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Nervous system

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"Thanks for the memories, but I'd prefer a bite to eat."

UFL.edu

As the organ responsible for maintaining equilibrium in the body and the most energy-demanding of all the organs, the brain takes a lot of the body's energy allocation. So when food is in short supply, the brain is the organ that is fed first. But what happens when there isn’t enough food to fulfill the high-energy needs of the brain and survival is threatened?

The brain does not simply self-allocate available resources on the fly; instead it “trims the fat” by turning off entire processes that are too costly. Researchers from CNRS in Paris created a true case of do-or-die, starving flies to the point where they must choose between switching off costly memory formation or dying. When flies are starved, their brains will block the formation of aversive long-term memories, which depend on costly protein synthesis and require repetitive learning.

But that doesn't mean all long-term memories are shut down. Appetitive long-term memories, which can be formed after a single training, are enhanced during a food shortage.

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Pyramidal neurons have a distinctive shape and set of connections.

Gao lab, Drexel

The cerebral cortex—the gray matter that forms the outer layers of the mammalian cerebrum and cerebellum—is divided into six different layers based on the presence of specialized neurons, and we've known that since the early 1900s. Denis Jabaudon is interested in using the tools of modern biology to understand the genetic mechanisms that establish and maintain those layers. Over the past few years, his lab has published papers implicating various genes in the generation of specific neuronal subtypes.

Now they have gone a step further. They have developed a new electrochemical method to transfer genes into specific types of neurons—they call it iontoporation. Using it, they have transformed one type of neuron in a mature brain into a different type entirely. (Imagine a lightning bolt and crash of thunder here to indicate how momentous and scary this is.) Just kidding—it’s not actually scary. Instead, it tells us something about the ability of a mature brain to adapt to being rewired.

Although Jabaudon and others have made some headway in working out how the different neurons arise, they still don’t know how plastic they are—if they can change fates after they started differentiating down one particular path. In the context of brain injury, it would be useful to know if certain neural circuits could be reprogrammed and repaired by having the neurons that are already present change fates to adapt to the damage. But this has been challenging to determine, because changing the fate of specific neurons in the latter stages of differentiation has been technically difficult.

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A cartoon showing spikes of activity traveling among neurons.

UC Berkeley

Computing hardware is composed of a series of binary switches; they're either on or off. The other piece of computational hardware we're familiar with, the brain, doesn't work anything like that. Rather than being on or off, individual neurons exhibit brief spikes of activity, and encode information in the pattern and timing of these spikes. The differences between the two have made it difficult to model neurons using computer hardware. In fact, the recent, successful generation of a flexible neural system required that each neuron be modeled separately in software in order to get the sort of spiking behavior real neurons display.

But researchers may have figured out a way to create a chip that spikes. The people at HP labs who have been working on memristors have figured out a combination of memristors and capacitors that can create a spiking output pattern. Although these spikes appear to be more regular than the ones produced by actual neurons, it might be possible to create versions that are a bit more variable than this one. And, more significantly, it should be possible to fabricate them in large numbers, possibly right on a silicon chip.

The key to making the devices is something called a Mott insulator. These are materials that would normally be able to conduct electricity, but are unable to because of interactions among their electrons. Critically, these interactions weaken with elevated temperatures. So, by heating a Mott insulator, it's possible to turn it into a conductor. In the case of the material used here, NbO2, the heat is supplied by resistance itself. By applying a voltage to the NbO2 in the device, it becomes a resistor, heats up, and, when it reaches a critical temperature, turns into a conductor, allowing current to flow through. But, given the chance to cool off, the device will return to its resistive state. Formally, this behavior is described as a memristor.

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The red tendrils represent Cthulhu's dreams

Commissioned to accompany the Brains: The Mind as Matter exhibition at the Wellcome Collection, Axon looks a little like flOw, except it’s much more hectic, with short games and high scores.

The game challenges players to grow their neuron as long as possible; climbing through brain tissue, out-competing rival neurons and creating as many connections to distant regions of the brain as they can.

This involves clicking on nodes in an effort to climb higher and higher. A speedy mouse finger is essential as a rapidly shrinking sphere marks the areas that are accessible and once no unclaimed nodes are within it, it’s gameover. Brain freeze. Play it here and read more (silly) below and (clever) here.

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Some commentary on a recently published article which has reported that frequent game players brain's can differ in structure and activation from infrequent players.

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Game/Mental State is an article series that looks at how and why mental states can be interpreted from game states. In other words, we're looking into our minds by looking into the game.

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Game/Mental Sate is an article series that looks at how and why mental states can be interpreted from game states. In other words, we're looking into our minds by looking into the game.

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iwdrm:

“I have all the characteristics of a human being: flesh, blood, skin, hair … but not a single, clear, identifiable emotion, except for greed and disgust.”

American Psycho (2000)

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