Coordination of eye and leg movements during visually guided stepping

In the present study, 2 related hypotheses were tested: first, that vision is used in a feedforward control mode during precision stepping onto visual targets and, second, that the oculomotor and locomotor control centers int eract to produce coordinated eye and leg movements during that task. Partic ipants' (N = 4) eye movements and step cycle transition events were monitor ed while they performed a task requiring precise foot placement at every st ep onto irregularly placed stepping stones under conditions in which the av ailability of visual information was either restricted or intermittently re moved altogether. Accurate saccades, followed by accurate steps, to the nex t footfall target were almost always made even when the information had bee n invisible for as long as 500 ms. Despite delays in footlift caused by the temporary removal (and subsequent reinstatement) of visual information, th e mean interval between the start of the eye movement and the start of the swing toward a target did not vary significantly (p > .05). In contrast, th e mean interval between saccade onset away from a target and a foot landing on that target (stance onset) did vary significantly (p < .05) under the d ifferent experimental conditions. Those results support the stated hypothes es.