# The effective connectome over a century of human life

## TL;DR

This study maps how brain networks develop from birth to 100 years old, showing key changes in early life and a pattern governed by inhibitory connections.

## Contribution

The study introduces a lifespan analysis of directed brain connectivity, revealing a critical early plasticity window and inhibitory-driven development patterns.

## Key findings

- Effective connectivity follows an inverted U-shape with maturation at ~9 years, earlier than functional connectivity.
- Regional EC strength is more variable in early development, indicating a critical plasticity window.
- Inhibitory nodal EC governs the sensorimotor-association gradient during development.

## Abstract

Brain functional connectomes describe the coordination principles of neural systems. Understanding normative developmental connectomes is crucial for standardized growth assessment and early disease detection. However, functional connectome has been mostly studied using undirected functional connectivity estimated based on statistical correlation of functional MRI (fMRI) signals. Effective connectivity (EC), in comparison, builds on a generative model of neural interactions and provides directed connectivity strengths among neural populations. To understand how EC evolves with age, we charted the lifespan effective connectome of human brain networks based on high-quality fMRI data from the Lifespan Human Connectome Projects. We found that global and network EC follows an overall inverted U-shape development with an average maturation time at around 9 years of age, significantly earlier than functional connectivity. Regional EC strength exhibits diverse evolution patterns and is more variable during early development than later life, underscoring a critical early window of plasticity. Also, maturation of excitatory and inhibitory nodal EC follows opposite hierarchical sequences. Moreover, the development of nodal EC is constrained by the sensorimotor-association (S-A) gradient, primarily governed by inhibitory EC. Our work reveals fundamental development principles of directed causal interactions between functional networks, offering a foundation for more precise and individualized brain assessments.

The effective connectome of the human brain is charted from birth to 100 years of age, revealing a critical window of plasticity during early brain development and a sensorimotor-association gradient governed by inhibitory effective connectivity.