Effect of neck and trunk rotation speeds on cerebral cortex activity and standing postural stability: a functional near-infrared spectroscopy study

[Purpose] The aim of the present study was to determine whether different neck and trunk rotation speeds influence standing postural stability or frontal and temporal cortical activity during rotation in healthy young adults. [Subjects and Methods] Twelve healthy volunteers participated in this study. A custom turn-table operated by one of the experimenters was placed on a platform to assess postural perturbation. Subjects were asked to stand barefoot on the turn-table in an upright position with their feet together, and measurements were obtained during high- and low-speed rotations. Postural stability was tested using a force platform and a head sensor. Cerebral cortex activity was measured using functional near-infrared spectroscopy. Brain activity, center of pressure, and head perturbation were measured simultaneously for each subject. [Results] Significant differences were found in the center of pressure and the head angular velocity between high- and low-speed rotations. However, compared to baseline, oxygenated hemoglobin levels were not significantly different during high- or low-speed rotations. [Conclusion] Automatic postural responses to neck and trunk rotation while standing did not significantly activate the cerebral cortex. Therefore, the response to stimuli from the feet may be controlled by the spinal reflex rather than the cerebral cortex.