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Abstract

Since the first application of functional connectivity (FC) in examining brain functional architecture, it has pushed a huge step forward in the field and deepened our understanding of how the brain is organized functionally. As a measure of temporal correspondence between neural elements, FC is usually calculated during tasks or task-free sessions. Task FC is often interpreted as reflecting the degree to which specific neural network are engaged to support task performance, whereas task-free FC is regarded as a reflection of general state of the brain including the network maturity and dysfunction. While both approaches capture certain individual characteristics, a key question remains — to what extent do these two measures converge, and in what ways might they diverge? Answering this question is important as it may provide valuable insights into the developmental bases of FC and how network maturity and network function interrelate. Current study focuses on 8-month-old infants, who are at a critical stage of neural development, offering a precious opportunity to examine the relationship between task and task-free FC. Two separate studies were conducted for each participant. The first visit is a task-free session and infants were presented with a video called “Inscapes”, which features constant transformations of complex three-dimensional graphics, and no instructions were imposed. The second visit is a sequence learning task adapted from Baek et al. (2022) which includes two conditions (predictable and unpredictable sequence condition) and the frontoparietal network (FPN) was found to be actively engaged. Functional infrared spectroscopy designed to cover FPN was applied in both visits of the study for examining brain activities. The hypothesis is that infants who showed larger FC difference between two conditions in task (i.e., better cognitive ability) would have stronger task-free FC (i.e., higher network maturity). The results, however, showed an opposite direction — infants with larger FC difference have weaker task-free FC. Possible explanations include the failure of replicating the previous finding of significant FPN engagement in the task session, the potential influence of demographic factors such as multilingualism, and the high individual variability of anatomical localization of FPN. Further explanations and future directions are discussed.