MIT neuroscientists have discovered that the adult brain contains millions of “silent synapses” — immature connections between neurons that remain inactive until they’re recruited to help form new memories. It was believed that silent synapses were present only during early development, when they help the brain learn the new information. However, the new MIT study revealed that in adult mice, about 30 percent of all synapses in the brain’s cortex are silent.

When we press our temples to soothe an aching head or rub an elbow after an unexpected blow, it often brings some relief. It is believed that pain-responsive cells in the brain quiet down when these neurons also receive touch inputs, say scientists at MIT’s McGovern Institute for Brain Research, who for the first time have watched this phenomenon play out in the brains of mice.

Many Covid-19 patients who have been treated for weeks or months with mechanical ventilation have been slow to regain consciousness even after being taken off sedation. A new article in PNAS offers the hypothesis that this peculiar response could be the effect of a hibernation-like state invoked by the brain to protect cells from injury when oxygen is scarce.