 Both Robert Moore at the University of Chicago and Irving Zucker at the University of California, Berkeley linked the SCN to circadian rhythmicity at the same time by lesioning regions of the brain and observing their effects on circadian rhythms.When the SCN region was lesioned in rodents, the rodents did not exhibit circadian rhythms, which established the SCN as the circadian pacemaker.Robert Moore and David Klein first studied the SCN in the context of melatonin secretion by the pineal gland in 1974.