Mydriasis pupil) or overactivity of the sympathetic nervous system (SNS). Pupil diameter also increases in reaction to cognitive tasks requiring memory and attention, and this phenomenon is used as an indicator of mental activation (‘arousal’) in psychophysiological experiments . Natural release of the hormone oxytocin can cause mild to moderate mydriasis. Parasympathetic fibers travel with cranial nerve III, the oculomotor nerve, to innervate the circular layer of muscle of the eye (sphincter pupillae). Damage to this nerve typically manifests itself as mydriasis, because the sympathetic supply to the pupil, which causes mydriasis, remains unaffected, and therefore unopposed. Multiple central nervous system
Sum of normally distributed random variables variables is normal, with its mean being the sum of the two means, and its variance being the sum of the two variances (i.e., the square of the standard deviation is the sum of the squares of the standard deviations). If one is to get the conclusion that the sum is normally distributed, the assumption that "X" and "Y" are independent cannot be dropped, although it can be weakened to the assumption that "X" and "Y" are jointly, rather than separately, normally distributed. (See here for an example.) The result about the mean holds in all cases, while the result