Our findings were consistent across both the HCP-D and HCP-YA datasets. Additionally, we replicated these results in an independent youth cohort collected by our lab over the past two years, further demonstrating the robustness and generalizability of our findings 9/n.

We found that the connectional variability axis slope positively correlated with higher-order cognitive performance, controlling for age. This effect was driven by greater individual variability in association connections among higher-cognitive individuals 8/n.

To assess the development of the FC variability axis, we calculated its slope. During youth, the variability axis slope declines with age, primarily driven by reduced FC variability in connections between association networks 7/n.

Using diffusion MRI to construct individual structural connectomes, we find that the connectional axis of FC variability aligns with the spatial pattern of individual variability in structural communicability across edges, suggesting a potential structural basis 6/n.

Next, we ranked FC variability across all 21 within- and between-network connections to define the “connectional variability axis.” Association-association (A-A) connections occupy the top of the axis, while sensorimotor-association (S-A) connections anchor the base 5/n.

Ranking FC variability within and between networks revealed an axis of decreasing variability from within-network to between-network edges. For example, in the DMN, variability declines from edges linking association areas to those connecting with sensorimotor regions 4/n.

We analyzed edge-level FC variability and summarized within- and between-network averages using the Yeo atlas. FC variability was heterogeneously distributed across connectome edges and consistent between datasets 3/n.

Regional FC variability is heterogeneously distributed across the cortex, decreasing progressively from higher-order association to primary sensorimotor cortices (Mueller et al., 2013, Neuron). However, edge-level details remain unclear 1/n.

Excited to share our work “Connectional axis of individual functional variability: Patterns, structural correlates, and relevance for development and cognition,” now out at @pnas.org www.pnas.org/doi/10.1073/....