on February 8th, 2016 No Comments
(Sigh…) How should I know? Don’t I already have enough on my mind?
As we all well know, sighing is a long, deep involuntary inhalation accompanying sensations of yearning, sadness, relief, boredom, exhaustion, or (see above) exasperation. Fewer of us know (at least I didn’t, but now I do!) that the typical person also sighs spontaneously about every five minutes or so.
If you’re a mouse, you do it much more often – as much as 40 times per hour. (Nobody said it would be easy, little mousie.)
Those spontaneously sighs (and all the other ones), it’s thought, may be helping to keep our half-billion or so alveoli – the tiny sacs through which our lungs exchange oxygen and carbon dioxide with the atmosphere that surrounds us – pumped up and operating efficiently.
In a series of experiments described in a Nature study, Krasnow’s team, along with colleagues at Stanford and UCLA, painstakingly employed genetic, pharmacological and surgical techniques to map out a precise set of nerve circuits in the brain that are essential to the act of sighing. They showed that a sigh results when inhalation-initiating nerve impulses generated rhythmically within these circuits double up: One impulse effectively laps another and rides piggyback on top of it, producing a deeper, drawn-out inhalation.
The experiments were performed in mice. But the brain circuits involved are sufficiently ancient that our common ancestors no doubt had them, too – and therefore we (probably) do, too, or at least very similar ones.