Visual control of human gait during locomotor pointing

• Author / Creator

  Popescu, Adrian

• Daily locomotor tasks require gait adaptations in order to match various environmental challenges. Healthy individuals rely on vision in order to make proactive gait changes as vision is the sensory modality best suited to provide accurate information about distant environmental constraints. This dissertation was concerned with investigating the adaptive locomotor strategies and the related visual sampling characteristics during locomotor pointing tasks. These goals were achieved by conducting a series of four experiments requiring participants to walk towards and accurately point with the forefoot at distantly located targets without stopping. Young and older healthy participants performed the task in different environmental setups and under various visual sampling conditions. The results clearly demonstrate that the environmental information was sampled in a predictive manner for planning proactive stepping adjustments during the target approach and for extracting limb position information in relation with the target for fine-tuning the foot trajectory prior to foot-pointing. The results also indicate that discrete visual samples were adequate to complete the tasks. Generally, vision availability amounted to less than half of the trial duration for each trial and the typical sampling strategy consisted of one or two brief visual samples such that vision was available almost all the time during the pointing step. The gaze was deployed towards targets well in advance of the foot-pointing action and it remained anchored there until about the time the foot contacted that particular target. Participants typically undershot the targets and the likelihood of overshooting the targets significantly changed with the increase in task difficulty and complexity. Older adults prematurely disengaged the gaze from the targets, consequently increasing the likelihood of target overshooting. This may indicate that the older adults need more time to plan and implement gait modulations and could be interpreted as a sign of future, naturally-occurring, and more dramatic changes in visuomotor control during adaptive locomotion. In conclusion, this work shows the existence of well-preserved yet flexible motor control strategies related to locomotor pointing tasks. With aging, these visuomotor strategies lose their effectiveness and become one of the causes liable for the increase in the rate of falling occurrences for older adults.

• Subjects / Keywords

  • Head-free gaze
  • Task complexity
  • Visuomotor control
  • Intermittent vision
  • Adaptive locomotion

• Graduation date

  Spring 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3JP94

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.