using a wide belt, while the foot was fixed to the footplate of the rotational parallelepiped, allowing rotary motion of the ankle joint [see Dominici et al and Singer et al for a detailed description of this type of stilt (Dominici et al, 2009;Singer et al, 2011). The 40cm shank elongation caused the total limb length to be increased accordingly.…”

Section: Stiltsmentioning

confidence: 99%

“…If, in contrast, the optimal speed changes, we would argue that it is more likely that compensatory mechanisms play an important role in the adjustment of the limb geometry and optimal energetics of terrestrial locomotion in accordance with the Fr number of 0.25. In addition, such investigations may have important implications related to the construction of biologically inspired robots (Pfeifer et al, 2007) and clinical studies (Dominici et al, 2009;Kuo and Donelan, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…The issue of evolutionarily adopted 'optimization' of body geometry has also recently received attention with regard to the so-called locomotor body scheme (Dominici et al, 2009;Pearson and Gramlich, 2010;Ivanenko et al, 2011a). Walking on stilts represents an interesting example of gait adaptation and reorganization of locomotor patterns (Vaida et al, 1981;Wittlinger et al, 2006;Chiou et al, 2008;Akram and Frank, 2009;Dominici et al, 2009;Pan et al, 2009;Wu et al, 2009;Singer et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

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Optimal walking speed following changes in limb geometry

Leurs

Ivanenko

Bengoetxea

et al. 2011

Journal of Experimental Biology

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SUMMARYThe principle of dynamic similarity states that the optimal walking speeds of geometrically similar animals are independent of size when speed is normalized to the dimensionless Froude number (Fr). Furthermore, various studies have shown similar dimensionless optimal speed (Fr~0.25) for animals with quite different limb geometries. Here, we wondered whether the optimal walking speed of humans depends solely on total limb length or whether limb segment proportions play an essential role. If optimal walking speed solely depends on the limb length then, when subjects walk on stilts, they should consume less metabolic energy at a faster optimal speed than when they walk without stilts. To test this prediction, we compared kinematics, electromyographic activity and oxygen consumption in adults walking on a treadmill at different speeds with and without articulated stilts that artificially elongated the shank segment by 40cm. Walking on stilts involved a non-linear reorganization of kinematic and electromyography patterns. In particular, we found a significant increase in the alternating activity of proximal flexors-extensors during the swing phase, despite significantly shorter normalized stride lengths. The minimal metabolic cost per unit distance walked with stilts occurred at roughly the same absolute speed, corresponding to a lower Fr number (Fr~0.17) than in normal walking (Fr~0.25). These findings are consistent with an important role of limb geometry optimization and kinematic coordination strategies in minimizing the energy expenditure of human walking.

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Changes in the Limb Kinematics and Walking-Distance Estimation After Shank Elongation: Evidence for a Locomotor Body Schema?

Cited by 37 publications

References 51 publications

An implicit body representation underlying human position sense

An implicit body representation underlying human position sense

Development of human locomotion

Optimal walking speed following changes in limb geometry

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