What is real and what is imagined? To try and answer that question, scientists monitored the brains of ferrets as the animals were forced to watch clips of "The Matrix."
The connection may not be so obvious, but the researchers worked from the assumption that ferret brains resemble human brains -- at least at a basic level. Scientists generally agree that you can see the rudiments of humans in mammals like ferrets. Then the team got inside the ferrets' heads.
The researchers at the University of Rochester in New York wired the brains of ferrets as the animals watched the mind-bending 1999 movie, as well as when they watched TV static and when they sat in complete darkness. The lead researcher, Michael Weliky, says the study demonstrated a lesson that Keanu Reeves' character, Neo, learned in the first Matrix movie -- that reality is more than what meets the eye.
"When we look at an object, 80 percent of what we see is internally driven while only 20 percent has to do with the real thing," said Weliky, who is an assistant professor of brain and cognitive science. "The big question is, what is going on internally to create that picture?"
For the study, which appeared in a recent issue of the journal "Nature," Weliky and his colleagues implanted extremely fine electrodes into the visual cortex of ferrets. Some of the subjects were young and had just opened their eyes, others were slightly more mature animals and a third group was made up of adults. He then compared the brain activity among the three groups in darkness and as they watched the movie and the TV static.
He found that while the young ferrets showed almost no brain patterns that correlated with the different visual inputs, the adult ferrets' brains were teeming with orderly activity -- even as they sat in the dark.
When the adult animals saw the movie or the TV static, their brain activity increased by 20 percent and reflected the images they saw. Inside the minds of the young ferrets, meanwhile, there was activity, but it did not change or reflect according to whether it was in darkness, watching static or the sci-fi film classic.
Weliky says this suggests that as we grow and mature, our brains learn to identify outside images by matching them with our internal understanding of the world. While a young ferret (or child) may notice static or movies, it can't distinguish between them. Adults, meanwhile, have a history of vision to be able to distinguish between the two.
What was surprising is it appears that internal workings of the brain make up 80 percent of how the adult ferrets interpreted the external world. If extended to people, Weliky says this means our understanding of the world around us must be extremely limited to our own capacity to interpret reality.
"It's like the ocean -- where you have two-mile deep waters and tiny ripples at the surface," he said. "The ripples are the sensory input, underneath is the two-mile unknown internal activity."
There's an old joke that people only use about 10 percent of their brains and some have used this point to argue that the other 90 percent of the brain could be capable of detecting paranormal activity or could host another kind of enormous, untapped potential. But most cognitive scientists have dismissed the notion as impossible.
"Losing far less than 90 percent of the brain to accident or disease has catastrophic consequences," Barry Beyerstein of the Brain Behavior Laboratory at Simon Fraser University in Vancouver, British Columbia, wrote recently in "Scientific American."
What could be true, Beyerstein adds, is that a large part of the human brain operates without our awareness. He points to the ferret study as evidence.
"This and other research suggests that we may not always be as in charge as we might think," he said.
So what makes up that 80 percent to 90 percent of brain activity that seems to hum along on its own accord? To investigate that question, Weliky plans to return to his ferrets. The animals offer an advantage, he explains, because they open their eyes 30 days after being born. This means Weliky can calibrate his subjects more precisely according to their visual development.
Next, Weliky and his team plan to deprive a group of young and adult ferrets of outside stimulation. For all but six hours each day, they will reside in darkness and during those six hours, they will see only TV static.
"If we can see what happens in their brains when they haven't experienced a normal environment, then maybe we can answer what allows a normal organism to develop perception and interpretation," he said.
It may not sound pleasant for the ferrets, but Weliky jokes the animals already had a say in which of the "Matrix" trilogy films they would tolerate in the previous study.
"We tried showing them segments from the two second movies," he said, "but the ferrets refused to watch."