Relationships between cognitive function and frontal grey matter volumes and thickness in middle aged and early old-aged adults: the PATH Through Life Study.

The study examined the relationship of lateral frontal cortical volume and thickness with cognitive function in two samples of healthy middle aged (MA, 44-48 years old) and early old-age (OA, 64-68 years old) adults. T1-weighted magnetic resonance imaging scans were acquired in 400 MA and 397 OA adults from respective random community samples. Cortical volumes and thickness were measured with a surface-based segmentation procedure (http://surfer.nmr.mgh.harvard.edu). Volumes of lateral frontal grey matter were found to be significantly lower for OA than MA. Structure-function relationships were investigated using path analyses. In OA, smaller lateral frontal volumes were associated with better episodic memory (EM) (p<0.012, B=-0.117), and Symbol-Digit Modalities Test (SDM) (p<0.031, B=-0.118) performance. Smaller frontal cortical thickness was also associated with better EM (p<0.01) and SDM (p<0.01) performance in OA. However, in MA greater cortical thickness was associated with better EM and (p<0.01) and reaction time (RT) (p<0.01). OA cohort showed significant positive correlations between Total Brain Volume and SDM, Digit-Backwards span and RT. Possible explanations and implications of the relationships in the context of cognitive aging in healthy adults, and limitations of cross-sectional research are discussed.