Young Adults Are Impacted by the Spatial Context of Visual Cues to Perform Walking Turns.

Walking turns require coordinated axial segment rotations combined with step placement modifications. Visual information can inform this coordination and is used in three stages of processing: to identify the stimulus, select the appropriate response, and execute the response. We adapted a Simon task protocol to explore how response selection impacts walking turn execution. Young adults (n = 24; 15 female; 24.9 ± 4.5 years) completed walking turns to goals located 60 degrees left or right of their walking path. In some trials, heel contact with a force plate triggered appearance of an arrow on the same side (congruent), opposite side (incongruent) or in the middle (neutral) of a screen. To determine impact of different biomechanical demands for task execution, researchers specified which foot to initiate gait for each trial; this ensured visual cues were triggered either by the same limb as the turn direction (ipsilateral) or opposite (contralateral). We observed that head and trunk yaw motion was initiated earlier and with greater relative rotation magnitude for incongruent visual cues. Step width adaptations were also observed for both step patterns when responding to incongruent visual cues. Conflict at the response selection phase of visual processing disrupts typical turning behaviors of young adults.