Age Effect on FMRI Using Grating Visual Stimuli

Abstract

Abstract: : Purpose: To assess the relationship between visual function based on BOLD-contrast fMRI and age. Methods: BOLD-contrast FMRI at 1.5T was performed while subjects viewed two sinusoidal gratings of 1 cpd or 2 cpd (counterphased at 4 Hz and at 50% contrast). Gratings were viewed binocularly. Normal subjects (n = 8, with an age range of 22–64 yr) were recruited for this study. FMRI analysis was constrained to the occipital cortex, posterior to the parieto-occipital sulcus. Within this region of interest, the total area (total number of activated voxels) and mean level (Z-score) of activation were assessed. Linear regression analysis was utilized to quantify the relationship between age and fMRI response across gratings. Results: There was a significant age effect on both area (P=0.01, R²=0.68) and level (P=0.01, R²=0.66) of BOLD response to the 1-cpd grating. The FMRI response decreased as age increased. There was no significant correlation between age and area (P=0.16, R²=0.30) or level (P=0.32, R²=0.16) of response to the 2-cpd grating. Conclusions: There is a significant relationship between age and BOLD-contrast FMRI response. The total area and mean level of activation decreased with age. Thus, age should be considered in FMRI studies involving the visual cortex, at least for gratings of 1 cpd.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, S • aging