The ability to move the fingers relatively independently of one another enables humans and non-human primates to manipulate diverse objects in the environment and to execute an immense variety of movements and gestures. Lesions of the motor cortex, such as those associated with stroke, give rise to persistent deficits in the ability to move the fingers individually even though the capacity to control other limb segments recovers. Such severe impairment in finger dexterity following stroke might arise because of the unusually complex coordination required among multiple muscles to produce even simple finger movements. However, little is known about how the central nervous system orchestrates ensembles of muscles to 3roduce movements of the fingers and hand. The broad goal of this project, therefore, is to identify the neural mechanisms whereby the activities of multiple muscles are coordinated in the elaboration of finger movements. Specifically, cross-correlation analysis of the firing times of motor units located in different hand muscles of human subjects will be used to estimate the extent to which coordinated activity among muscles is due to divergence of descending pathways providing common synpatic input across sets of motor nuclei.
The specific aims are designed to identify how hand muscles are assembled into functional groups for four widely different forms of synergistic activity that underlie: 1) the coordination of compartments of multi-tendoned muscles that insert upon multiple digits, 2) the coordination of separate muscles that insert upon the same digit, 3) the coordination of separate muscles that insert upon different digits yet are used habitually together for specific functions, and 4) the coordination between prime movers of digits and muscles whose activity provides joint stabilization necessary for effective digit movements. These studies will expand our knowledge of the mechanisms by which the brain controls voluntary movements and may provide important insights into the causes of motor dysfunction associated with stroke.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Study Section
Musculoskeletal Rehabilitation Sciences Study Section (MRS)
Program Officer
Chen, Daofen
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University of Arizona
Schools of Medicine
United States
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Keen, Douglas A; Chou, Li-Wei; Nordstrom, Michael A et al. (2012) Short-term synchrony in diverse motor nuclei presumed to receive different extents of direct cortical input. J Neurophysiol 108:3264-75
Fuglevand, Andrew J (2011) Mechanical properties and neural control of human hand motor units. J Physiol 589:5595-602
Johns, Richard K; Fuglevand, Andrew J (2011) Number of motor units in human abductor hallucis. Muscle Nerve 43:895-6
Marcus, Patrick L; Fuglevand, Andrew J (2009) Perception of electrical and mechanical stimulation of the skin: implications for electrotactile feedback. J Neural Eng 6:066008
Anderson, Chad V; Fuglevand, Andrew J (2008) Probability-based prediction of activity in multiple arm muscles: implications for functional electrical stimulation. J Neurophysiol 100:482-94
Waller, B M; Parr, L A; Gothard, K M et al. (2008) Mapping the contribution of single muscles to facial movements in the rhesus macaque. Physiol Behav 95:93-100
McIsaac, Tara L; Fuglevand, Andrew J (2008) Common synaptic input across motor nuclei supplying intrinsic muscles involved in the precision grip. Exp Brain Res 188:159-64
McIsaac, Tara L; Fuglevand, Andrew J (2007) Motor-unit synchrony within and across compartments of the human flexor digitorum superficialis. J Neurophysiol 97:550-6
Bailey, E Fiona; Rice, Amber D; Fuglevand, Andrew J (2007) Firing patterns of human genioglossus motor units during voluntary tongue movement. J Neurophysiol 97:933-6
Fuglevand, Andrew J; Dutoit, Andrea P; Johns, Richard K et al. (2006) Evaluation of plateau-potential-mediated 'warm up' in human motor units. J Physiol 571:683-93

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