Detecting postural responses to sinusoidal sensory inputs: a statistical approach.

A common way for understanding sensory integration in postural control is to provide sinusoidal perturbations to the sensory systems involved in balance. However, not all subjects exhibit a response to the perturbation. Determining whether or not a response has occurred is usually done qualitatively, e.g., by visual inspection of the power spectrum. In this paper, we present the application of a statistical test for quantifying whether or not a postural sway response is present. The test uses an F-statistic for determining if there is significant power in postural sway data at the stimulus frequency. In order to describe the application of this method, 20 subjects viewed sinusoidal anterior-posterior (A-P) optic flow at 0.1 and 0.25 Hz, while their A-P head translation was measured. The test showed that significant postural responses were detected at the stimulus frequency in 12/20 subjects at 0.1 Hz and 13/20 subjects at 0.25 Hz.