ÌÇÐÄTV

 '9.4T fMRI and feMRI rat model of injury to nerves of the brachial plexus'

Cubic voxels as small as 0.3 mm can be used for functional, as well as functional connectivity, magnetic resonance imaging (fMRI; fcMRI) in rat brain at 9.4T.  Thus, cortical layer specific studies with cortical column resolution are feasible.  In a first project, the four major nerves of the brachial plexus (ulnar, median, radial, and musculocutaneous) were individually stimulated at varying currents and frequencies using surgically implanted electrodes.  Both motor and sensory areas of the ratunculus were mapped.  Functional connectivity studies were carried out in resting brain using reference waveforms derived from regions that were revealed by the electrical stimulation protocol. Results are consistent with known motor systems of the rat brain. In a second study, the eight digits of the forepaws were individually stimulated.  It was demonstrated that representations of the individual digits can be resolved by both fMRI and fcMRI methods.  In a third study, the four major nerves of the forearm were transected and functional connectivity studies carried out after two weeks.  Interhemispheric connectivity was severely decreased, but patterns of intrahemispheric connectivities were largely unaltered.  This is believed to be new information that is obtainable by fcMRI methods but not by fMRI methods.  We seek to develop a rat model of central nervous system (CNS) response to peripheral nervous system (PNS) injury and repair that can be translated to humans for development of improved surgical and rehabilitation protocols.