Magnetic resonance imaging of neuronal
function in the human spinal cord has been
developed to the point that it can accurately
demonstrate activity in response to a variety of sensory stimuli, painful
stimuli, or motor tasks. It has also been demonstrated to detect
changes as a result of traumatic injury and multiple
Methods have been developed
to overcome (or at least reduce) the key challenges of
1) magnetic field differences in different materials
(bone, tissue, air), 2) movement caused by the heart
beat and breathing, and 3) the small physical
dimensions of the spinal cord.
Software has been developed specifically for
spinal cord and brainstem fMRI analysis. This includes methods
to reduce image artifacts, correct for movement, carry
out the analysis, and convert the results into a
spatially normalized form that is the same for every
person. Group analysis to characterize consistent features of how
spinal cord and brainstem function are affected by
injury, or disease, or normal differences in responses to different
sensations can also be carried out. In
addition, software has been developed to carry out analyses
to identify connectivity between regions that are working
as part of a network.
Example of the most sophisticated connectivity methods that have been applied to the spinal cord and brainstem to date.
This figure shows the connectivity between regions in response to two different timing patterns of hot thermal stimulation of the hand. The "block" stimulus is
a constant heat at 45 C, whereas the "stepwise" gradually increases in steps to 45 C, and produces a different sensation, with more of the transient response
to changes in temperature. The connectivity was calculated using structural equation modeling (SEM).