Saccade-stepping interactions revise the motor plan for obstacle avoidance.
The authors used a stimulus-response compatibility paradigm to assess the effect of changing the estimated time to obstacle contact. A limb-selection cue was presented in different phases of gait to young (n = 5) and to older (n = 4) adults while they were moving toward a foam obstacle in the walking path. A downward saccade was initiated after the cue; the saccade typically occurred during the stance phase of the target limb (the foot cued to lead the step over the obstacle). The mean saccade-step latency after the cue was on the order of -500 ms in both young and elderly participants. On reaching the obstacle, both groups generated an upward saccade approximately -300 ms before target footlift in both groups. Saccades following the limb-selection cue appeared to direct the gaze toward footfall targets just beyond the obstacle, whereas saccades generated just before obstacle footlift moved the gaze to the forward-looking direction. The elderly had significantly longer saccade-trailing-footlift latencies and prolonged gaze-fixation times than did the younger adults. Transient disruptions in optical flow appeared to be necessary for successful obstacle-avoidance behavior when there was an unexpected change in the estimated time to obstacle contact.
Di Fabio
Richard P
RP
Department of Physical Medicine & Rehabilitation, University of Minnesota School of Medicine, Minneapolis, MN 55455, USA. difab001@umn.edu
Greany
John F
JF
Zampieri
Cris
C
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000523:psychology*; D001362:Avoidance Learning; D001696:Biomechanical Phenomena; D005260:Female; D007839:Functional Laterality; D005684:Gait; D006801:Humans; D007699:Kinesthesis; D008297:Male; D009949:Orientation; D011340:Problem Solving; D011930:Reaction Time; D012438:Saccades; D016138:Walking