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 more general case we find that the closest point on the line to the origin is located a (signed) distance away, so that The same argument in higher dimensions shows that if then Now we are essentially done, because So in general, if then In the event that the variables "X" and "Y" are jointly normally distributed random variables, then "X" + "Y" is still normally distributed (see Multivariate normal distribution) and the mean is the sum of the means. However, the variances are not additive due to the correlation. Indeed, where ρ is the correlation. In particular, whenever ρ