Structural Basis of Cognitive Compensation in Healthy Brain Aging: Frontal and Occipital Gray Matter Correlates of Cognitive Functioning

Understanding healthy aging is becoming increasingly important as a larger number of us live longer. Aging involves structural and functional changes in the brain, with the frontal lobe among the first regions to deteriorate, and the occipital among the last (Lee & Kim, 2022). Despite the common misconception that old age is a period of declining mental abilities and rigidity, cognitive neuroscience shows that older adults flexibly use their neural and cognitive resources, recruiting new neural regions and cognitive processes when necessary (Shafto et al., 2014). Functional neuroimaging of cognitive aging has revealed a posterior-to-anterior shift in aging brain activity, known as PASA (i.e., Posterior-Anterior Shift in Aging), where the frontal lobe is shown to play a compensatory role in maintaining cognitive functioning. Age-related increases in frontal activity had a negative correlation with age-related occipital activity decline and a positive correlation with performance (Davis et al., 2008). This study explores the structural basis of this cognitive compensation, in the framework of PASA model. Using data from the Cambridge Centre for Ageing and Neuroscience (Cam-CAN) cohort (N=549, aged 18–87 years), we analyzed gray matter volume (GMV) in frontal and occipital lobes using structural MRI, alongside cognitive performance measured by the Cattell Culture Fair Test. The Posterior-Anterior (PA) ratio (occipital GMV/frontal GMV) was computed to assess relative changes in the GMV of the frontal and occipital lobes. Contrary to expectations, a weak positive correlation was shown between PA ratio and age (r=0.12, p=0.004), indicating a slightly higher occipital-to-frontal GMV ratio with age. Younger adults displayed significantly greater GMV in both lobes and superior cognitive performance compared to older adults (p<0.001). Higher education was associated with increased GMV and cognitive scores. These findings suggests that brain structure may not fully support compensatory mechanisms maintaining cognitive functioning in healthy aging, highlighting the need for further investigation into the structural correlates of cognitive compensation in aging.