Regional frontal cortical volumes decrease differentially in aging: an MRI study to compare volumetric approaches and voxel-based morphometry.

Recent neuroimaging studies suggest that the frontal lobes are the part of the brain most profoundly affected by the aging process. The present study investigated whether subregions within the frontal cortex show different patterns of brain aging. Magnetic resonance images of 57 healthy participants between 21 and 81 years old were used to measure regional frontal gray matter volumes in three ways: a manual tracing method, a semiautomatic "Talairach boxes" volumetric method, and voxel-based morphometry. Seven regions within each hemisphere were manually traced: precentral gyrus, inferior frontal gyrus, dorsolateral frontal cortex, ventral medial region, lateral orbital region, anterior cingulate, and frontal pole. With the semiautomatic approach, four regions were measured: lateral, orbital, and medial frontal regions and frontal pole. Advancing age was strongly associated with decreases in the volume of the whole frontal cortex. Differential age effects on the volumes of frontal subregions were dependent on the method applied. According to the manual approach, age-related volume decreases were strongest in the lateral and orbital frontal gray matter. The semiautomatic and voxel-based analyses found that age effects were most prominent within the lateral frontal and cingulate regions. Overall, it was concluded that although semiautomated and voxel-based methods can provide a reasonable estimate of regional brain volume, they cannot serve as a substitute for manual volumetry.