When we are in a deep slumber our brain's activity ebbs and flows in big, obvious waves, like watching a tide of human bodies rise up and sit down around a sports stadium. It's hard to miss.
Now, Stanford researchers have found, those same cycles exist in wake as in sleep, but with only small sections sitting and standing in unison rather than the entire stadium. It's as if tiny portions of the brain are independently falling asleep and waking back up all the time.
What's more, it appears that when the neurons have cycled into the more active, or "on," state they are better at responding to the world. The neurons also spend more time in the on state when paying attention to a task. This finding suggests processes that regulate brain activity in sleep might also play a role in attention.
"Selective attention is similar to making small parts of your brain a little bit more awake," said Tatiana Engel, a postdoctoral fellow and co-lead author on the research, which is scheduled to publish Dec. 1 in Science. Former graduate student Nicholas Steinmetz was the other co-lead author, who carried out the neurophysiology experiments in the lab of Tirin Moore, a professor of neurobiology and one of the senior authors.
How Water Conducts Electricity
Scientists have taken spectroscopic snapshots of nature's most mysterious relay race: the passage of extra protons from one water molecule to another during conductivity.
The finding represents a major benchmark in our knowledge of how water conducts a positive electrical charge, which is a fundamental mechanism found in biology and chemistry. The researchers, led by Yale chemistry professor Mark Johnson, report their discovery in the Dec. 1 edition of the journal Science.
For more than 200 years, scientists have speculated about the specific forces at work when electricity passes through water – a process known as the Grotthuss mechanism. It occurs in vision, for example, when light hits the eye's retina. It also turns up in the way fuel cells operate.
But the details have remained murky. In particular, scientists have sought an experimental way to follow the structural changes in the web of interconnected water molecules when an extra proton is transferred from one oxygen atom to another.
"The oxygen atoms don't need to move much at all," Johnson said. "It is kind of like Newton's cradle, the child's toy with a line of steel balls, each one suspended by a string. If you lift one ball so that it strikes the line, only the end ball moves away, leaving the others unperturbed."
Johnson's lab has spent years exploring the chemistry of water at the molecular level. Often, this is done with specially designed instruments built at Yale. Among the lab's many discoveries are innovative uses of electrospray ionisation, which was developed by the late Yale Nobel laureate John Fenn.