Resting state networks in human cervical spinal cord observed with fMRI.

It has been reported that spontaneous fluctuations of blood oxygen level dependent (BOLD) signals can be detected in human brain and constitute resting state networks. It has not been reported whether resting state networks also exist in human spinal cord. In the present study, we investigate spontaneous BOLD signal changes in human cervical spinal cord during resting state. fMRI data were analyzed with independent component analysis and SPM software package. Acceptable reproducibility of spatial maps of BOLD signal changes was found across sessions, with the highest correlation values ranging from 0.18 to 0.44. The dominant frequency of signal changes from independent components with the highest correlation values was approximately the frequency range of the respiratory circle. Activities of spinal motor neurons innervating the scalenes were considered as a major factor in the production of BOLD signal fluctuations were observed in this study. Our findings suggest that BOLD fMRI can be applied to study the features of low-frequency rhythmic activities and corresponding mechanisms in the spinal cord during resting state.