Transient responses to load perturbations of the forearm in a monkey with a chronic lesion in the internal capsule

Interactions of breathing with the postural regulation of the fingers

OBJECTIVES

The present study was performed to detect the interactions between breathing and the postural motor control of the fingers. A previous study revealed a scattering in the intraindividual motor responses which resembled a grouping. It is hypothesized to result from the influence of breathing.

METHODS

Torque impulses and torque steps at two intensities were applied to 17 healthy volunteers, to the II-IV fingers of their right hand. The subjects had to compensate for these additional torque loads that were triggered by a breathing-related signal and elicited at 4 different moments within a breath.

RESULTS

We demonstrated mutual influences between breathing and the regulation of finger posture. The reaction to a torque load was faster at the beginning of inspiration but more precise when the torque load was applied in mid-expiration. The motor response to torque loads was accompanied by changes in the breathing time course, particularly when the torque load was elicited during inspiration. The effects were most pronounced when torque steps were applied. The intensity of torque loads had no significant influence. Additionally, we observed that the respiratory phase-transitions often coincided with the end of the applied torque steps.

CONCLUSIONS

The results correspond well with the interactions existing between breathing and single or rhythmical movements. Further investigations of motor functions should consider this interdependence with breathing.

Force regulation is deficient in patients with parietal lesions: a system-analytic approach

By means of a quantitative system-analytic investigation strategy, the postural motor control of the fingers was evaluated, to characterise the possible deficit of force regulation in patients with parietal lesions. In spite of a normal response to short torque pulses, the parietal-lesion patients had difficulties in returning to the preload level after the application of an additional step torque load to fingers II-IV of their left or right hands. The control offset (measured 500 ms after step torque application) was significantly larger in the patient group. This deficit in the investigated patients with parietal lesions to compensate for step torque loads was not due to a paresis, but rather resulted from a disturbance in the generation of a sufficient counterforce against the applied step torque within an adequate time window and motor pattern. This distinct force-regulation deficit was found in patients with left- and right-sided parietal lesions.