Abstract
Purpose:
Omega-3 fatty acids are essential for normal development and function of the retina and brain, where they are present at very high levels in the form of docosahexanoic acid (DHA). Monkey and human infants with low intake show delayed visual acuity development, and lack of these lipids has also been linked to changes in behavior and cognitive function. Using resting-state functional connectivity MRI (rs-fcMRI), we mapped large-scale functional brain organization in monkeys differing in life-long intake of omega-3 fatty acids. We hypothesized that low dietary levels would decrease functional connectivity within the visual system, and more generally throughout the brain.
Methods:
Fifteen rhesus monkeys were fed semisynthetic diets from birth until 17-19 year of age. The diets had different levels and sources of omega-3 fatty acids: 1) high DHA (N=4), 2) high alpha-linolenic acid (ALA), DHA’s dietary precursor (N=4), or 3) very low ALA (omega-3 deficient) (N=7). RS-fcMRI scans were acquired under 1% isoflurane anesthesia. Functional connectivity analyses assessed correlation maps for individual seed regions and patterns of correlated activity across the whole brain.
Results:
In the deficient group, connectivity of both the lateral geniculate nucleus and the superior colliculus with primary visual cortex (V1) was reduced relative to monkeys fed DHA. Correlation maps also showed prominent changes in cortico-cortical connectivity, including weaker positive and negative correlations throughout the brain. In monkeys fed DHA, modular brain organization was characterized by highly correlated distributed systems similar to those previously identified in humans, such as the default-mode network, frontoparietal network, and cingulo-opercular network, whereas deficient animals showed less coherence within the default system and unusually high integration of V1 with the ventral visual pathway.
Conclusions:
These findings add to the known effects of omega-3 fatty acid deficiency on the visual system and brain function. They may have arisen developmentally, over the lifespan, or in relation to aging. We found novel evidence that DHA consumption enhances functional cortical relationships and is associated with brain organization more closely resembling the healthy human brain. These results point to a role for DHA in maintaining key distributed systems involved in visual and higher-order processing.
Keywords: 755 visual cortex •
618 nutritional factors •
583 lipids