FMRI And Electrophysiological Studies On The Ross-hemispherical Brain Plasticity After Contralateral C7 Transfer

Objective By comparing BOLD-fMRI with electrophysiologicaltechniques ,to evaluate the feasibility of functional MRI to localize the ratsensorimotor representations of forepaw and to determine optimum parameters.Materials and Methods Sixteen Sprague-Dawley female rats were performedfunctional MRI while varying effective echo time from 40 to 60 msec in 10-msecincrements .Stimulus sequences were divided into six 30-second segments thatalternated between resting and stimulated states. A single BOLD measurement wasmade for each animal .The number of activated voxels and the BOLD responseamplitude in the maximally responding activated voxels were used for analysis. AfterfMRI examination, all the rats were received electrophysiological studies(intracortical microstimulation and somatosensory evoked potentials recording) .Results The center of the main cortical representations of the forepaw were situated3-6 mm posterior to frontal pole and 1.5-4.5 mm lateral to the midline, contralateralto the stimulated forepaw . The optimal effective echo time for our BOLD activationmodel was 50 msec, which produced the maximal BOLD response amplitude andmaximal number of activated voxels , its activated volume was 10.99 mm3±3.5. Thehighly localized area of activation by fMRI is almost consistent with theelectrophysiological area ,the accuracy of location is 90.6%. Conclusion fMRI is apromising and no injury method to detect the rat sensorimotor cortex during forepawstimulation. It should prove useful for testing and developing new human functionalMRI techniques.