The role of proprioceptive information in programming of anticipatory postural components of voluntary movements

Anticipatory components of the EMG activity of the postural muscles during a voluntary movement were analyzed to find out how the CNS regulates these components in response to changes in the movement parameters and what information is used for programming these components. The fast lift of an arm in an erect posture was used as a model. The parameters of the movement were modified by varying weights held in the hand (0.5, 1.0, and 1.5 kg) and the preliminary information on these weights: lifting the hand holding a weight and lifting an unknown weight from a support in the absence of information on its value or after receiving verbal information on it. Our experiments showed that the program of maintaining an erect posture while performing a fast voluntary lift of the arm involves anticipatory adjustments of postural muscles (the soleus muscle, biceps muscle of the thigh, and sacrospinal muscle) using information on the parameters of the movement to be performed. For all these muscles, the anticipation time did not depend on either experimental conditions or the velocity of lifting the arm. The duration of the activity and its amount had different dependences on the lifted weight. The parameters of inhibition of the soleus muscle did not depend on the lifted weight, the activity of the biceps muscle of the thigh was mainly regulated by varying its amplitude, and the regulation of the sacrospinal muscle involved both amplitude and duration changes. It was shown that the adjustment of anticipatory movement components can be only based on proprioceptive rather than verbal (conscious) information.