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It is commonly believed that cerebrospinal fluid (CSF) movement is facilitated by blood vessel wall movements (i.e., hemodynamic oscillations) in the brain. A coherent pattern of low frequency hemodynamic oscillations and CSF movement was recently found during non-rapid eye movement (NREM) sleep via functional MRI. This finding raises other fundamental questions: 1) the explanation of coupling between hemodynamic oscillations and CSF movement from fMRI signals; 2) the existence of the coupling during wakefulness; 3) the direction of CSF movement. In this resting state fMRI study, we proposed a mechanical model to explain the coupling between hemodynamics and CSF movement through the lens of fMRI. Time delays between CSF movement and global hemodynamics were calculated. The observed delays between hemodynamics and CSF movement match those predicted by the model. Moreover, by conducting separate fMRI scans of the brain and neck, we confirmed the low frequency CSF movement at the fourth ventricle is bidirectional. Our finding also demonstrates that CSF movement is facilitated by changes in cerebral blood volume mainly in the low frequency range, even when the individual is awake. [ABSTRACT FROM AUTHOR]

Infant social-communicative behavior, such as gaze to the face of an interactive partner, is an important early developmental skill. Children with autism spectrum disorder exhibit atypicalities in social-communicative behavior, including gaze and eye contact. Behavioral differences in infancy may serve as early markers of autism spectrum disorder and help identify individuals at highest risk for developing the disorder. Researchers often assess social-communicative behavior in a single interactive context, such as during assessment with an unfamiliar examiner or play with a parent. Understanding whether infant behavior is consistent across such contexts is important for evaluating the validity of experimental paradigms and the generalizability of findings from one interactive context/partner to another. We examined infant gaze to the face of a social partner at 6, 9, and 12 months of age in infants who were later diagnosed with autism spectrum disorder, as well as low- and high-risk infants without autism spectrum disorder outcomes, across two interactive contexts: structured testing with an unfamiliar examiner and semi-structured play with a parent. By 9 months, infant gaze behavior was significantly associated between the two contexts. By 12 months, infants without autism spectrum disorder outcomes exhibited higher mean rates of gaze to faces during parent–child play than Mullen testing, while the gaze behavior of the autism spectrum disorder group did not differ by context—suggesting that infants developing autism spectrum disorder may be less sensitive to context or interactive partner. Findings support the validity of assessing infant social-communicative behavior during structured laboratory settings and suggest that infant behavior exhibits consistency across settings and interactive partners. [ABSTRACT FROM AUTHOR]