Planning a trajectory and clearing obstacles - a bibliography

Visual planning for locomotion includes judgment of:

  • Obstacles distance, size and height relative to body size as well as skill level 
  • Gap size 
  • Slope 
  • Surface properties – slippery, soft, firm. stable 
Visually guided “passability” judgments depend on the perceived skill required to cross an obstacle, and the perceived size of the obstacle relative to one’s own body dimensions. 
 
These judgments become more refined during early childhood: For example, older toddlers judge better than younger toddlers whether a barrier can be stepped over (Schmuckler 1996) or a gap crossed (Zwart et al. 2005). 
 
By mid- childhood this body-referenced size information is very tightly coupled to passability judgments  
 
Pre-planning for obstacle clearance 
  • Involves determining the the height and distance to the obstacle
  • Planning appropriate foot placement and limb elevation for successful clearance. 
Gaze during the execution of such adaptive gait tasks is intermittently directed at the obstacle during the approach to it but the obstacle is not fixated during the step before or over the obstacle, and for the rest of the time gaze is directed on the ground ahead.. (Buckley et al 2011)
 
Information gathering for stepping down 
 
Descending kerbs is an example  obstacle negotiation during ongoing gait that involves the regulation of appropriate foot placement before the kerb-edge and foot clearance over it. It also involves the modulation of gait output to ensure the body-mass is safely and smoothly lowered to a new level. 
 
“Indeed, most of us will have experienced stepping from a kerb we had not anticipated. The shock force generated travels up the leg to the base of the spine and is experienced as an uncomfortable ‘jolt’ to the lower back. Thus predicting at what height and hence when contact with the lower level occurs are critical factors . These factors determine how and when the leading limb needs to be prepared for landing in order to safely and smoothly attenuate the increased downward momentum generated in lowering the body-mass to a new level; so that normal level walking can resume with minimal delay or perturbation. 
 
Vision has a predominant role in determining these critical factors  with vision from the lower visual field (lvf) being particularly important.
 
Gaze during adaptive gait is directed two or more walking steps ahead.  This implies that when descending a kerb during ongoing gait, an individual is unlikely to look directly at their feet or the area on the ground they intend to step onto. Although gaze may be directed ahead, visual feedback of the lower-limb and/or floor area immediately in front/below the foot will be available from the lvf. Such feedback has been shown to be used online during obstacle crossing to update foot placement before the obstacle and toe clearance over it , as well as detect the presence of an unexpectedly appearing obstacle. 
 
Extracted from Buckley et al 2011 
 
Experience of gradient and cliffs does not generalise from crawling to walking 
 
Bibliography 
Adolph, K. E., et al  (2010). How Do You Learn to Walk ? Thousands of Steps and Dozens of Falls Per Day.

Buckley, J. G., Timmis, M. a, Scally, A. J., & Elliott, D. B. (2011). When is visual information used to control locomotion when descending a kerb? PloS one, 6(4), e19079.

Descending kerbs during locomotion involves the regulation of appropriate foot placement before the kerb-edge and foot clearance over it. It also involves the modulation of gait output to ensure the body-mass is safely and smoothly lowered to the new level. Previous research has shown that vision is used in such adaptive gait tasks for feedforward planning, with vision from the lower visual field (lvf) used for online updating. The present study determined when lvf information is used to control/update locomotion when stepping from a kerb.

Cisek, P., & Kalaska, J. F. (2010). Neural Mechanisms for Interacting with a World Full of Action Choices. Annual Review of Neuroscience, (March), 269–298.

Wilmut, K., & Barnett, A. L. (2011). Locomotor behaviour of children while navigating through apertures. Experimental brain research.  210(2), 185–94. 

During everyday locomotion, we encounter a range of obstacles requiring specific motor responses; a narrow aperture which forces us to rotate our shoulders in order to pass through is one example. In adults, the decision to rotate their shoulders is body scaled (Warren and Whang in J Exp Psychol Hum Percept Perform 13:371-383, 1987), and the movement through is temporally and spatially tailored to the aperture size (Higuchi et al. in Exp Brain Res 175:50-59, 2006; Wilmut and Barnett in Hum Mov Sci 29:289-298, 2010). The aim of the current study was to determine how 8-to 10-year-old children make action judgements and movement adaptations while passing through a series of five aperture sizes which were scaled to body size (0.9, 1.1, 1.3, 1.5 and 1.7 times shoulder width). Spatial and temporal characteristics of movement speed and shoulder rotation were collected over the initial approach phase and while crossing the doorway threshold. In terms of making action judgements, results suggest that the decision to rotate the shoulders is not scaled in the same way as adults, with children showing a critical ratio of 1.61. Shoulder angle at the door could be predicted, for larger aperture ratios, by both shoulder angle variability and lateral trunk variability. This finding supports the dynamical scaling model (Snapp-Childs and Bingham in Exp Brain Res 198:527-533, 2009). In terms of movement adaptations, we have shown that children, like adults, spatially and temporally tailor their movements to aperture size.

Deconinck, F. J. a, Savelsbergh, G. J. P., De Clercq, D., & Lenoir, M. (2010)Balance problems during obstacle crossing in children with evelopmental Coordination Disorder. Gait & posture, 32(3), 327–31.

The present study investigated the visuomotor and balance limitations during obstacle crossing in typically developing (TD) children and those with Developmental Coordination Disorder (DCD) (7-9 years old; N=12 per group). Spatiotemporal gait parameters as well as range and velocity of the centre of mass (COM) were determined in three conditions: overground walking at a self-selected speed, crossing a low obstacle and crossing a high obstacle (5% or 30% of the leg length, respectively). Both groups walked more slowly during obstacle crossing than walking over level ground. In addition, both groups exhibited a significant decrease in the spatial variability of their foot placements as they approached the obstacle, which was then negotiated with a similar strategy. There were no differences in approach distance, length of lead and trail step, or lead and trail foot elevation. Compared to walking over level ground, obstacle crossing led to a longer swing phase of the lead and trail foot and increased maximal medio-lateral COM velocity. In children with DCD, however, medio-lateral COM velocity was higher and accompanied by significantly greater medio-lateral COM amplitude. In conclusion, the results indicate that while TD-children and those with DCD exhibit satisfactory anticipatory control and adequate visual guidance, the DCD group have a reduced ability to control the momentum of the COM when crossing obstacles that impose increased balance demands.

Hayhoe, M., & Ballard, D. (2005). Eye movements in natural behavior. Trends in cognitive sciences, 9(4), 188–94. doi:10.1016/j.tics.2005.02.009

Ingram, J. N., & Wolpert, D. M. (2011). Naturalistic approaches to sensorimotor control. Progress in brain research, 191, 3–29. 

Michel, J., Grobet, C., Dietz, V., & Van Hedel, H. J. a. (2010). Obstacle stepping in children: task acquisition and performance. Gait & posture, 31(3), 341–6. 

The aim of this study was to investigate the locomotor capacity of children during the performance of different lower extremity tasks with increasing difficulty. Two subject groups of children (aged 6-8 and 9-12 years) and adult controls performed several motor tasks from the Zürich Neuromotor Assessment (ZNA) test, as well as a unilateral and bilateral obstacle stepping test during treadmill walking. Performance of ZNA items, changes in foot clearance, and obstacle hits were assessed. Correlations between children's age, ZNA and obstacle measures were calculated. Performance of all motor tasks improved with increasing age. All three groups improved foot clearance during unilateral obstacle stepping, while the younger children achieved a poorer performance level. During bilateral obstacle stepping, only the adult controls and the 9-12 years old children's group further improved foot clearance, while no further improvement occurred in the 6-8 years old children's group. A relationship between items of ZNA and bilateral obstacle stepping was found. It is concluded that children in the mid-childhood range are able to significantly improve performance of a high-precision locomotor task. However, children below 9 years of age have a poorer motor performance compared to older children and adults that becomes more pronounced with increasing complexity of the task. Finally, ZNA tests can improve the prediction of complex adaptive locomotor behaviour compared to calendar age alone.

M Nardini & D Cowie (2012). The development of multisensory balance, locomotion, orientation and navigation. In Multisensory Development, A Bremner, D Lewkowicz & C Spence (Eds), Oxford University Press.  PDF

See also  Marko Nardini's lab page   

This chapter describes development of the sensory processes underlying the movement of our bodies in space. In order to move around the world in an adaptive manner infants and children must overcome a range of sensory and motor challenges. Since balance is a pre-requisite for whole-body movement and locomotion, a primary challenge is using sensory inputs to maintain balance. The ultimate goal of movement is to reach (or avoid) specific objects or locations in space. Thus, a further pre- requisite for adaptive spatial behaviour is the ability to represent the locations of significant objects and places. Information about such objects, and about one’s own movement (“self-motion”) comes from many different senses. A crucial challenge for infants and children (not to mention adults) is to select or integrate these correctly to perform spatial tasks. 
 

Rhea, C. K., Rietdyk, S., & Haddad, J. M. (2010). Locomotor adaptation versus perceptual adaptation when stepping over an obstacle with a height illusion. PloS one, 5(7),  e11544.  PDF

During locomotion, vision is used to perceive environmental obstacles that could potentially threaten stability; locomotor action is then modified to avoid these obstacles. Various factors such as lighting and texture can make these environmental obstacles appear larger or smaller than their actual size. It is unclear if gait is adapted based on the actual or perceived height of these environmental obstacles. The purposes of this study were to determine if visually guided action is scaled to visual perception, and to determine if task experience influenced how action is scaled to perception.

Wilmut, K., & Barnett, A. L. (2011). Locomotor behaviour of children while navigating through apertures. Experimental brain research. 210(2), 185–94.  k.wilmut@brookes.ac.uk

During everyday locomotion, we encounter a range of obstacles requiring specific motor responses; a narrow aperture which forces us to rotate our shoulders in order to pass through is one example. In adults, the decision to rotate their shoulders is body scaled (Warren and Whang in J Exp Psychol Hum Percept Perform 13:371-383, 1987), and the movement through is temporally and spatially tailored to the aperture size (Higuchi et al. in Exp Brain Res 175:50-59, 2006; Wilmut and Barnett in Hum Mov Sci 29:289-298, 2010). The aim of the current study was to determine how 8-to 10-year-old children make action judgements and movement adaptations while passing through a series of five aperture sizes which were scaled to body size (0.9, 1.1, 1.3, 1.5 and 1.7 times shoulder width). Spatial and temporal characteristics of movement speed and shoulder rotation were collected over the initial approach phase and while crossing the doorway threshold. In terms of making action judgements, results suggest that the decision to rotate the shoulders is not scaled in the same way as adults, with children showing a critical ratio of 1.61. Shoulder angle at the door could be predicted, for larger aperture ratios, by both shoulder angle variability and lateral trunk variability. This finding supports the dynamical scaling model (Snapp-Childs and Bingham in Exp Brain Res 198:527-533, 2009). In terms of movement adaptations, we have shown that children, like adults, spatially and temporally tailor their movements to aperture size.