Motor cortical organization has commonly been conceived as somatotopically ordered, with single body parts controlled from individual patches of cortical tissue. An opposing viewpoint suggests that motor cortex has a distnbuted, adaptive, and dynamic organi zation that underlies movement planning, performance, adaptation, and learning. Con verging evidence from anatomic, neurophysiologic, and functional neuroimaging sources indicates that the arm area of motor cortical areas in monkeys and humans has multiple, interconnected sites that ostensibly contribute to controlling various parts of the arm. These representations can exhibit rapid and sometimes enduring modifications following injury, changes in somatic sensory input, and motor learning. Activity-dependent changes in the intrinsic motor cortical network of horizontal and vertical connections coupled with ascending thalamic and corticocortical inputs could provide a substrate for dynamic mod ulation of motor cortex functional representations. NEUROSCIENTIST 3:158-165, 1997
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