THE ROLE OF THE PLANTAR MECHANORECEPTOR IN EQUILIBRIUM CONTROL

Several methods for observing body equilibrium or postural reflexes have been developed recently: the statokinesimeter, three-point suspension, the pedoscope, and gravigoniometry of the sway of the center of gravity.'-4 Studies utilizing these methods are now actively under way. In the past several years, we have engaged in studies of body sway in order to determine how it is controlled. We have reported that body sway in a dark field is different from that in a bright field with eyes open and eyes closed. It is more valuable to observe labyrinth disturbances in a dark field.5 It also has been reported that breathing and position of the feet have considerable influence on the test results.' Many other factors besides these control body sway. When a person stands on two feet, he feels weight resistance on the plantar surface, but little is known yet about how plantar mechanoreceptors influence body sway. Adrian stated on the basis of his electrophysiological experimentation that the plantar and palmar sensory receptors have slower adaptation than do other sensory ~rgans.~.'This agrees well with the idea that the plantar and palmar sensory receptors should be slow in ada~ting.'~.'' We developed a method for adding weight resistance to the plantar mechanoreceptors, and have studied body-sway control mechanisms. These findings are reported in this paper.