Cortical thickness, measured on magnetic resonance images, correlates with cognitive performance because it indexes the underlying microstructure and the brain’s capacity for local information processing. Cortical thickness reflects dendritic arborization, synaptic density, glial support, and layers of neurons; changes in any of these elements alter signal integration and therefore cognitive abilities. This relationship is not strictly causal, but thickness serves as a reliable biomarker across many studies linking structure to functions such as memory, executive control, and processing speed.
Biological mechanisms
During development, increases in thickness often reflect synaptogenesis and growth of dendrites, while later adolescent thinning largely reflects synaptic pruning and increased myelination that refine networks for efficient processing. Tomas Paus at University of Toronto has described how adolescent cortical remodeling aligns with the emergence of higher-order cognitive skills. In aging, Anders M. Fjell and Kristine B. Walhovd at University of Oslo have documented widespread cortical thinning associated with declines in episodic memory and processing speed, linking structural loss to cognitive trajectories. Mechanistically, age-related thinning can arise from neuronal shrinkage, loss of synapses, reductions in dendritic complexity, and vascular or inflammatory changes—all of which diminish computational capacity in affected regions.
Environmental, cultural and clinical implications
Cortical thickness is shaped by lifelong experience and context. Long-term mental training and enriched environments are associated with regional increases or preserved thickness; Eileen Luders at University of California Los Angeles has reported thicker cortex in regions of long-term meditators. Physical activity and cardiovascular health also modulate structural aging; Kirk I. Erickson at University of Pittsburgh has shown relationships between exercise and preserved brain structure in older adults. Richard J. Haier at University of California Irvine has linked regional cortical measures to individual differences in intelligence, while Arthur W. Toga at University of Southern California has advanced methods that make these comparisons robust across populations.
Consequences of the cortical thickness–cognition link include potential use of thickness as a biomarker for early detection of risk, targets for intervention, and metrics for evaluating public-health strategies. However, interpretation must account for measurement variability, socioeconomic and territorial influences such as pollution or nutrition, and the fact that network-level connectivity often matters as much as localized thickness. Thickness indicates biological capacity but does not fully determine cognitive destiny.