Brain's 'radio stations' have much to tell scientists

Feb 07, 2011 By Michael C. Purdy
Neuroscientists have closely analyzed where and when the brain becomes active for many years, but now researchers at Washington University School of Medicine in St. Louis are gathering evidence that the frequency of that activity can be a source of important insights. The discoveries are made possible by a grid of electrodes temporarily installed directly on the surface of a patient's brain to help pinpoint the source of medication-resistant seizures. (ERIC C. LEUTHARDT, MD)

(PhysOrg.com) -- Like listeners adjusting a high-tech radio, scientists at Washington University School of Medicine in St. Louis have tuned in to precise frequencies of brain activity to unleash new insights into how the brain works.

“Analysis of brain function normally focuses on where brain activity happens and when,” says Eric C. Leuthardt, MD. “What we’ve found is that the wavelength of the activity provides a third major branch of understanding brain physiology.”

Researchers used electrocorticography, a technique for monitoring the brain with a grid of electrodes temporarily implanted directly on the brain’s surface. Clinically, Leuthardt and other neurosurgeons use this approach to identify the source of persistent, medication-resistant seizures in patients and to map those regions for surgical removal. With the patient’s permission, scientists can also use the electrode grid to experimentally monitor a much larger spectrum of brain activity than they can via conventional brainwave monitoring.

Scientists normally measure brainwaves with a process called electroencephalography (EEG), which places electrodes on the scalp. Brainwaves are produced by many neurons firing at the same time; how often that firing occurs determines the activity’s frequency or wavelength, which is measured in hertz, or cycles per second. Neurologists have used EEG to monitor consciousness in patients with traumatic injuries, and in studies of epilepsy and sleep.

In contrast to EEG, electrocorticography records brainwave data directly from the brain's surface.

“We get better signals and can much more precisely determine where those signals come from, down to about one centimeter,” Leuthardt, assistant professor of neurosurgery, of neurobiology and of biomedical engineering, says. “Also, EEG can only monitor frequencies up to 40 hertz, but with electrocorticography we can monitor activity up to 500 hertz. That really gives us a unique opportunity to study the complete physiology of brain activity.”

Leuthardt and his colleagues have used the grids to watch consciousness fade under surgical anesthesia and return when the anesthesia wears off. They found each frequency gave different information on how different circuits changed with the loss of consciousness, according to Leuthardt.

“Certain networks of brain activity at very slow frequencies did not change at all regardless of how deep under anesthesia the patient was,” Leuthardt says. “Certain relationships between high and low frequencies of brain activity also did not change, and we speculate that may be related to some of the memory circuits.”

Their results also showed a series of changes that occurred in a specific order during loss of consciousness and then repeated in reverse order as consciousness returned. Activity in a frequency region known as the gamma band, which is thought to be a manifestation of neurons sending messages to other nearby neurons, dropped and returned as patients lost and regained consciousness.

The results appeared in December in the Proceedings of the National Academy of Sciences.

In another paper that will publish Feb. 9 in The Journal of Neuroscience, Leuthardt and his colleagues have shown that the wavelength of brain signals in a particular region can be used to determine what function that region is performing at that time. They analyzed brain activity by focusing on data from a single electrode positioned over a number of different regions involved in speech. Researchers could use higher-frequency bands of activity in this brain area to tell whether patients:

• had heard a word or seen a word
• were preparing to say a word they had heard or a word they had seen
• were saying a word they had heard or a word they had seen.

“We’ve historically lumped the frequencies of brain activity that we used in this study into one phenomenon, but our findings show that there is true diversity and non-uniformity to these frequencies,” he says. “We can obtain a much more powerful ability to decode and cognitive intention by using electrocorticography to analyze these frequencies.”

Explore further: Memory relies on astrocytes, the brain's lesser known cells

More information:
-- Breshears JD, Roland JL, Sharma M, Gaona CM, Freudenburg ZV, Tempelhoff R, Avidan MS, Leuthardt EC. Stable and dynamic cortical electrophysiology of induction and emergence with propofol anesthesia. Proceedings of the National Academy of Sciences, Dec. 7, 2010.

-- Gaona CM, Sharma M, Freudenburg ZV, Breshears JD, Bundy DT, Roland J, Barbour D, Schalk G, Leuthardt EC. Nonuniofrm high-gamma (60-500 hz) power changes dissociate cognitive task and anatomy in human cortex. The Journal of Neuroscience, Feb. 9, 2011.

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Vaughn
not rated yet Feb 07, 2011
Biology is a manifestation of the laws of physics. It would follow that millions of years of evolution would result in the layering of modes of function to, in effect, do more with less adhering to one of the primary laws - conservation of energy. The utilization of frequency enables all of the wave-based communications strategies we are just beginning to explore in our nascent telecommunications industry.

Pretty sure biology uses frequency as it would all the other physics phenomenon considering biology is made of the physical world, one quark at a time...
kevinrtrs
1 / 5 (9) Feb 08, 2011
t would follow that millions of years of evolution would result in the layering of modes of function to, i


Do you really seriously believe that TIME will do all of this by itself? It's a nice cover-up for dodging that very important question of "HOW did it happen?". Leave anything to itself, including biological systems and they also follow the laws of physics - downward in energy levels, NOT upwards which is what evolutionary thought proposes.

So in that sense you are correct - the biological processes do adhere to the laws of physics. It's just not in the way you envisage since that is physically impossible.

It's physically impossible because of the number of reactions that would need to occur randomly to form something as organized as the brain. Every reaction requires energy, and there's just not enough energy in the whole universe for all those random "tries" to occur to produce a brain.

We were created. Period.
Eikka
5 / 5 (5) Feb 08, 2011
Leave anything to itself, including biological systems and they also follow the laws of physics - downward in energy levels, NOT upwards which is what evolutionary thought proposes.


You would have a point if there wasn't that big yellow ball up in the sky radiating more energy onto this planet every day. Adding energy adds complexity.
Eikka
5 / 5 (4) Feb 08, 2011
[there's just not enough energy in the whole universe for all those random "tries" to occur to produce a brain.


A brain is nothing more than a combination of more fundamental building blocks called cells, which in themselves are a combination of more fundamental units of proteins and lipids and amino acids.

Complexity builds on complexity. Once you have a brick, it takes little energy to build a brick wall even if you try the pieces together randomly, because the number of pieces is greatly reduced and so are the number of possible combinations.

And of course, any wall that doesn't work will fall down before you get to complete it, so it's eliminated automatically and no more energy is spent on it.

Once you have a brick wall, it takes little energy to build a brick house, even if you arrange the walls randomly. Again for the same reasons.

From a cell is a small step to a neuron, from which is a small step to a brain, from which is a small step to a bigger brain.
Eikka
5 / 5 (3) Feb 08, 2011
the number of reactions that would need to occur randomly to form something as organized as the brain


Is indeed very small, considering that brains and many other body parts are built as fractals. The physical structure itself can be constructed by relatively simple rules, once you have the building blocks available.

An architect who draws a house doesn't decide the position of every single brick to be laid. He simply draws a wall and says "bricks go here", and the already established method of building a brick wall is applied.
NotAsleep
1 / 5 (2) Feb 08, 2011
What is the purpose of this article? Apart from the second paragraph it makes no mention of how the experiment helped the seizure patient. On top of that, they can't do this to a healthy human brain so there's no true control group to draw correlations on how the brain is "supposed" to function
Godless_Heathen
3 / 5 (2) Feb 08, 2011
@Eikka - Thank you for saying so eloquently what I was thinking! Well done! People that suppose we were created don't seem to understand that all of this didn't happen by giant leaps, i.e. from monkey to man. Instead it happened in tiny, almost imperceptible steps.
trekgeek1
3.7 / 5 (3) Feb 08, 2011
@Eikka - Thank you for saying so eloquently what I was thinking! Well done! People that suppose we were created don't seem to understand that all of this didn't happen by giant leaps, i.e. from monkey to man. Instead it happened in tiny, almost imperceptible steps.


No, they do understand. They understand it didn't happen over night. They understand that the 2nd law of thermodynamics doesn't prohibit evolution. They understand it all. The problem is they intentionally lie to spread their beliefs. They lie to their children, and they lie to themselves in the hope that they will really start to believe in their holy book. They know their beliefs aren't supported by evidence and they doubt them. They hope that by repeating creationist propaganda, their doubt will fade, and they will actually start to believe before they die. They fear their hell that much.
T2Nav
5 / 5 (2) Feb 08, 2011
I think the most important word in Kevin's input is "Period". It means there will be no more discussion, no more thinking, no evaluation of the evidence in this matter.

The biggest difference between the hard-core religious and the scientific mindset is the ability to see new evidence and be willing to change how one believes the universe works. An astronomer sees that his planet-observations only make sense if the Sun, and not the Earth, is the center of the universe. A physicist smashes what are believed to be the basic bits of matter together, finding even smaller pieces, and welcomes the chance to go back to the drawing board. Astronomers see a cloud of green gas, or a nova-like flash that brightens and dims in a weird way and they don't ignore it-- they are excited about a chance to refine or correct their thoughts on how the universe works. Religion means if it's not in my book I'll just ignore it.
ekim
5 / 5 (1) Feb 09, 2011
Actually Kevin makes a strong case for abortion. Think about it, it is physically impossible for something as organized as the brain to form from a single cell. It's physically impossible because of the number of reactions that would need to occur for a single cell to become trillions of cells requires upwards energy levels, NOT downwards. Therefore, biological processes do adhere to the laws of physics and a cell or group of cells could never become a fully formed human.