A retinohypothalamic pathway in man: light mediation of circadian rhythms.
It has been proposed that, in animals, a retinohypothalamic pathway exists which mediates the synchronization of the diurnal light-dark cycle with the central neural components regulating endogenous rhythms. There have been numerous anatomic, physiologic and behavioral investigations to substantiate this proposed connection in experimental animals. Morphologic investigation of a retinohypothalamic tract in man has awaited the development of a technique capable of axonal tracing in the human brain. The paraphenylenediamine method was applied to 7 post-mortem human brains. Degenerated axons were found in the suprachiasmatic nuclei of the hypothalamus in each of the 4 patients who had incurred prior optic nerve damage. The retinosuprachiasmatic pathway may be the anatomical substrate for the integration of retinal light information with endogenous rhythms in man.
D000368:Aged; D001369:Axons / Q000648:ultrastructure; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D007031:Hypothalamus / Q000033:anatomy & histology*; D008027:Light; D008297:Male; D008875:Middle Aged; D009410:Nerve Degeneration; D009897:Optic Chiasm / Q000033:anatomy & histology; D009900:Optic Nerve / Q000033:anatomy & histology; D012160:Retina / Q000033:anatomy & histology*; D012165:Retinal Ganglion Cells / Q000648:ultrastructure; D013493:Suprachiasmatic Nucleus / Q000033:anatomy & histology; D014795:Visual Pathways / Q000033:anatomy & histology