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Tuesday, 24 February 2009

The discovery of the "self" and the memory stored in our genes

Today:

  1. The secret life of the brain
  2. Goldmine bug DNA may be key to alien life
  3. Scientists create working artificial nerve networks
  4. Can experiences be passed on to offspring?
A truly amazing set of articles. I suggest you read them, I carefully shortened them, but the originals are even more informative. Read also my comments and please tell me what you think. Because I'm simply overwhelmed by joy and excitement. That kind of articles are precisely why this blog exists!

The secret life of the brain

IN 1953 Louis Sokoloff found out that although the brain accounting for 2% body mass consumes 20% of the calories we eat, it consumed no more oxygen while doing arithmetic than it did while he was resting with his eyes closed.

Marcus Raichle, a neuroscientist at Washington University in St Louis and colleagues discovered what the idling brain is doing. And whatever it does, it fires up whenever the brain is otherwise unoccupied and burns white hot, guzzling more oxygen, gram for gram, than your beating heart.

Raichle and Shulman published a paper in 2001 suggesting that they had stumbled onto a previously unrecognised "default mode" - an activity which the brain turns to when unoccupied and sets aside when called on to do something else. This brain activity occurred largely in a cluster of regions arching through the midline of the brain, from front to back-the default network.

Measurements of metabolic activity showed that some parts of this network devoured 30 per cent more calories than nearly any other area of the brain.

One of the core components is the medial prefrontal cortex , which is known to evaluate things from a highly self-centred perspective of whether they're likely to be good, bad, or indifferent. Parts of the default network also have strong connections to the hippocampus, which records and recalls autobiographical memories.

To Raichle and his colleague Debra Gusnard, this all pointed to one thing: daydreaming. Raichle and Gusnard speculated that the default network might provide the brain with an "inner rehearsal" for considering future actions and choices. So important is this exercise, it seems, that the brain engages in it whenever possible.

But people are starting to suspect that the default network does more than just daydream. In 2003 Michael Greicius of Stanford University in California studied the default network of calm patients with an fMRI scanner. This led him to find what are called resting state fluctuations in the default network - slow waves of neural activity that ripple through in a coordinated fashion, linking its constellation of brain areas into a coherent unit. The waves lasted 10 to 20 seconds from crest to crest, up to 100 times slower than typical EEG brain waves recorded by electrodes on the scalp.

Raichle reported last year that the network's resting waves continued in heavily anaesthetised monkeys as though they were awake. More recently, Greicius reported a similar phenomenon in sedated humans, and other researchers have found the default network active and synchronised in early sleep.

Raichle now believes that the default network is involved, selectively storing and updating memories based on their importance from a personal perspective. source

My comment: Ok, I couldn't shorten it more than this. But this article is extremely important. Why? Because it found out that the daydreaming is really important not only to us, but also for our brain. It a link between brain and personality in a way. What's more important is that they caught the origin of the "self". At least that's what I think those slow ripples are. Because when you daydream, you usually forget yourself, but at some points, something brings back the feeling of self, of being. I think that's what they found! Awesome!

Goldmine bug DNA may be key to alien life

A bug discovered deep in a goldmine and nicknamed "the bold traveller" has got astrobiologists buzzing with excitement. Its unique ability to live in complete isolation of any other living species suggests it could be the key to life on other planets.

A community of the bacteria Candidatus Desulforudis audaxviator has been discovered 2.8 kilometres beneath the surface of the Earth in fluid-filled cracks of the Mponeng goldmine in South Africa. Its 60 °C home is completely isolated from the rest of the world, and devoid of light and oxygen.

Dylan Chivian of the Lawrence Berkeley National Laboratory, California, studied the genes found in samples of the fluid to identify the organisms living within it, expecting to find a mix of species. Instead, he found that 99.9% of the DNA belonged to one bacterium, a new species. The remaining DNA was contamination from the mine and the laboratory.

A community of a single species is almost unheard of in the microbial world. It means the ecosystem's only species must extract everything it needs from an otherwise dead environment.

Chivian's analysis shows that D. audaxviator gets its energy from the radioactive decay of uranium in the surrounding rocks. It has genes to extract carbon from dissolved carbon dioxide and other genes to fix nitrogen, which comes from the surrounding rocks. Both carbon and nitrogen are essential building blocks for life as we know it, and are used in the building blocks of proteins, amino acids. D. audaxviator has genes to produce all the amino acids it needs.

D. audaxviator can also protect itself from environmental hazards by forming endospores - tough shells that protect its DNA and RNA from drying out, toxic chemicals and from starvation. It has a flagellum to help it navigate.

"One question that has arisen when considering the capacity of other planets to support life is whether organisms can exist independently, without access even to the Sun," says Chivian. "The answer is yes and here's the proof." source

My comment:Another stunningly cool discovery. At first I thought this organism must be alien, but the article suggest it could evolve from Earth bacteria with some luck and enough time. In any case, this bug is a proof that life can exist in much more variety than we usually assign to it. They guy lives on radioactivity! That's simply amazing.

Scientists create working artificial nerve networks

January 28th, 2009

Scientists have already hooked brains directly to computers by means of metal electrodes. In the future, the interface between brain and artificial system might be based on nerve cells grown for that purpose. In research that was recently featured on the cover of Nature Physics, Prof. Elisha Moses of the Physics of Complex Systems Department and his former research students Drs. Ofer Feinerman and Assaf Rotem have taken the first step in this direction by creating circuits and logic gates made of live nerves grown in the lab.

When neurons - brain nerve cells - are grown in culture, they don't form complex 'thinking' networks. Moses, Feinerman and Rotem wondered whether the physical structure of the nerve network could be designed to be more brain-like. To simplify things, they grew a model nerve network in one dimension only - by getting the neurons to grow along a groove etched in a glass plate. The scientists found they could stimulate these nerve cells using a magnetic field.

Experimenting further with the linear set-up, the group found that varying the width of the neuron stripe affected how well it would send signals. The researchers identified a threshold thickness, one that allowed the development of around 100 axons.

The scientists then took two thin stripes of around 100 axons each and created a logic gate similar to one in an electronic computer. Both of these 'wires' were connected to a small number of nerve cells. When the cells received a signal along just one of the 'wires,' the outcome was uncertain; but a signal sent along both 'wires' simultaneously was assured of a response. This type of structure is known as an AND gate. The next structure the team created was slightly more complex: Triangles fashioned from the neuron stripes were lined up in a row, point to rib, in a way that forced the axons to develop and send signals in one direction only. Several of these segmented shapes were then attached together in a loop to create a closed circuit. The regular relay of nerve signals around the circuit turned it into a sort of biological clock or pacemaker.

For the scientific paper, please see: http://www.nature.com/nphys/journal/v4/n12/pdf/nphys1099.pdf . source

My comment: Nice, huh?! Not simply nice, it's actually beautiful. Just imagine hooking up to your brain a neural interface that consists of neurons. Any idea for more gentle and natural way to link something to your head? This discovery has a lot of potential.

Can experiences be passed on to offspring?

It seems that in mice at least, mothers that receive mental training before they become pregnant can pass on its cognitive benefits to their young.

Previous studies in both people and animals have shown that a mother's experiences while pregnant can affect her offspring's gene expression and health, even years later.

Larry Feig at Tufts University School of Medicine in Boston and his colleagues bred "knockout" mice that lacked a gene called Ras-GRF-2, causing them to have a memory defect. Normally, if mice in a cage receive a shock to their feet, they freeze in fear if they are then placed back into the same cage. In contrast, Ras-GRF2 knockout mice did not associate the cage with fear.

Before they reached adolescence, the team kept these knockout mice in a cage filled with toys for two weeks. Such "enriched environments" are known to enhance learning and memory. In the knockout mice, the enriched cage was enough to compensate for their memory defect: when tested on the fear task, they associated the shock with the cage, like normal mice.

To see if this compensation could be passed on to young, the researchers waited for these enriched knockout mice to reach sexual maturity, bred them and tested their offspring on the fear task. Despite being reared by an "unenriched" knockout foster mother - to rule out the effects of spending time with a mouse they could learn directly from - the offspring associated the electric shock with the cage, just like their enriched mothers and those without the genetic defect.

In contrast, the offspring of knockout mice who did not receive the enrichment did not associate the shock with the cage (Journal of Neuroscience, DOI: 10.1523/jneurosci.5057-08.2009).

This effect was only seen in offspring whose knockout mothers had an enriched cage: having an enriched knockout father but a normal knockout mother was not enough to remedy the defect in the offspring.

As the offspring had the same genetic defect as their mothers, the researchers attribute the enhanced cognition in these mice to the time their mothers spent in the enriched cage prior to becoming pregnant.

The effect was not passed on to a third generation and was only inherited if the offspring were conceived within three months of enrichment. So the researchers suspect that the mother passes on this cognitive effect during gestation, perhaps by releasing hormones that prompt "epigenetic" chemical markers to appear on her unborn child's genes, regulating their expression after birth. source

My comment: I knew that even before that experiment, but I'm glad that now other people know it too. Again, this is stunning result. Why? Because it gives you the real value of your DNA. It's not simply a bunch of letters telling your body how to grow. It actually tells you much more-it can tell you about the problems of your ancestors, about important lessons learnt by your parents. Now, I'm not overestimating the implications-this effect is hard to catch. I think it only happens when the environment is close to the original situation or when you're in certain mind-state. Our brain constantly offers us all kind of sensors and voices, but we only choose what we're familiar with-that means that even if your internal memories warn you on something, you might very well not choose to accept that information. And this could happen almost subconsciously. But if you choose to stay concious the most, you might find very interesting information all around you. That's sooooo exciting!

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