Developmental and aging changes in brain network switching dynamics revealed by EEG phase synchronization

Summary & key facts

Researchers recorded EEG from 111 healthy people aged 9 to 75 while they rested and while they listened to a simple sound task. They measured how much brain signals swung, how complex those swings were, and how brain regions briefly synced up with each other. They found two clear age patterns. First, slow brain rhythms and large-scale signal fluctuations steadily got weaker with age. Second, the way brain regions switched their brief synchrony followed an upside-down U shape: young adults showed the slowest but most varied and flexible switching, while children and older adults switched faster and in more predictable ways. A simple computer model of connected brain regions reproduced these patterns only when the simulated connections were at an intermediate, balanced level, suggesting young adults sit in a “sweet spot” for flexible brain coordination. The findings show measurable changes in how brains balance stability and flexibility across life, while noting that EEG has limited spatial detail and the model is a simplification.

Key facts:

• The study used EEG recordings from 111 healthy people between 9 and 75 years old during rest and a simple listening task to study brain variability over the lifespan.
• Measures of slow brain rhythms (low-frequency power), the size of signal swings, and signal complexity declined steadily as people got older, indicating weaker slow fluctuations and less large-scale coherence with age.
• The timing of brief synchrony between brain regions did not change linearly with age. Instead it followed an inverted U shape: young adults showed the most diverse and slowest switching patterns, while children and older adults had faster and more stereotyped switching.
• The researchers looked at rhythms from about 2–20 hertz. In the slow band (about 2–6 Hz), young adults had low average jump size but high variability across time. In the faster band (about 8–20 Hz), the pattern was reversed.
• To test why this happens, the team ran a computer model that mimicked ten simplified brain regions wired like the human brain. Only when connections in the model were at an intermediate, balanced strength did the simulated data match the flexible switching seen in young adults.
• The authors caution that EEG recordings blur where activity comes from on the scalp, and that the computer model is a simplified representation. These results describe patterns and suggest a mechanism, but they do not prove a single cause for the age differences.

Abstract

Author summary Brain activations fluctuate and synchronize according to functionally relevant patterns, both at rest and during task performance. Here, we investigated how these fluctuations change from childhood to older adulthood and what these changes reveal about healthy development and aging. Using electrophysiological brain activity recordings from 111 participants aged 9–75 years during rest and a cognitive task, we discovered two key developmental trajectories. First, a linear trend reflecting mainly a gradual weakening of slower brain rhythms with age. Second, an inverted U-shaped trend suggesting that neural flexibility peaks in young adults, who switch between neural synchronization states in uniquely diverse yet controlled ways, whereas children and older adults showed more rigid and predictable patterns. To explain this, we developed a computational model. The simulated data confirmed that young adults operate in a “sweet spot” of connectivity—balanced enough to support dynamic coordination without becoming unstable or overly rigid—unlike in childhood and older age, when connectivity becomes either too weak or too strong. Our work shows that age fundamentally reshapes how flexibly brain regions communicate. This provides sensitive markers for tracking brain health across the lifespan.