While both visual and somatosensory feedback are likely to play a critical role in the learning of novel dynamics, several previous studies on motor learning have shown that adaptation to stable dynamics is possible even when subjects are provided only with delayed visual feedback of the trajectory, deprived of online visual feedback of their hand position during movements, or are congenitally blind. Evidence suggests that in stable dynamics an internal model of the environmental forces is acquired, while in unstable or unpredictable dynamics impedance control may be used to selectively modify endpoint impedance through the co-activation of specific muscle pairs, –. While succeeding in stable dynamics requires the production of counteracting interaction forces through the feed-forward motor command, the unpredictability brought by unstable interactions requires modifying the limb impedance. However, the types of compensation required in stable and unstable interactions are different, and learning these two kinds of interactions may involve distinct processes. It has been shown that people are able to learn the novel dynamics of both stable environments as well as unstable or unpredictable environments –.
What sensory signals actually drive this adaptation? The question arises as to whether all of these modes of sensory feedback are necessary or important for learning an internal model of these novel dynamics.
By practicing and using the combined visual, proprioceptive and contextual feedback information available to him, the person can gradually learn to adjust the necessary forces or joint torques produced by his arms in order to perform the movement correctly.
#VISUAL NOVEL READER CHANGING MOUSE CURSOR HOW TO#
The person therefore must learn how to compensate for these new dynamics in order to be able to effectively use the tool. These effects change the required muscle activation patterns throughout the entire system in order to move the tool appropriately. The tool also drastically modifies the interaction with the environment, which can become unstable. For example, if a person picks up a screwdriver for the first time, the entire system, composed of the person, their limbs and the screwdriver, now has altered dynamics due to the added mass and inertia of the tool. In addition to visual information, muscle spindles, Golgi tendon organs, joint and tactile sensors provide proprioceptive and tactile information about the person's body and any object which is now coupled to the body. Visual information provides contextual cues, trajectory feedback, and information about the appearance of objects in the environment. When learning a novel task, an array of sensory modalities and information could be used. The performance and learning of novel reaching tasks requires people to integrate multi-modal sensory information about the new environment in order to learn to apply the appropriate forces necessary to compensate for the novel dynamics. Similarly, vision and proprioception contribute differently to different components of the motor command. The weighting of this integration may vary depending on the task. In order to perform motor tasks, the central nervous system integrates multiple modes of sensory information –, particularly vision and proprioception.
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