Head movement measurement: An alternative method for posturography studies.

The present study evaluated the measurement of head movements as a valid method for postural emotional studies using the comparison of simultaneous recording of center of pressure (COP) sway as criterion. Thirty female students viewed a set of 12 pleasant, 12 unpleasant and 12 neutral pictures from the International Affective Picture System, repeated twice, using a block presentation procedure while standing on a force platform (AMTI AccuSway). Head movements were recorded using a webcam (©KPC139E) located in the ceiling in line with the force platform and a light-emitting diode (LED) placed on the top of the head. Open source software (CvMob 3.1) was used to process the data. High indices of correlation and coherence between head and COP sway were observed. In addition, pleasant pictures, compared with unpleasant pictures, elicited greater body sway in the anterior-posterior axis, suggesting an approach response to appetitive stimuli. Thus, the measurement of head movement can be an alternative or complementary method to recording COP for studying human postural changes.