A new MRI subject position to explore simultaneous BOLD oscillations of the brain and the body

•Arm-over-head MRI position was developed to study EPI BOLD in and outside the brain.•Simultaneous FMRI of the brain and limb were collected with decent SNR.•Motor imagery tasks revealed ICA components and FC across the brain and limb.•Existence of extensive whole-body functional network(s) is rational and possible. Anatomically and physiologically, there is strong relationship between the brain and body. A new MRI platform covering both the brain and the limb would be beneficial for a more thorough understanding of the brain-body interactions. A new arm-over-head (AOH) position was developed to collect MRI of the brain and one arm simultaneously. Subject’s tolerability and SNR of both the brain and limb under a serial of seven different TR (250–3000 ms) were tested. Then, blocked motor imagery tasks were performed to test the possible brain-body oscillations. The new MRI position provided structural images with good quality, and the AOH position had the best SNR under TR 3000 ms (p = 0.03 for the brain; p = 0.064 for the limb). Then, by using both hypothesis-free independent component analysis (ICA) and a priori seed-based functional connectivity (FC) analysis, it is demonstrated during motionless motor imagery tasks there existed possible brain-body BOLD oscillations connecting especially arm flexors to default mode, vision, and sensorimotor networks. The FC appeared at network density as low as 5%. We have developed a new MRI subject position to explore the possibilities of more extensive neuronal and physiological networks. The results of this preliminary experiment indicate that functional brain networks might extend outside the brain. A bottom-up circulatory effect might explain this phenomenon. Nonetheless, considering the mechanism of neural top-down control and the nature of complex brain networks, the existence of a more extensive whole-body functional network is rational and possible.