Recent experiments, with recording the activity of pyramidal tract neurons in the cat maintaining balance on the tilting platform have shown that their activity strongly correlates with tilts of the platform and Figure 9. Role of PTNs in the postural system stabilizing the dorsal side up trunk orientation in the cat A and B, proposed scheme BMS 794833 for sensorimotor processing in the postural system stabilizing the dorsal side up trunk orientation in the cat. A, the system consists of two subsystems, one for the shoulder girdle and the other for the hip girdle. They compensate for tilts of the anterior and posterior parts of the body, respectively. B, each subsystem includes two controllers, one for the left limb and one for the right limb.
Each limb controller contains a reflex mechanism driven by somatosensory input from its own limb. These local reflexes partly compensate for tilts. The limb controllers also receive AZD6482 somatosensory input from the opposite limbs. The motor responses to these crossed influences are added to the local reflexes. The forelimb controllers exert influences on the hindlimb controllers promoting their coordination. Reversed influences are much smaller. The PTNs constitute a part of each limb controller, they are primarily involved in the feedback control of their own limb. The corresponding sensory influences are shown by thick red lines. The PTNs are less involved in the coordination of activity between the two limbs within a girdle, and between the shoulder and hip girdles. The corresponding influences are shown by thin blue and green lines.
C, role of signals from the receptive field in modulation of PTNs. Three types of PTNs are shown: 1, PTN in which the receptive field input controls the activity both at rest and in the postural task, 2, PTN in which the receptive field input controls the activity only at rest the activity in the postural task is controlled by a different sensory input, 3, PTN in which the receptive field input is absent the activity in the postural task is controlled by a special sensory input. with postural corrections elicited by the tilts. This finding suggests that the motor cortex is involved in the control of body posture. In the present study, we assessed a function of the motor cortex in J Physiol 586. 1 Origin of cortical responses in postural tasks 261 this motor behaviour.
In accordance with the general structure of the trunk stabilizing system, cortical functions could be as follows. First, the motor cortex could participate in the control of an individual limb, by sending corrective motor commands based on local somatosensory inputs. In this case, PTNs should be driven by somatosensory input from their own limb. Second, themotor cortex could participate in the coordination of limbswithin a girdle. In this case, the PTNs projecting to a given limb should be driven by afferents of the contralateral limb. Third, the motor cortex could participate in the coordination of the two girdles. In this case, PTNs of a given girdle should be driven by afferents of the other girdle. We addressed this question by investigating the origin of posture related activity of PTNs. To assess a contribution of input from a given limb to the PTN activity, we used the method of varying the number of l