The human brain is a remarkable organ, constantly processing information, adapting to new experiences, and shaping thoughts and actions. However, as people age, their brains undergo significant changes that influence how they think, learn, and remember. While cognitive decline is a widely recognised aspect of ageing, the precise ways in which structural changes alter brain function remain a subject of ongoing scientific investigation. A recent study from Monash University sheds light on this issue, revealing how ageing affects the brain’s ability to process information and maintain memory functions.
How ageing changes the brain
Over time, the adult brain experiences a natural decline in volume, particularly in key regions such as the cortex and hippocampus. These areas play a crucial role in memory and decision-making. Additionally, white matter, which facilitates communication between different brain regions, becomes less efficient. This deterioration could lead to slower cognitive processing and reduced adaptability when learning new tasks.
Using advanced imaging techniques, researchers have discovered that these structural changes also affect brain dynamics, specifically intrinsic neural timescales. These timescales determine how long different brain regions hold onto information before passing it along. Understanding these changes provides important insights into why memory and cognitive flexibility decline with age.
The brain’s internal rhythms
Each region of the brain operates at a distinct rhythm, known as its intrinsic neural timescale. Some regions process information rapidly, while others retain it for longer periods, allowing for deeper integration and complex thought. Higher-order brain areas, such as those involved in memory and reasoning, tend to have longer timescales compared to sensory regions, which require quick responses to external stimuli. Researchers have found that these intrinsic timescales are not fixed and change as people age. The latest study shows that older adults tend to have shorter intrinsic timescales, meaning their brains process information more quickly but struggle to retain it for extended periods. This shift has important implications for memory and cognitive function.
As people grow older, the brain’s adaptability, known as neuroplasticity, also declines. This makes it harder to form new connections and integrate fresh information. While younger brains are capable of reorganising pathways to compensate for damage or learning deficits, the ageing brain becomes less flexible in adapting to new experiences. This reduced plasticity could contribute to difficulties in adjusting to new environments or mastering unfamiliar skills later in life.
The impact of shorter intrinsic timescales
As the brain ages, it undergoes a natural pruning process, eliminating some neurons and synaptic connections. This reduction in connectivity raises questions about how efficiently the brain can process and retain information. By comparing the brains of younger and older adults, researchers found a clear link between ageing, shorter intrinsic timescales, and reduced grey matter volume.
The findings suggest that while ageing brains may become more reactive, they also lose the ability to sustain and integrate information over time. This could explain why older individuals sometimes struggle with complex cognitive tasks that require prolonged attention or deep processing. The study also identified a direct relationship between shorter intrinsic timescales and lower performance in memory-based tasks.
Memory and perception in an ageing brain
To explore how these changes affect cognition, researchers examined mnemonic discrimination ability, which refers to the brain’s capacity to distinguish between similar but distinct stimuli. In the study, participants completed a visual memory task that involved identifying previously seen images and differentiating them from slightly altered versions.
Older adults with shorter intrinsic timescales performed worse on this task, particularly in regions associated with visual processing, such as the cuneus. This suggests that reductions in intrinsic timescales may impair the brain’s ability to maintain stable mental representations. As a result, ageing individuals may find it harder to recognise subtle differences in objects or recall specific details from past experiences.
These findings align with common experiences among older adults, such as difficulty in remembering names, distinguishing between similar-looking faces, or recalling where an item was last placed. The study’s insights into neural processing speeds may help explain why such memory-related issues become more frequent with age.
Insights from computational modelling
To gain a deeper understanding of these changes, researchers developed a computational model simulating brain networks at different stages of ageing. By adjusting the density of neurons and synaptic connections, they replicated the structural decline seen in older adults.
The model revealed a key shift: In young adults, brain regions function near a “critical branching” state—an optimal balance where neurons are well-connected, allowing efficient information processing. However, in older adults, the loss of neurons and synapses shifted brain dynamics toward a more “subcritical” state, in which information fades too quickly. This not only aligned with the MRI findings but also provided a theoretical explanation for why intrinsic timescales shorten with age. As the brain loses connectivity, its ability to sustain activity over time diminishes, making it harder to retain and process information.
According to Dr Kaichao Wu, one of the study’s authors, these findings can be understood through the concept of critical slowing down, where the brain’s ability to sustain long-range interactions weakens over time. As the system moves further from an optimal “critical” state, cognitive function is increasingly affected.
By refining these models further, researchers hope to predict how different brain regions decline at varying rates and to explore whether interventions, such as cognitive training or pharmacological treatments, might help restore some of the lost functionality.
Can cognitive decline be slowed?
While ageing is inevitable, cognitive decline does not have to be. Understanding how the brain changes over time allows researchers to explore potential interventions to maintain mental function in older adults. The study highlights the intricate relationship between brain structure and function, offering valuable insights into why cognitive abilities diminish with age.
Future research may focus on ways to counteract these effects. Strategies such as cognitive training, physical exercise, diet and sleep quality have been linked to improved brain function in ageing individuals. Additionally, advancements in neuroscience may lead to new therapeutic approaches aimed at preserving neural connections and optimising brain dynamics.
As scientists continue to uncover the mechanisms behind brain ageing, the question remains: what steps can individuals take today to protect their cognitive health in the future? With growing knowledge in neuroscience, people may soon have more tools at their disposal to keep their minds sharp for longer.
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Journal reference
Wu, K., & Gollo, L. L. (2025). Mapping and modelling age-related changes in intrinsic neural timescales. Communications Biology, 8(1), 167. https://doi.org/10.1038/s42003-025-07517-x.
