Gazing Down Has benefits Unrelated to Visual Input

Recent reports have revealed that downward gazing enhances postural control. The mechanism underlying this phenomenon is currently unknown, yet there are several plausible explanations. In this study, we attempt to provide evidence to support the hypothesis that this effect is primarily derived from altered visual flow caused by gazing down. To this end, we quantified standing postural sway of 20 healthy participants and 20 people with stroke who were instructed to stand as still as possible under different conditions: while gazing forward and gazing down, with their eyes open and eyes closed. Both the horizontal gaze angle and the lack of visual input had a negative effect on participants ability to attenuate their body sway. Yet, the effect of gaze angle was constant regardless of the presence or absence of visual input. Also, people with stroke swayed more than their healthy counterparts and were more sensitive to the effect of gaze angle, but not to that of visual input. The results of this study indicate that downward gazing enhances postural control even in the absence of visual input and do not support our main hypothesis. Also, it seems that the effect of downward gazing on postural control is greater in unstable people (people with stroke) than that observed in healthy adults, which might explain less stable individuals tendency to gaze down while walking. Furthermore, these results might suggest that downward gazing behavior does not necessarily indicate an attempt to acquire visual information of any kind but instead serves to modulate some other sensory input helpful for postural control.