It's odd how things unfold.

Yesterday, as I was reading an article by two Stony Brook psychiatrists in the Journal of Child and Adolescent Psychopharmacology, I came across a word I had not heard before. It seems that parents of children with mood disorders occasionally observe manic-like rages in their children that their teachers never see. In the psychiatrists' discussion of this phenomenon, they said that although the rages "clearly develop in the context of a mood disorder, the mood is probably not mania and is not ultradian cycling." Hmm…

A quick trip to Wikipedia gave me to know that 'ultradian' refers to biological "cycles repeated throughout a 24-hour circadian day." In other words, the episodes the parents observe are not symptoms of a rapid cycling bipolar disorder that crops up on the way home from school.

While I was at 'Ultradian', another phrase caught my eye: nostril dilation. There, amid a list of ultradian cycles that include urination, bowel activities and appetite, was something I have been wondering about all my life. Maybe you have been wondering about it too.

Quite often, as very late night dissolves into very early morning, I wake up with one nostril completely blocked and the other perfectly patent. Sometimes it's the right that's blocked and sometimes the left. It's an annoying experience that I wish would go away. I have always interpreted it in terms of hydrodynamics, thinking that one nostril was filled with (dare I say it) snot, while the other was somehow miraculously empty. I imagined that by turning one way or the other, I could coax the offending ooze to flow out of what I imagined to be a maze of contorted sinus cavities and let me go back to sleep. Wrong.

A click on the nostril dilation hyperlink brought me to The Nasal Cycle, "the alternating congestion and decongestion of the nostrils in humans." It has nothing to do with snot and everything to do with the autonomic nervous system and erectile tissue inside the nose.

I wish I had paid closer attention when the sympathetic and parasympathetic nervous systems were being discussed in class, because it turns out that they are the true culprits in the nasal congestion/decongestion saga. The nasal cycle occurs because a branch of the sympathetic nervous system dominates one side of the body and a branch of the parasympathetic nervous system dominates the other. After some period of time (don't ask, it's complicated) they switch. So far as I can make out, when the parasympathetic is in control, the arterioles in the nasal mucosa dilate, causing them to swell; when the sympathetic dominates, the vessels constrict and the nasal passages open.

David S. Shannahoff-Khalsa, BA

Completely outside my ken, a huge literature has developed around the nasal cycle partly because it is a readily available marker for other ultradian cycles and partly because of its connections with the ancient yogic practice of alternate nostril breathing. The Wiki page points to a review article by David S. Shannahoff-Khalsa, BA, from the Institute for Nonlinear Science at the University of California, San Diego, that has 106 footnotes. In 1927, an otolaryngologist named Dr. Dewey R. Heetderks from Grand Rapids Michigan published an article in the American Journal of the Medical Sciences titled Observations on the Reaction of Normal Nasal Mucous Membrane, in which he estimated that 80% of people experience the nasal cycle. More recently a pair of doctors from the UK conducted a small experiment and concluded that the number is probably closer to 20%. Apparently I am one of them.

That mystery solved, my brief encounter with the word 'ultradian' generated another. Why should 'ultradian' refer to cycles of less than a day and 'infradian' refer to cycles longer than a day (like the 28-day menstrual cycle)? If 'ultra' means more and 'infra' means less shouldn't ultradian cycles last more than a day and infradian cycles less? Unable to find an answer in the OED, I went across the hall to the chronobiology lab where Larry Morin, one of the world's leading experts on circadian rhythms, has his office. "That's just the way it is," he told me somewhat dismissively, although he confessed that earlier in his career he had come close to submitting an article with the terms reversed. We decided that 'ultra' and 'infra' refer to the frequencies of the cycles. If the cycles occur more frequently than every 24 hours, they are ultradian; if they occur less frequently, they are infradian.

It still doesn't sound right, but that's just the way it is.