Perceptual learning and changes in white matter in the aged brain revealed by diffusion-tensor imaging (DTI)

Abstract

An extensive body of research has shown that vision declines with increased age. Recent research (Yotsumoto et al., 2008; Ni et al., 2007) has shown that perceptual learning can be used to improve visual performance among older subjects (age 65 or older) and that the improved performance is associated with an increase in BOLD signal localized to a trained part of the visual field. An important question is whether the changes in BOLD signal are associated with anatomical changes. To address this question, we used diffusion tensor fractional anisotropy (FA) as a method to index white matter density changes in older subjects trained using perceptual learning. Nine older subjects aged 65-80 underwent three behavioral training sessions of a texture discrimination task (TDT) (Karni and Sagi, 1991). Each session lasted about 45 minutes and was conducted on three separate days. They also participated in two MRI /fMRI sessions before and after the three training sessions. In MRI/fMRI sessions, FA values were obtained using DTI, as well as BOLD activities during the task. Results indicated that FA values decreased below the regions of visual cortical areas retinotopically corresponding to the location of the trained stimulus (trained regions) when compared to those before the training. These findings were associated with improved TDT performance after training and significantly larger BOLD signal in the trained region than untrained regions. These results raise the possibility that at least with older people long-term performance and physiological changes are supported by anatomical changes.

Footnotes

 NIH-NEI R21 EY018925, NIH-NEI R01 EY015980-04A2, NIH-NEI R01EY019466, NIH-NIA R01 AG031941, JSPS.