Quantifying Age-Associated Cortical Complexity of Left Dorsolateral Prefrontal Cortex with Multiscale Measurements.

BACKGROUND Cortical complexity plays a central role in the diagnosis and prognosis of age-related diseases. However, little is known about the regional cortical complexity in the context of brain atrophy. OBJECTIVE We aimed to systematically examine the age-related changes of the cortical complexity of left dorsolateral prefrontal cortex (DLPFC) and its subregions. METHODS Two hundred and fourteen cognitively normal adults drawn from the Open Access Series of Imaging Studies (OASIS) were divided into four age groups: young, middle-aged, young-old, and old-old. Based on structural magnetic resonance imaging (sMRI) scans, the multiscale measures of cortical complexity included cortical thickness (mm), surface area (mm2), grey matter volume (mm3), density, gyrification index (GI), and fractal dimension (FD). RESULTS Advancing age was associated with reduced grey matter volume, pial surface area, density, and FD of left DLPFC, but correlated with increased cortical thickness and GI. Volumetric measures, cerebrospinal fluid volume in particular, showed better performance to discriminate young-old adults from old-old adults, while FD was more sensitive than the volumetric measures to discriminate young adults and middle-aged adults than the other measures. CONCLUSION This is the first demonstration that chronological age has a pronounced and differential effect on the cortical complexity of left DLPFC. Our findings suggest that surface-based measures of cortical region, thickness, and gyrification in particular, could be considered as valuable imaging markers for the studies of aging brain and neurodegenerative diseases.