ORGANIZING SENSORY INFORMATION FOR POSTURAL CONTROL IN ALTERED SENSORY ENVIRONMENTS

Healthy human subjects can maintain adequate balance despite distorted somatosensory or visual feedback or vestibular feedback distorted by a peripheral vestibular disorder. Although it is not precisely known h ow this sensorimotor integration task is achieved, the nervous system coordinates information from multiple sensory systems to produce motor commands differently in different sensory environments. These differe nt ways of coordinating sensory information and motor commands can be thought of as ''sensorimotor states''. The way the nervous system dist ributes the monitoring of postural sway among states is analysed in th is paper as a logical structure of transitions between states. The for m of the transition structure is specified and distinguished from a fi nite state machine. The hypothesis that the nervous system could use a transition structure to maintain balance is tested by developing tran sition structures which are consistent with a set of experimental obse rvations of postural control in healthy subjects and three groups of p atients with peripheral vestibular disease. (C) 1996 Academic Press Li mited