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An important issue in motor control is understanding the basic principles underlying the accomplishment of natural movements. According to optimal control theory, the problem can be stated in these terms: what cost function do we optimize to coordinate the many more degrees of freedom than necessary to fulfill a specific motor goal? This question has not(More)
Several experiments have suggested that similar physiological substrates are involved in movement execution and motor imagery, and that the same laws of movement control apply to both processes. Using a mental chronometry paradigm, we examined the effects of movement direction and added mass on the duration of actual and imagined movements. Six subjects(More)
In healthy subjects, sensorimotor after-effects of prism adaptation are known to be symmetric (they appear after using leftward and rightward optical deviations), whereas cognitive after-effects are asymmetric (they appear after using a leftward optical deviation) and rightward oriented. Sensorimotor and cognitive after-effects have been classically studied(More)
Broca's area has been considered, for over a century, as the brain centre responsible for speech production. Modern neuroimaging and neuropsychological evidence have suggested a wider functional role is played by this area. In addition to the evidence that it is involved in syntactical analysis, mathematical calculation and music processing, it has recently(More)
An important question in the literature focusing on motor control is to determine which laws drive biological limb movements. This question has prompted numerous investigations analyzing arm movements in both humans and monkeys. Many theories assume that among all possible movements the one actually performed satisfies an optimality criterion. In the(More)
Five subjects performed arm upward and downward movements at different speeds (movement duration ranged from 0.26 to 1.2 s). Fingertip paths, velocity profiles and muscle activation patterns of arm and forearm were computed. Inspection of the electromyograph (EMG) revealed that for relatively slow speeds (>0.7 s) and for both directions, only the flexor(More)
Hand reaching and bipedal equilibrium are two important functions of the human motor behavior. However, how the brain plans goal-oriented actions combining target reaching with equilibrium regulation is not yet clearly understood. An important question is whether postural control and reaching are integrated in one single module or controlled separately.(More)
How do we extrapolate the final position of hand trajectory that suddenly vanishes behind a wall? Studies showing maintenance of cortical activity after objects in motion disappear suggest that internal model of action may be recalled to reconstruct the missing part of the trajectory. Although supported by neurophysiological and brain imaging studies,(More)
Muscle synergies, i.e., invariant coordinated activations of groups of muscles, have been proposed as building blocks that the central nervous system (CNS) uses to construct the patterns of muscle activity utilized for executing movements. Several efficient dimensionality reduction algorithms that extract putative synergies from electromyographic (EMG)(More)