2021 Volume 58 Issue 2 Pages 175-181
In the daily living, we use visual non-image-forming and image-forming pathways to adjust the central clock and monitor the surrounding conditions. In the former, melanopsin-containing retinal ganglion cells react to light, and the signal is projected into the suprachiasmatic nucleus or the pretectal olivary nucleus, inducing the central clock adjustment or the pupillary reaction. Visual information signaled by cones and rod cells is propagated to the occipital lobe and then sent to the dorsal and ventral pathways. These are called bottom-up circuits. Visual information through the ventral pathway is modified by the top-down circuit of the upper center while being matched with visual memory to form an inner image in the brain. The inner image is then determined whether correct or not by the reality-monitoring function of the upper center. In Parkinson’s disease, both image and non-image forming pathways are impaired, and sleep disorders are caused by the modulation of the central clock, and visual hallucinations are elicited by the failure of visual information processing..
