Effects of Added Vestibular Noise on Blindfolded Locomotor Veering

BACKGROUND: Nearly every fundamentally healthy human, regardless of fitness, age, or gender is incapable of walking in a perfectly straight line when visual information is removed. This is known as veering. Many different potential causes have been examined, but the most persuasive explanation is that without visual input, sensory interference (or noise) accumulates and causes random motor output errors. OBJECTIVE: The aim of this study was to examine veering behavior during blindfolded walking when added vestibular noise (vibration) was applied to the skull at select locations. METHODS: A handheld massager attached at the top of the head or over one ear (dominant eye side for half the sample and non-dominant eye side for half the sample) was worn during all trials and activated for half of the efforts. Fundamentally healthy participants (n=16) completed 4 trials under each of 4 experimental combinations using a balanced Latin Square block testing sequence. Effects of the presence and location of applied vibration on veering direction and magnitude were evaluated via repeated measures 2x2 ANOVA (α=0.05). RESULTS: Location and noise effects were observed for absolute veering; a 0.72° increase when located on the side and a 1.55° increase with noise. For directional veering, a significant interaction effect was identified: when noise was applied over the ear, veering was biased toward that side by 1.14°. Directional veer angles for all other combinations were functionally zero. CONCLUSION: Sensory interference caused by the vibrations of the massager increased both absolute veering and the direction of veering and was viewed as support for the accumulated sensory noise theory.