Co-Activation Patterns in Neonates using High-Density Diffuse Optical Tomography: Insights into Early Dynamic Functional Connectivity
Dynamic functional connectivity (FC) in neonates is a growing area of interest due to the developmental significance of early functional networks. There are several emerging techniques to measure dynamic FC, adding new perspectives to well-studied static FC networks. Recent dynamic FC studies suggest that adult resting state networks are driven by key moments of dynamic activity rather than sustained correlations. Co-activation pattern (CAP) analysis leverages this theory, clustering high-activity frames to identify recurring configurations of significant activity. High-density diffuse optical tomography (HD-DOT) is an infant-friendly modality that measures hemodynamic changes in the cortex. HD-DOT has been used to investigate static FC in term-aged infants. The CAP approach is a promising avenue to examine dynamic FC in neonates, but it is yet untested in neonatal HD-DOT. This study validates the CAP approach for neonatal HD-DOT and presents novel decompositions of neonate FC networks. HD-DOT data were acquired from a cohort of sleeping term newborns at the Rosie Hospital, Cambridge UK (n = 44, postmenstrual age = 40+3 (range: 38+2 - 42+6) weeks). The top 15% of seed-selected frames were clustered using the K-means algorithm for three regions of interest (ROIs: frontal, central, and parietal) to identify significant seed-associated patterns of co-activation or co-deactivation. These patterns (CAPs) were characterized using four metrics: consistency, fractional occupancy, dwell time, and transition likelihood. Distinct CAPs were identified for frontal, central, and parietal regions of interest. These CAPs had high consistency scores, validating the efficacy of the CAP methodology for newborn HD-DOT. The CAP decomposition revealed significant patterns obscured by static analysis. Several neonate CAPs illustrate frontoparietal activity, potentially reflecting early default mode network activity, which is immature and modular for the first year after birth. This work demonstrates the utility of CAP analysis with newborn HD-DOT and provides new insight into brain dynamics of early resting state networks.