A role for the macular carotenoids in visual motor response

Objectives: Lutein (L), zeaxanthin (Z), and meso-zeaxanthin are the dominant carotenoids within the central retina (there, termed macular pigment, MP). L is also the dominant carotenoid in the brain. The presence of L and Z in both motor and visual areas of the central nervous system is consistent with a role of these carotenoids in visual-motor behavior. The purpose of this study was to provide a first test of this hypothesis. Methods: Balance ability (measured via the Standing Leg Test) and simple reaction time (measured via a stimulus appearing in one of four quadrants of a computer monitor) were measured in 49 subjects (mean age = 54.8 years). Fixed and variable reaction time, and coincidence anticipation ability (estimating the arrival of the stimulus at a target location moving at four velocities) were assessed in 106 younger subjects (mean age = 23 years) using a customized device. MP optical density was measured in all subjects via customized heterochromatic flicker photometry. Results: MP optical density was significantly (P < 0.05) related to reaction time and to balance ability for the older subjects. Even for the younger group, MP optical density was significantly (P < 0.05) related to fixed and variable position reaction time, as well as coincidence anticipation errors, at high speed. Discussion: L and Z status has been linked to benefits in cognitive function in past research. The present results, and the selective presence of L and Z in visual and motor areas in the brain, are consistent with these carotenoids having a role in visual and motor integration.