A long period of head-down tilt bed rest, which mimics the effects of spaceflight, results in significant changes in the functional connectivity of motor, somatosensory, and vestibular areas of the brain, according to a recent study published online this July in Neuroimage. The study found that several of these functional changes were also significantly associated with changes in sensorimotor and spatial working memory performance.
Evidence indicates that spaceflight can have a negative effect on cognition and sensorimotor functioning. For example, astronauts have been shown to perform worse on measures of locomotor function and postural stability directly after a long-duration spaceflight mission.
Prolonged exposure to a head-down tilt position during bed rest has been shown to resemble the effects of the microgravity environment experienced when in space. These effects include reduced sensory inputs to the bottom of the feet, body unloading in the axial direction and increased cephalad fluid distribution (altered distribution of fluid around the head and body).
One way of measuring changes in neural activity is by using resting state functional magnetic resonance imaging (rs-fMRI), a sensitive method for estimating correlated neural activity across different brain networks. This method is useful because the majority of the brain’s energy consumption supports neural activity that occurs while people are at rest.
The study, led by Kaitlin Cassady of the University of Michigan, investigated head-town tilt position on large-scale brain network organization and associated behavioral consequences. 17 male participants remained in bed with their heads tilted down six degrees below their feet for 70 consecutive days. Resting state functional magnetic resonance imaging (rs-fMRI) and behavioral data were obtained at seven time points: prior to, during, and after bed rest. Data was also collected from a control group of 14 participants.
The results revealed that 70 days of head-down tilt bed rest resulted in significant changes in the functional connectivity of motor, somatosensory, and vestibular areas of the brain. The researchers added, “several of these network alterations were significantly associated with changes in sensorimotor and spatial working memory performance, which suggests that neuroplasticity mechanisms may facilitate adaptation to the microgravity analog environment.”
They concluded, “The findings from this study provide novel insights into the underlying neural mechanisms and operational risks of spaceflight analog-related changes in sensorimotor performance.”
The study was titled: “Effects of a spaceflight analog environment on brain connectivity and behavior.”