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CURRENT RESEARCH NEURAL CONTROL OF MULTI-JOINT LIMB MOVEMENT IN THE CAT AND IN HUMANS We investigate the neural mechanism underlying the control of voluntary movements in human subjects. In particular, our work analyzes the execution of aimed movements and examines the implicit and explicit aspects of learning accuracy and complex motor sequences. Psychophysical studies of limb kinematics (describing trajectories) and dynamics (describing torques acting at the joints) are carried out in conjunction with neuroimaging analyses of regional cerebral blood flow with H215O. The first aim of our work is to determine how neural mechanisms simplify the computational task of controlling the complex biomechanical system that is the moving limb. This investigation is carried out in normal subjects and patients with loss of large afferent-caliber fibers. The study verifies the role of proprioceptive information in movement execution and in learning of muscle coordination in novel experimental conditions. The second set of studies addresses the translation of stimulus information into movement extent and direction. Our work shows that programming of reaching movements involves a coordinate transformation in which the target location specifies extent and direction of the intended movement in a polar system with origin at the starting point. We have shown the extent and direction are processed by independent parallel channels. We are currently studying how subjects adapt to novel visual correspondences and learn new visuomotor transformation involving either direction or extent. Third, we are characterizing the processes involved in learning of complex motor sequences and defining their neural bases with psychophysical and imaging techniques. To investigate the role of basal ganglia in learning processes, the last two sets of experiments are performed in both normal subjects and patients with Parkinson's disease. SELECTED PUBLICATIONS Scheidt, R.A., and Ghez, C. 2007. Separate adaptive mechanisms for controlling trajectory and final position in reaching. J. Neurophysiol. 98:3600-3613. Krakauer, J.W., Ghez, C., and Ghilardi, M.F. 2005. Adaptation to visuomotor transformations: consolidation, interference, and forgetting. J Neurosci. 25:473-8. Krakauer, J.W., Ghilardi, M.F., Mentis, M., Barnes, A., Veytsman, M., Eidelberg, and D., Ghez, C. 2004. Differential cortical and subcortical activations in learning rotations and gains for reaching: a PET study. J Neurophysiol. 91:924-33. Ghilardi, M.F., Carbon, M., Silvestri, G., Dhawan, V., Tagliati, M., Bressman, S., Ghez, C., and Eidelberg, D. 2003. Impaired sequence learning in carriers of the DYT1 dystonia mutation. Ann Neurol. 54:102-9. Mentis, M.J., Dhawan, V., Nakamura, T., Ghilardi, M.F., Feigin, A., Edwards, C., Ghez, C., and Eidelberg, D. 2003. Enhancement of brain activation during trial-and-error sequence learning in early PD. Neurology. 60:612-9. Fukuda, M., Ghilardi, M.F., Carbon, M., Dhawan, V., Ma, Y., Feigin, A., Mentis, M.J., Ghez, C., and Eidelberg, D. 2002. Pallidal stimulation for parkinsonism: improved brain activation during sequence learning. Ann Neurol. 52:144-52. Feigin, A., Ghilardi, M.F., Fukuda, M., Mentis, M.J., Dhawan, V., Barnes, A., Ghez, C.P., and Eidelberg, D. 2002. Effects of levodopa infusion on motor activation responses in Parkinson's disease. Neurology. 59:220-6. Fukuda, M., Mentis, M., Ghilardi, M.F., Dhawan, V., Antonini, A., Hammerstad, J., Lozano, A.M., Lang, A., Lyons, K., Koller, W., Ghez, C., and Eidelberg, D. 2001. Functional correlates of pallidal stimulation for Parkinson's disease. Ann Neurol. 49:155-64. Nakamura T, Ghilardi MF, Mentis M, Dhawan V, Fukuda M, Hacking A, Moeller JR, Ghez C, Eidelberg D. (2001). Functional networks in motor sequence learning: abnormal topographies in Parkinson's disease. Hum Brain Mapp. 12:42-60. Cooper, S.E., Martin, J.H., and Ghez, C. 2000. Effects of inactivation of the anterior interpositus nucleus on the kinematic and dynamic control of multijoint movement. J Neurophysiol. 84:1988-2000. Ghilardi, M., Ghez, C., Dhawan, V., Moeller, J., Mentis, M., Nakamura, T., Antonini, A., and Eidelberg, D. 2000. Patterns of regional brain activation associated with different forms of motor learning. Brain Res. 871:127-45. Martin, J.H., Cooper, S.E., Hacking, A., and Ghez, C. 2000. Differential effects of deep cerebellar nuclei inactivation on reaching and adaptive control. J Neurophysiol. 83:1886-99. Ghez, C., Favilla, M., Ghilardi, M.F., Gordon, J., Bermejo, R., and Paullman, S. 1997. Discrete and continuous planning of hand movements and isometric force trajectories. Exp. Brain Research 115:217-233 Virji-Babul, N., Sainburg, R.L., Huang, H., and Ghez, C. 1997. Rate of learning novel limb dynamics depends on the nature of feedback signals. Soc. Neurosci. Abstract, 85.7:002 Krakauer, J.W., Pine, Z.M., Ghuilardi, M.F., Huang, H., and Ghez, C. 1997. Learning a rotated reference frame requires moving in multiple directions and differs with the joint system used. Soc. Neurosci. Abstract, 85.8:202 Pine, Z.M., Krakauer, J.W., Gordon, J., and Ghez, C. 1996. "Learning of scaling factors and reference axes for reaching movements". Neuroreport 7:2357-2361 Ghilard, M.F., Gordon, J., and Ghez, C. 1995. Learning a visuomotor transformation in a local area of workspace produces directional biases in other areas. J. Neurophysiol. 73.6:2535-2539 |
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