As we slip into deep sleep, higher regions of our brains take a vacation from each other, disconnecting so much that consciousness is snuffed out and a once highly integrated organ becomes separated, according to a groundbreaking experiment by University of Wisconsin-Madison researchers.
I've had the hemispheres of my brain wake up separately. Lemme tell ya... It can be quite disconcerting to see reality with one eye and a dream version of it with the other.
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There are a few popular theories on why that is. When you sleep, the parts of your brain that govern perception never shut down, but the parts that process input and allow us to define "reality" and our position in our world DO shut down. Dreams are, for the most part, just our imaginations running wild without the more civilized parts of the brain keeping it in check. The perceptive parts of our brain, seeking input, latch onto these imaginative wanderings and make them seem real.
At the same time this is going on, the brain is also "recharging" itself by allowing its neural receptors to rest. As the brain rests, it appears to randomly "test" itself by firing off signals to various neurons for reasons we don't quite understand. It's quite likely that the "faces from the past" phenomena happens when one of these random firings hits a neuron holding a long forgotten memory, and more complex dreams happen when the imaginative parts and perceptive parts of the brain try to make sense of these signals.
For example, one random neuron firing may remind you of a conversation you once had with a friend. Another random neuron firing may remind you of your grandmothers living room. Another random neuron firing might bring back the long forgotten face of a girl you once knew. Trying to make sense of these signals, the imaginative part of your brain combines them into a scene where you're sitting in your grandmothers living room talking to a girl you haven't seen in decades as if she were an old friend. Since the parts of your brain that separate reality from fiction are sleeping, the imagination takes that premise and runs with it, building a complete dream.
Yep, that's how I read it. Heck, might as well post the whole thing now.
Madison - As we slip into deep sleep, higher regions of our brains take a vacation from each other, disconnecting so much that consciousness is snuffed out and a once highly integrated organ becomes separated, according to a groundbreaking experiment by University of Wisconsin-Madison researchers.
The study, published today in the journal Science, not only helps explain the bedeviling concept of consciousness, but its approach also could be used to better understand, diagnose and treat diseases ranging from Alzheimer's to schizophrenia, according to scientists not associated with the research.
Beyond that, the study represents a major scientific advance in a field that long had been the province of philosophy.
"Understanding consciousness is no small thing," said Olaf Sporns, an associate professor of psychology at Indiana University. "It has become a scientific frontier. It's there from the moment we open our eyes in the morning."
It only has been in the last decade that neuroscientists have had the tools to study consciousness.
Using several of those innovations, including a sophisticated apparatus that can stimulate specific parts of the brain and monitor the ripple of brain waves that follow, the UW researchers designed and tested an approach that is a breakthrough in the field, said Sporns, who was not part of the study.
UW scientists, led by psychiatry professor Giulio Tononi, and researchers at the University of Milan in Italy, monitored brain activity in a small group of volunteers, both when they were awake and when they were in deep, dreamless sleep.
Dreamless sleep is the early period of rest also known as non-rapid eye movement sleep. Non-REM sleep was picked because when people wake from it they report little or no conscious awareness.
First, the researchers fitted the volunteers with an electroencephalography, or EEG, device, essentially a skullcap wired with 60 electrodes that pick up electrical activity throughout the brain.
Then they used a paddle-like device that generates a targeted magnetic pulse that travels through the skull into a specific brain region.
The idea was to use both devices to see if there was a difference in the way the brain responded when it was stimulated in both a conscious and unconscious state.
And there was.
During wakefulness, the magnetic pulses caused electrical activity that spread from roughly the midbrain out to the front, side and back of the brain.
But during deep sleep, the electrical activity essentially was confined to the immediate area of the magnetic pulse.
"Somehow it doesn't travel anywhere," said Tononi, senior author of the paper.
Tononi likened it to a bunch of trucks being dropped at a specific location in Milwaukee.
During wakefulness, the trucks move out along freeways and roads to places such as Madison and Chicago.
But during deep sleep, they stay in the area where they were dropped.
"It's as if the highways are there but they have been blocked by police," he said.
Tononi said the findings support the idea that consciousness is a state that depends on connectivity and the brain's ability to integrate information in groups of neurons around the brain.
Beyond that, consciousness is everything that a person experiences, he said.
"Think of it as what abandons us every night when we fall into dreamless sleep and returns the next morning," he wrote last year in a paper outlining his novel theory. "Without consciousness, as far as we are concerned, there would be neither an external world nor our own selves. There would be nothing at all."
Tononi said the next step is to use his technique on people during REM sleep - since dreaming is a form of consciousness - to see if connectivity returns during long, vivid dreams.
He also now is using the approach on people with schizophrenia, which is a form of altered consciousness.
Ultimately, he said, it might help target therapies for schizophrenics. In addition, the approach could be used for studying people with Alzheimer's and other dementias.
"This could be another tool to tell if brain regions are able to talk to each other," he said.
Still another application would be to use the technique on people who are in comas or vegetative states.
Sporns, of Indiana University, said the data in the study are very strong.
"There was a clear difference," he said. "(And) It's happening in the same brains. This is an excellent demonstration and a major breakthrough."
Over the last several years, a number of researchers have proposed various theories of consciousness. Tononi's theory now is emerging as the most viable, he said.
The study explains how the fading of consciousness during non-dreaming sleep is due to a breakdown of connectivity in the cortex, said Mircea Steriade, a professor of neuroscience at Laval University in Quebec City, Quebec.
"It advances our understanding," Steriade said. "Non-scientists should care about this research because it relates to what makes us humans."
