Wordsworth wrote: “Our birth is but a sleep and a forgetting…”
Now researchers indicate that sleep itself is a forgetting:
In 2003, Giulio Tononi and Chiara Cirelli, biologists at the University of Wisconsin-Madison, proposed that synapses grew so exuberantly during the day that our brain circuits got “noisy.” When we sleep, the scientists argued, our brains pare back the connections to lift the signal over the noise.
In the years since, Dr. Tononi and Dr. Cirelli, along with other researchers, have found a great deal of indirect evidence to support the so-called synaptic homeostasis hypothesis…
Luisa de Vivo, an assistant scientist working in their lab, led a painstaking survey of tissue taken from mice, some awake and others asleep. She and her colleagues determined the size and shape of 6,920 synapses in total.
The synapses in the brains of sleeping mice, they found, were 18 percent smaller than in awake ones. “That there’s such a big change over all is surprising,” Dr. Tononi said.
The second study was led by Graham H. Diering, a postdoctoral researcher at Johns Hopkins University. Dr. Diering and his colleagues set out to explore the synaptic homeostasis hypothesis by studying the proteins in mouse brains. “I’m really coming at it from this nuts-and-bolts place,” Dr. Diering said.
In one experiment, Dr. Diering and his colleagues created a tiny window through which they could peer into mouse brains. Then he and his colleagues added a chemical that lit up a surface protein on brain synapses.
Looking through the window, they found that the number of surface proteins dropped during sleep. That decline is what you would expect if the synapses were shrinking.
(A window into mouse brains? Reminds me why I never became a medical researcher.)
Shakespeare described sleep well (he described most things well):
Methought I heard a voice cry ‘Sleep no more!
Macbeth does murder sleep’, the innocent sleep,
Sleep that knits up the ravell’d sleeve of care,
The death of each day’s life, sore labour’s bath,
Balm of hurt minds, great nature’s second course,
Chief nourisher in life’s feast,–
[NOTE: The title of this post isn’t just a restaurant in Big Sur with an astounding setting, it’s “a medicine for sorrow, literally an anti-depressant – a ‘drug of forgetfulness’ mentioned in ancient Greek literature and Greek mythology, depicted as originating in Egypt.”]