Age-related degeneration of the fornix in the human brain: a diffusion tensor imaging study.

As a part of the Papez circuit, the fornix carries information on episodic memory. Several diffusion tensor imaging (DTI) studies have reported on changes in the fornix that occur with aging; however, these studies have been controversial. Using DTI, we attempted to investigate age-related changes of the fornix in the human brain. Sixty subjects (30 males, 30 females; mean age, 49.2 years; range, 20-78 years) were recruited. We categorized subjects into three groups, including young (20-39 years), middle-aged (40-59 years), and older (60-79 years) adults. DTIs were acquired using a sensitivity-encoding head coil on a 1.5 T. We divided the whole fornix into three parts (column, body, and crus) and constructed tractography for each part. We measured fractional anisotropy (FA), apparent diffusion coefficient (ADC), and tract number for each part of the fornix. In all three parts of the fornix, the FA value and tract number decreased, whereas ADC value increased with aging. In addition, a linear regression model was fitted to all three DTI parameters in each part of the fornix. Degenerative change of the fornix in the human brain appears to have occurred at a near constant rate from the 20s to the30s throughout the lifespan.