Neuroscience: Idle minds

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Neuroscientists are trying to work out why the brain does so much when it seems to be doing nothing at all.


For volunteers, a brain-scanning experiment can be pretty demanding. Researchers generally ask participants to do something — solve mathematics problems, search a scene for faces or think about their favoured political leaders — while their brains are being imaged.

But over the past few years, some researchers have been adding a bit of down time to their study protocols. While subjects are still lying in the functional magnetic resonance imaging (fMRI) scanners, the researchers ask them to try to empty their minds. The aim is to find out what happens when the brain simply idles. And the answer is: quite a lot.

Some circuits must remain active; they control automatic functions such as breathing and heart rate. But much of the rest of the brain continues to chug away as the mind naturally wanders through grocery lists, rehashes conversations and just generally daydreams. This activity has been dubbed the resting state. And neuroscientists have seen evidence that the networks it engages look a lot like those that are active during tasks.

Resting-state activity is important, if the amount of energy devoted to it is any indication. Blood flow to the brain during rest is typically just 5–10% lower than during task-based experiments1. And studying the brain at rest should help to show how the active brain works. Research on resting-state networks is helping to map the brain’s intrinsic connections by showing, for example, which areas of the brain prefer to talk to which other areas, and how those patterns might differ in disease.

But what is all this activity for? Ask neuroscientists — even those who study the resting state — and many will sigh or shrug. “We’re really at the very beginning. It’s mostly hypotheses,” says Amir Shmuel, a brain-imaging specialist at McGill University in Montreal, Canada. Resting activity might be keeping the brain’s connections running when they are not in use. Or it could be helping to prime the brain to respond to future stimuli, or to maintain relationships between areas that often work together to perform tasks. It may even consolidate memories or information absorbed during normal activity.

“There’s so much enthusiasm about the approach now, and so little basic understanding,” says Michael Greicius, a neuroscientist at Stanford University in California, who started studying resting-state networks a decade ago.

Always active

A set of experiments in the mid-1990s first suggested that the brain never really takes a break. Bharat Biswal, then a PhD student at the Medical College of Wisconsin in Milwaukee, was trying to find ways of identifying and removing background signals from fMRI scans, in the hope that it would improve interpretations of the signals from tasks. “The assumption was, it was all noise,” says Biswal, who is now a biomedical engineer at the New Jersey Institute of Technology in Newark. But when he looked at scans taken when people were resting in the scanner, he saw regular, low-frequency fluctuations in the brain. Biswal’s experiments suggested that neuronal activity was causing these fluctuations.

Written By: Kerri Smith
continue to source article at nature.com

10 COMMENTS

  1. Is resting-state of a brain, also, when we sleep? If so, I
    would not be surprised that brain is releasing retained energy. All that energy
    we have raised to perform a certain action, but due to certain circumstances we
    could not. Energy, according to the first and the second law of thermodynamics
    must always do the work. What happens to the energy that we raised and we could
    not use, because we suppressed it? I suppose that (in a state when the brain
    relaxes), it simply releases accumulated and unused energy.

  2. Dan Dennett once said that trying to figure out how the brain works by using an MRI scanner is like trying to figure out how a chess computer works by using a voltmeter, and is pretty useless. Has the science actually progressed beyond the observation that for some thoughts, some coarse out-of-focus pattern in the brain lights up? Anyone could have guessed that that would happen. So what? To figure out how the brain really works without doing brain surgery I think we need fewer MRI technicians and more Derren Browns.

  3.  

    Is resting-state of a brain, also, when we sleep? 

    The brain is running at about 20% when you sleep.

    What happens to the energy that we raised and we couldnot use, because we suppressed it? 

    It leaves as heat, through conduction, convection, evaporation and  radiation. Your head is warm even when you are asleep. 
    Because heat goes out from the head due to the the brains activity, and the body looking after it, blood flow, hence the reason for the auld wives tail of wearing a hat to help keep warm.

    “Warm blooded animals control their body temperature by balancing heat production (from cell function) and heat loss (to the environment). Cold surroundings do lots of sneaky things to steal the heat from your body. If you come in direct contact with a cold object, like sitting on a snowy hill, you lose heat conduction. (Conduction is the process that causes heat transfer when two objects are touching each other – in this case, the snowy hill and your butt.) If you come in contact with cold air, you lose heat through convection. (Convection is the process that causes heat transfer when a gas moves past an object – in this case, cold air moving across your skin.) There is even something called the “chimney effect” that can work against you. Dense, cold air works its way into your pants and sleeves and pushes warm, light air out through other openings. Wind also works through convection, which is why blustery, cold days are the worst.”

    But generally, I think most of the energy from the brain dissipates through radiation.

  4.  Sorry, small insignificant point, I suck, but I’m pretty sure a cold breeze is stealing heat energy through conduction still, air molecules touch your skin steal a bit of energy and then get replaced with another cool air molecule. Convection is more the act of heat rising (less dense, rises above denser cool air/liquid). Radiators like the ones hung on walls are really convection heaters, only a small percentage of heat is radiated out into the room, the rest of it rises out the top towards the roof and cool air gets sucked up from the floor creating an air current that with a bit of time heats up the room. That’s why you shouldn’t put yer wet clobber on the radiator. Not at all fascinating but hey.

  5. “Radiation: Radiation of heat via electromagnetic waves is the body’s most efficient cooling. It accounts for 50-65% of heat loss. Radiation functions as long as there is a temperature difference between the air and the body. Radiation functions opposite, but is mainly the absorption of EM waves through UV radiation. Radiation ceases functioning on or near 95F (35C) “

    http://www.engineeringtoolbox…. 

    …as opposed to..

    “Convection: The body’s contact with the air around it creates heat dissipation through convection currents (breezes, wind, etc). The opposite is also true, when the temperature is hotter than the body’s temperature, the body will absorb heat energy. Core body temperatures for athletes in good shape and hydration increase at approx 1c/h without additional fluid intake. Convection accounts for 5-10% of the body’s heat loss. “

    …which is different to…

    “Conduction: If the body is in contact with anything cooler than it (such as clothing) heat is shed into the object. However, the opposite is also true – if the body is in contact with an object hotter than it your body will absorb some of the heat energy. This accounts for 2-5% of the body’s heat loss. “

    http://www.wisc-online.com/Obj

    …then there is…

    Evaporation: Evaporation of sweat and saliva accounts for 30-35% of the body’s heat loss. Evaporation ceases to be effective at 100% humidity. 

  6. “(Convection is the process that causes heat transfer when a gas moves
    past an object – in this case, cold air moving across your skin.)”

    This was the part that made me want to comment, that’s not what I learned at school. I’ll take my engineering tutor over a sports science type any day of the week. All in good taste mind. It’s likely just worded badly and should read “Convection causes an air current to occur enabling more heat transfer via conduction.” Well whatever, it was suitably vague enough to make me sperge all over the internet.

  7. I wish I could remember the number, but the brain burns a surprisingly high percentage of the body’s calories. Having a brain has to pay the freight for that by making us more efficient calorie gatherers.

  8. Lovely words about our physiology. I was wondering about this words in article:

    “But much of the rest of the brain continues to chug away as the mind naturally wanders through grocery lists, rehashes conversations and just generally daydreams. This activity has been dubbed the resting state. And neuroscientists have seen evidence that the networks it engages look a lot like those that are active during tasks”. and: “It may even consolidate memories or information absorbed during normal activity”.

    I understand that our brain connections work processing informations  when we are idle, or sleep, in same way as we are awake. What informations are being processed? Processing means using energy isn’t it? Energy is the ability of performing an action. I was thinking that brain is possibly working on retained informations that didn’t serve immediately when they have arisen in our brain as an idea. In resting state brain is perhaps discharge energy of retained informations. :)

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