Is “circling” behavior in humans related to postural asymmetry?
PLoS ONE. 2012-09-05; 7(9): e43861
DOI: 10.1371/journal.pone.0043861
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In attempting to walk rectilinearly in the absence of visual landmarks, persons
will gradually turn in a circle to eventually become lost. The aim of the present
study was to provide insights into the possible underlying mechanisms of this
behavior. For each subject (N = 15) six trajectories were monitored during
blindfolded walking in a large enclosed area to suppress external cues, and
ground irregularities that may elicit unexpected changes in direction. There was
a substantial variability from trial to trial for a given subject and between
subjects who could either veer very early or relatively late. Of the total number
of trials, 50% trajectories terminated on the left side, 39% on the right side
and 11% were defined as “straight”. For each subject, we established a “turning
score” that reflected his/her preferential side of veering. The turning score was
found to be unrelated to any evident biomechanical asymmetry or functional
dominance (eye, hand…). Posturographic analysis, used to assess if there was a
relationship between functional postural asymmetry and veering revealed that the
mean position of the center of foot pressure during balance tests was correlated
with the turning score. Finally, we established that the mean position of the
center of pressure was correlated with perceived verticality assessed by a
subjective verticality test. Together, our results suggest that veering is
related to a “sense of straight ahead” that could be shaped by vestibular inputs.