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Abstract

When reaching to grasp, we coordinate how we preshape the hand with how we move it. The temporal and spatial coordination of transport and grasp components during reach-to-grasp behavior has been studied extensively in psychophysics experiments (M. Jeannerod 1984; Haggard and Wing 1995). Little is known, however, on the role of neocortex in generating, driving, or modulating the coordination of such behavior. The results discussed in this thesis attempt to answer the question: how do neural ensembles in the primary motor cortex functionally interact to produce coordinated behavior? In the first study, we examined the interactions between reach- and grasp-related neuronal ensembles while monkeys reached-to-grasp a variety of different objects in different locations. By describing the dynamics of these two ensembles as trajectories in a low-dimensional state space, we examined their coupling in time. The development of this coordination has been studied in infants and children (Claes von Hofsten 1984; Kuhtz-Buschbeck, Stolze, Jöhnk, et al. 1998; Wimmers et al. 1998). As children age, their inter-joint coordination becomes more stereotyped (Claes von Hofsten 1984; Kuhtz-Buschbeck, Stolze, Jöhnk, et al. 1998). Less is known about the role of motor cortex in developing coordinated reach-to-grasp. Additionally, studies have shown that after amputation, the cortical area previously involved in the control of the lost limb undergoes reorganization (J. N. Sanes et al. 1988; J. N. Sanes, Suner, and Donoghue 1990; Schieber and Deuel 1997; Wu and Kaas 1999; Qi, Stepniewska, and Kaas 2000), but limited work has gone towards developing BMIs that use neurons that are not tuned for kinetic or kinematic features. In the second study, we probed the emergence of coordinated reach-to-grasp in macaques that were being taught to cortically control a robotic arm through operant conditioning, and probed the neural correlates of this emergence.

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