Lutein and Zeaxanthin Are Positively Associated with Visual-Spatial Functioning in Older Adults: An fMRI Study

Abstract

Lutein (L) and zeaxanthin (Z) are two xanthophyll carotenoids that have antioxidant and anti-inflammatory properties. Previous work has demonstrated their importance for eye health and preventing diseases such as age-related macular degeneration. An emerging literature base has also demonstrated the importance of L and Z in cognition, neural structure, and neural efficiency. The present study aimed to better understand the mechanisms by which L and Z relate to cognition, in particular, visual-spatial processing and decision-making in older adults. We hypothesized that markers of higher levels of L and Z would be associated with better neural efficiency during a visual-spatial processing task. L and Z were assessed via standard measurement of blood serum and retinal concentrations. Visual-spatial processing and decision-making were assessed via a judgment of line orientation task (JLO) completed during a functional magnetic resonance imaging (fMRI) scan. The results demonstrated that individuals with higher concentrations of L and Z showed a decreased blood-oxygen-level dependent (BOLD) signal during task performance (i.e., "neural efficiency") in key areas associated with visual-spatial perception, processing, decision-making, and motor coordination, including the lateral occipital cortex, occipital pole, superior and middle temporal gyri, superior parietal lobule, superior and middle frontal gyri, and pre- and post-central gyri. To our knowledge, this is the first investigation of the relationship of L and Z to visual-spatial processing at a neural level using in vivo methodology. Our findings suggest that L and Z may impact brain health and cognition in older adults by enhancing neurobiological efficiency in a variety of regions that support visual perception and decision-making.

Keywords: cognition; fMRI; older adults; visual-spatial reasoning; xanthophylls.

Figure 1

JLO task design. The figure provides a visual schematic of the judgement of line orientation (JLO) task. The two blocks (i.e., active baseline and JLO) were presented a total of six times, resulting in a total acquisition time of 6 min, 33 s. Ten stimuli were presented in each block in a random order with replacement for the active baseline and a sequential order from a library of 144 images for the JLO task.

Figure 2

Whole brain activation during JLO task. The figure depicts brain activation during the JLO task minus active baseline contrast (independent of lutein and zeaxanthin levels). Activation superimposed on a single-subject anatomical template in MNI space provided by MRIcron [56]. To conserve space, only five slices were selected to showcase task-related BOLD response based on the largest extent activation.

Figure 3

Relationship between lutein and zeaxanthin and brain activation. The figure depicts brain activation during the JLO task minus active baseline contrast that was significantly and negatively related to macular pigment optical density (MPOD) levels. In other words, individuals with lower levels of lutein and zeaxanthin showed an increased BOLD signal in these regions (i.e., “neural inefficiency). The activation is superimposed on a single-subject anatomical template in MNI space provided by MRIcron [56]. To conserve space, only five slices were selected to showcase task-related BOLD response based on the largest extent activation.

Figure 4

Relationship between lutein and zeaxanthin and brain activation. The figure depicts brain activation during the JLO task minus active baseline contrast that was significantly and negatively related to serum lutein and zeaxanthin levels. In other words, individuals with lower levels of lutein and zeaxanthin showed an increased BOLD signal in these regions (i.e., “neural inefficiency). The activation is superimposed on a single-subject anatomical template in MNI space provided by MRIcron [56]. To conserve space, only five slices were selected to showcase task-related BOLD response based on the largest extent activation.