Abstract
How the human brain controls hand movements to carry out different tasks is still debated. The concept of synergy has been proposed to indicate functional modules that may simplify the control of hand postures by simultaneously recruiting sets of muscles and joints. However, whether and to what extent synergic hand postures are encoded as such at a cortical level remains unknown. Here, we combined kinematic, electromyography, and brain activity measures obtained by functional magnetic resonance imaging while subjects performed a variety of movements towards virtual objects. Hand postural information, encoded through kinematic synergies, were represented in cortical areas devoted to hand motor control and successfully discriminated individual grasping movements, significantly outperforming alternative somatotopic or muscle-based models. Importantly, hand postural synergies were predicted by neural activation patterns within primary motor cortex. These findings support a novel cortical organization for hand movement control and open potential applications for brain-computer interfaces and neuroprostheses.
Highlights
Unique among primates, the human hand is capable of performing a strikingly wide range of movements, characterized by a high degree of adaptability and dexterity that enables complex interactions with the environment
Scientists have debated for a long time how the human hand can attain the variety of postural configurations required to perform all the complex tasks that we encounter in activities of daily living
By combining kinematic, EMG, and brain activity measures using functional magnetic resonance imaging (fMRI), we provide the first demonstration that hand postural information encoded through kinematic synergies is represented within the
Summary
The human hand is capable of performing a strikingly wide range of movements, characterized by a high degree of adaptability and dexterity that enables complex interactions with the environment. Given that final hand postures can be described effectively as the linear combination of a small number of synergies, each one controlling a set of muscles and joints, the question arises whether kinematic or muscular hand synergies merely reflect a behavioral observation, or whether instead a synergy-based framework is grounded in the human brain as a code for the coordination of hand movements. According to the latter hypothesis, motor cortical areas and/or spinal modules may. To assess the specificity of the findings, we applied a decoding procedure to the fMRI data to predict hand postures based on patterns of fMRI activity
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