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1.1 The coupling between optical flow and neonatal stepping
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Chapter 1. Development of balance control [
•couplingT between h opticale flow and neonatal stepping
M. Barbu-Roth 1, M. Trujillo 2, A. Despr~s 1, D.I. Anderson 2, J. Provasi 3, L. Vaivre-Douret4, D. Cabrol 5. 1C~VRS UMR
8605-Universitd Paris' 5, France," 2San Francisco State University, USA," 3Laboratoire Ddveloppement et Complexitd-EPHE, France," 4U483 Inserm-Paris VI-H@ital Necker, France," 5Maternitd Port-Royal-Paris, France The ability to detect and control self motion based on patterns of optical flow is crucial to the control of posture and locomotion. However, little is know about the early coupling of vision and locomotion in infants. In the current experiments, we attempted to determine if terrestrial optical flow influenced neonatal stepping behavior. M e t h o d s : The number of steps taken by 48 3-day-old infants held in air stepping position was recorded for one minute in each of four randomly presented conditions of optic flow: 1) Terrestrial Flow, where a checkerboard, lamellar flow moved toward the infant, 2) Static Texture, where the checkerboard pattern was stationary, 3) Rotating Flow, where triangles rotated clockwise on the surface, and 4) Real Stepping, where the soles of the infant's feet contacted the support surface. Results: There were significant differences in the average number of steps taken per condition, F(3,66) 3.4, p <0.05. More steps were taken in the Terrestrial Flow condition than the Static Texture condition, in the Real Stepping condition than the Rotating Flow condition, and in the Real Stepping condition than the Static condition. A 2-Dimensional kinematic analysis indicated that neonates were more variable and stepped differently in the Terrestrial Flow condition than the other conditions. D i s c u s s i o n a n d c o n c l u s i o n : These findings suggest that newborns will make stepping movements even if their feet do not receive the tactile stimulation that was once thought necessary to elicit the stepping pattern. Moreover, air stepping was more easily elicited by terrestrial lamellar optical flow. Introduction:
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Multiple obstacle avoidance strategies in adults and mid-childhood aged children
J.R. Berard, L.A. Vallis. Department of Human Biology and Nutritional Sciences', University of Guelph, Canada I n t r o d u c t i o n : Few studies have investigated the influence of multiple
obstacles on locomotor strategies. Krell and Patla [1] found that a second obstacle in the travel path results in a change in gait parameters for both the first and second obstacle. Visual information is an important contributor during locomotor tasks and children are reportedly more reliant on visual information than adults [2]. The current work will expand our knowledge about the role of vision in adults and children when avoiding two obstacles placed in their travel path under altered ambient lighting. M e t h o d s : Ten adults and ten children (7 9 years) volunteered for the study. Subjects were instrumented with infrared markers (Optotrak, NDI) and asked to perform two locomotor tasks: unobstructed and obstructed walking (two obstacles, each 20cm high) under two lighting conditions: full and low light. From kinematic data, foot placement, centre of mass (CoM), and head and trunk angles were calculated. Results: Preliminary data indicates that adults have similar locomotor strategies for clearing both obstacles; values for foot placement parameters and peak CoM trajectory height were similar in the approach and clearance of both obstacles. Preliminary results
indicate that children have inconsistent step lengths and velocities as they approach each of the obstacles. D i s c u s s i o n s a n d C o n c l u s i o n s : We hypothesize that children will show greater variability in avoidance control strategies (e.g. segmental coordination, gait parameters) compared to adults, especially in low lighting conditions.
References [1] Krell J, Patla AE. Gait Posture 2002; 16:15 19. [2] Grasso R, Assaiante C, Prevost P, Berthoz A. Neurosci Biobehav Rev 1998; 22(4): 533 539.
[~
Gait kinematics in newly walking toddlers
N. D o m i n i c i 1,2, G. Cappellini 1 , Y.P. I v a n e n k o 1 , E Lacquaniti 1,2.
IlRCC~ Fondazione Santa Lucia, Rome, Italy; 2University of Rome Tor Vergata, Rome, Italy I n t r o d u c t i o n : When children start to walk without support, their body displays considerable oscillations due to poor equilibrium. Can postural instability represent a perturbing factor that prevents the expression of the mature coordination pattern in toddlers? M e t h o d s : To test this hypothesis, we performed several experimental maneuvers to stabilize the body in walking toddlers performing their first independent steps. To compare kinematic patterns, we used the methods developed earlier for adult's gait. R e s u l t s : Hand and trunk support significantly improved postural stability, reducing percent of falls, step width, lateral hip deviations and trunk oscillations. However, the kinematic patterns were unaffected by increased postural stability. In particular, the co-variance of the limb segment angular motion, the lack of the pendulum mechanism of walking, high foot path variability, the elliptic or single peak trajectory of the foot and characteristic EMG bursts at foot contact remained idiosyncratic of toddler locomotion. Gait kinematics remained basically unchanged until the occurrence of the first unsupported steps and rapidly matured thereafter. Discussion and C o n c l u s i o n The results suggest that gait immaturity in toddlers does not depend on postural imbalance. We conclude that idiosyncratic features in newly walking toddlers do not simply result from undeveloped balance control but may represent an innate kinematic template of stepping.
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Development of postural adjustments during infancy: evidence for a major transition at 6 months.'?
M. Hadders-Algra. Department of Neurology Developmental Neurology, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands' This paper reviews the development of postural adjustments during infancy. In the control of posture two functional levels can be distinguished. The basic level deals with the generation of direction specific adjustments: dorsal muscles are primarily activated when the body sways forward and ventral ones when the body sways backward. The second level is involved in adaptation of the direction specific adjustments. R e s u l t s : Postural development starts with a repertoire of direction specific adjustments suggesting that the basic level of control has an innate origin. At first, during the phase of primary variability, postural activity is largely variable and can be minimally adapted to environmental constraints. At 3 months postural activity shows a transient period during which few postural muscles participate in postural activity. From 6 months onwards the phase of secondary Introduction:
Chapter 1. Development of balance control [
•couplingT between h opticale flow and neonatal stepping
M. Barbu-Roth 1, M. Trujillo 2, A. Despr~s 1, D.I. Anderson 2, J. Provasi 3, L. Vaivre-Douret4, D. Cabrol 5. 1C~VRS UMR
8605-Universitd Paris' 5, France," 2San Francisco State University, USA," 3Laboratoire Ddveloppement et Complexitd-EPHE, France," 4U483 Inserm-Paris VI-H@ital Necker, France," 5Maternitd Port-Royal-Paris, France The ability to detect and control self motion based on patterns of optical flow is crucial to the control of posture and locomotion. However, little is know about the early coupling of vision and locomotion in infants. In the current experiments, we attempted to determine if terrestrial optical flow influenced neonatal stepping behavior. M e t h o d s : The number of steps taken by 48 3-day-old infants held in air stepping position was recorded for one minute in each of four randomly presented conditions of optic flow: 1) Terrestrial Flow, where a checkerboard, lamellar flow moved toward the infant, 2) Static Texture, where the checkerboard pattern was stationary, 3) Rotating Flow, where triangles rotated clockwise on the surface, and 4) Real Stepping, where the soles of the infant's feet contacted the support surface. Results: There were significant differences in the average number of steps taken per condition, F(3,66) 3.4, p <0.05. More steps were taken in the Terrestrial Flow condition than the Static Texture condition, in the Real Stepping condition than the Rotating Flow condition, and in the Real Stepping condition than the Static condition. A 2-Dimensional kinematic analysis indicated that neonates were more variable and stepped differently in the Terrestrial Flow condition than the other conditions. D i s c u s s i o n a n d c o n c l u s i o n : These findings suggest that newborns will make stepping movements even if their feet do not receive the tactile stimulation that was once thought necessary to elicit the stepping pattern. Moreover, air stepping was more easily elicited by terrestrial lamellar optical flow. Introduction:
[•
Multiple obstacle avoidance strategies in adults and mid-childhood aged children
J.R. Berard, L.A. Vallis. Department of Human Biology and Nutritional Sciences', University of Guelph, Canada I n t r o d u c t i o n : Few studies have investigated the influence of multiple
obstacles on locomotor strategies. Krell and Patla [1] found that a second obstacle in the travel path results in a change in gait parameters for both the first and second obstacle. Visual information is an important contributor during locomotor tasks and children are reportedly more reliant on visual information than adults [2]. The current work will expand our knowledge about the role of vision in adults and children when avoiding two obstacles placed in their travel path under altered ambient lighting. M e t h o d s : Ten adults and ten children (7 9 years) volunteered for the study. Subjects were instrumented with infrared markers (Optotrak, NDI) and asked to perform two locomotor tasks: unobstructed and obstructed walking (two obstacles, each 20cm high) under two lighting conditions: full and low light. From kinematic data, foot placement, centre of mass (CoM), and head and trunk angles were calculated. Results: Preliminary data indicates that adults have similar locomotor strategies for clearing both obstacles; values for foot placement parameters and peak CoM trajectory height were similar in the approach and clearance of both obstacles. Preliminary results
indicate that children have inconsistent step lengths and velocities as they approach each of the obstacles. D i s c u s s i o n s a n d C o n c l u s i o n s : We hypothesize that children will show greater variability in avoidance control strategies (e.g. segmental coordination, gait parameters) compared to adults, especially in low lighting conditions.
References [1] Krell J, Patla AE. Gait Posture 2002; 16:15 19. [2] Grasso R, Assaiante C, Prevost P, Berthoz A. Neurosci Biobehav Rev 1998; 22(4): 533 539.
[~
Gait kinematics in newly walking toddlers
N. D o m i n i c i 1,2, G. Cappellini 1 , Y.P. I v a n e n k o 1 , E Lacquaniti 1,2.
IlRCC~ Fondazione Santa Lucia, Rome, Italy; 2University of Rome Tor Vergata, Rome, Italy I n t r o d u c t i o n : When children start to walk without support, their body displays considerable oscillations due to poor equilibrium. Can postural instability represent a perturbing factor that prevents the expression of the mature coordination pattern in toddlers? M e t h o d s : To test this hypothesis, we performed several experimental maneuvers to stabilize the body in walking toddlers performing their first independent steps. To compare kinematic patterns, we used the methods developed earlier for adult's gait. R e s u l t s : Hand and trunk support significantly improved postural stability, reducing percent of falls, step width, lateral hip deviations and trunk oscillations. However, the kinematic patterns were unaffected by increased postural stability. In particular, the co-variance of the limb segment angular motion, the lack of the pendulum mechanism of walking, high foot path variability, the elliptic or single peak trajectory of the foot and characteristic EMG bursts at foot contact remained idiosyncratic of toddler locomotion. Gait kinematics remained basically unchanged until the occurrence of the first unsupported steps and rapidly matured thereafter. Discussion and C o n c l u s i o n The results suggest that gait immaturity in toddlers does not depend on postural imbalance. We conclude that idiosyncratic features in newly walking toddlers do not simply result from undeveloped balance control but may represent an innate kinematic template of stepping.
[•
Development of postural adjustments during infancy: evidence for a major transition at 6 months.'?
M. Hadders-Algra. Department of Neurology Developmental Neurology, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands' This paper reviews the development of postural adjustments during infancy. In the control of posture two functional levels can be distinguished. The basic level deals with the generation of direction specific adjustments: dorsal muscles are primarily activated when the body sways forward and ventral ones when the body sways backward. The second level is involved in adaptation of the direction specific adjustments. R e s u l t s : Postural development starts with a repertoire of direction specific adjustments suggesting that the basic level of control has an innate origin. At first, during the phase of primary variability, postural activity is largely variable and can be minimally adapted to environmental constraints. At 3 months postural activity shows a transient period during which few postural muscles participate in postural activity. From 6 months onwards the phase of secondary Introduction: