Are interlimb interactions disturbed in patients with Parkinson’s disease? A study under unloading conditions

Abstract

During natural human locomotion neural connections characteristic for the control of quadrupedal walking are activated. The degree of interaction between the neural networks generating rhythmic movements of the upper and lower extremities, depends on the tonic state of each of these networks, adjustable by motor command in the brain. The distortion of such command in patients with Parkinson's disease (PD) may lead to disturbance of interlimb interactions. In conditions of arms and legs unloading in 17 patients with PD and 16 healthy subjects investigated the effect of limb movement of one girdle on the parameters of motor activity of the limbs of the other girdle in their combined cyclic movements. In patients the weakening of influences of active or passive arm movements, and active movements of the distal parts of the arms on voluntary leg movements was shown, while in healthy subjects the effect of arm movements on the parameters of voluntary movements was significant. The effect of arm movements on the possibility of involuntary activation of air- stepping by vibratory stimulation of the leg muscles in patients was absent, while in healthy subjects the motor activity of the arms increased the opportunity of involuntary rhythm activation. The differences in the influence of leg movements to the rhythmic movement of the upper extremities in patients and healthy subjects were revealed. The medication exhibited interlimb interaction, but it was insufficient for normalization of the state of neural networks in patients. It is concluded that in patients with PD, neural networks generating stepping rhythm are in a state of heightened tonic activity. This does not allow not only activating involuntary rhythmic movements, but also showing facilitation effect with arms to legs.