Witney, Alice Geraldine; (2000) Predictive motor learning of object manipulation. Doctoral thesis (Ph.D.), University College London (United Kingdom).

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Abstract

Anticipating the consequences of our motor commands is a fundamental component of sensorimotor control. For example, when one hand pulls on an object held in the other hand, there is an anticipatory increase in grip force in the restraining hand that prevents the object from slipping. This anticipation is thought to rely on a forward internal model of the manipulated object and the motor system, enabling the prediction of the consequences of our actions. This thesis examines the learning of prediction using a virtual object paradigm. Subject's held an object in each hand whose properties were under computer control. This allowed instant changes in the behaviour of the objects being manipulated on a trial to trial basis, without providing any cues to the subject. To investigate the development of the prediction that a single object is being manipulated between the hands, the forces on each object were controlled so that the two objects were linked together, and therefore acted as a single object. Decay of prediction was examined after the linkage between the forces on the two objects was removed and they again acted as two independent objects. Prediction of single object manipulation was found to be quick to build up after the occurrence of a linkage between the objects, but slow to decay after this linkage was removed. The effect of previous experience of either linkage or independence between the objects was then examined, with as systematic effect of linkage being found on the current predictive response. When the properties of the virtual object were altered to form objects with novel spatial properties, prediction was found to be specific to the direction that the subject had previously experienced. The learning of anticipatory grip force modulation to a virtual object with novel properties was examined by the addition of a temporal delay in the linkage between action and effect. A second prediction developed coupled with the suppression of the earlier predictive response. These experimental findings have been related to the presence of forward internal models, and compared with the conditioning of a predictive motor response.

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