Obstacle Crossing Differences Between Blind and Blindfolded Subjects After Haptic Exploration

Abstract

Little is known about the ability of blind people to cross obstacles after they have explored haptically their size and position. Long-term absence of vision may affect spatial cognition in the blind while their extensive experience with the use of haptic information for guidance may lead to compensation strategies. Seven blind and 7 sighted participants (with vision available and blindfolded) walked along a flat pathway and crossed an obstacle after a haptic exploration. Blind and blindfolded subjects used different strategies to cross the obstacle. After the first 20 trials the blindfolded subjects reduced the distance between the foot and the obstacle at the toe-off instant, while the blind behaved as the subjects with full vision. Blind and blindfolded participants showed larger foot clearance than participants with vision. At foot landing the hip was more behind the foot in the blindfolded condition, while there were no differences between the blind and the vision conditions. For several parameters of the obstacle crossing task, blind people were more similar to subjects with full vision indicating that the blind subjects were able to compensate for the lack of vision.

Walking with perturbations: a guide for biped humans and robots

“…Subjects with impaired vision use higher toe-clearance and increased distance between foot and obstacle at foot placement [249,250]. It can also be noted that these adjustments are different between blind and blindfolded people, indicating a long-term adaptation to visual deprivation [252].…”

“…In particular, keeping the hip backwards while crossing the obstacle is the preferred control strategy of bipedal robots using the Zero Moment Point stability criterion [232]. Interestingly, such behavior is also seen in blindfolded subject, when avoiding obstacles [252].…”

“…When vision is restricted or abolished one can still avoid obstacles provided haptic information is added, for example such as provided by a cane [250]. When tactile information about obstacle position can be gathered beforehand, the crossing of the obstacles can also be performed successfully [251]. Otherwise, adjustments to the obstacle avoidance can be found.…”

Children with Duchenne muscular dystrophy display specific kinematic strategies during obstacle-crossing

“…Significantly reduced trailing toe-obstacle clearance indicates an increased risk of tripping in children with DMD, especially because neither the swing-limb nor the obstacle is within the subject's visual field during trailing-limb crossing 32 . Vision integrates predicting the relative positions of the body segment and the obstacle during crossing, and visual feedback significantly influences the end-point control strategy during obstaclecrossing 66 , without which the risk of tripping would be increased 67 . Children with DMD were found to rely on visual feedback for motor control because they showed compromised manipulation abilities, especially in the With the stance-foot immobilized on the ground, the sub-figures were obtained by rotating the distal part of the pelvis-leg apparatus at one joint at a time while keeping the other joints immobilized according to the significant angular changes reported in Table 3.…”