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The viscoelastic properties of the human arm were measured by means of short force perturbations during fast reaching movements in two orthogonal directions. A linear spring model with time delay described the neuromuscular system of the human arm. The obtained viscoelastic parameters ensured movement stability in spite of the time delay of 50 ms. The(More)
It has been widely claimed that linear models of the neuromuscular apparatus give very inaccurate approximations of human arm reaching movements. The present paper examines this claim by quantifying the contributions of the various non-linear effects of muscle force generation on the accuracy of linear approximation. We performed computer simulations of a(More)
Human subjects sitting in a chair were asked to maintain their right forearm in a horizontal position in half supination. The forearm was loaded with a constant weight of one kilogram. Vertical force at the wrist level, angular position of the elbow and EMG activity of biceps, brachio-radialis and triceps muscles were recorded. Unloading was tested under(More)
The role of the sensorimotor cortex in the postural adjustments associated with conditioned paw lifting movements was investigated in the cat. Cats were trained to stand quietly on four strain gauge equipped platforms and to perform a lift-off movement with one forelimb when a conditioned tone was presented. The parameters recorded were the vertical forces(More)
The acquisition of co-ordination between posture and movement was investigated in human subjects performing a load lifting task. Sitting subjects held their left (postural) forearm in a horizontal position while supporting a 1 kg load via an electromagnet. Perturbation of the postural forearm position consisted of the load release triggered either by the(More)
In alert albino rabbits, the cerebellar flocculus was mapped for the effect of its local stimulation upon eye movements. Stimulation through a glass pipette electrode placed in a relatively rostral area induced abduction of the ipsilateral eye. That in a relatively caudal area resulted in a downward movement of the ipsilateral eye, accompanied by an upward(More)
A bimanual loading task was studied in eight right-handed normal subjects and nine hemiparetic patients in order to detect anticipatory adjustments and to analyse the reflex and voluntary, responses induced by the perturbation. The left forearm (or the impaired side in patients) was flexed at approximately 90 degrees and free to rotate in a vertical(More)
The postural response to an unexpected drop of either hindlimb platform was studied in the freely standing cat. The vertical forces, the forelimb electromyographic (EMG) activities and the movement of the trunk were analysed. A stereotyped diagonal pattern of support was observed. The imposed unloading of one hindlimb was followed by unloading of the(More)