Fig. 4

Typical SDP of a PD patient’s COP signal: (A) PD patient’s stabilogram; (B) PD patient’s sway density curve. In (A), R (3 mm) was the given radius within which the COP trajectory could fall instantaneously at each time interval. SDP = sway density plot, EO = Eye Open, ML = medial-lateral, AP = anterior-posterior, x = ML, y = AP, COP = center of pressure