Understanding how memories are stored

Bishadi · Mar 7, 2012

In one of the most basic proposals, a single atom or molecule acts as a quantum bit that processes signals that have been delivered via single photons. In the past twenty years scientists have shown that single molecules can be detected and single photons can be generated. However, excitation of a molecule with a photon had remained elusive because the probability that a molecule sees and absorbs a photon is very small. As a result, billions of photons per second are usually impinged on a molecule to obtain a signal from it.

One common way to get around this difficulty in atomic physics has been to build a cavity around the atom so that a photon remains trapped for long enough times to yield a favorable interaction probability. Scientists at ETH Zurich and Max Planck Institute for the Science of Light in Erlangen have now shown that one can even interact a flying photon with a single molecule. Among many challenges in the way of performing such an experiment is the realization of a suitable source of single photons, which have the proper frequency and bandwidth. Although one can purchase lasers at different colors and specifications, sources of single photons are not available on the market.

So a team of scientists led by Professor Vahid Sandoghdar made its own. To do this, they took advantage of the fact that when an atom or molecule absorbs a photon it makes a transition to a so-called excited state. After a few nanoseconds (one thousand millionth of a second) this state decays to its initial ground state and emits exactly one photon. In their experiment, the group used two samples containing fluorescent molecules embedded in organic crystals and cooled them to about 1.5 K (-272 °C). Single molecules in each sample were detected by a combination of spectral and spatial selection.

To generate single photons, a single molecule was excited in the source sample. When the excited state of the molecule decayed the emitted photons were collected and tightly focused onto the target sample at a distance of a few meters. To ensure that a molecule in that sample sees the incoming photons, the team had to make sure that they have the same frequency. Furthermore, the precious single photons had to interact with the target molecule in an efficient manner. A molecule is about one nanometer is size (100000 times smaller than the diameter of a human hair) but the focus of a light beam cannot be smaller than a few hundred nanometers.

This usually means that most of the incoming light goes around the molecule, i.e. without them seeing each other. However, if the incoming photons are resonant with the quantum mechanical transition of the molecule, the latter acts as a disk that is comparable to the area of the focused light. In this process the molecule acts as an antenna that grabs the light waves in its vicinity. The results of the study published in Physical Review Letters provide the first example of long-distance communication between two quantum optical antennas in analogy to the 19th century experiments of Hertz and Marconi with radio antennas. In those early efforts, dipolar oscillators were used as transmitting and receiving antennas.

In the current experiment, two single molecules mimic that scenario at optical frequencies and via a nonclassical optical channel, namely a single-photon stream. This opens many doors for further exciting experiments in which single photons act as carriers of quantum information to be processed by single emitters
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http://www.sciencedaily.com/releases/2012/02/120228101712.htm

Now combine that with an inquiry: how is a memory is stored upon mass?

You now can understand it

If you want to look for an old paper of 82', Photo Neuron Conduction (PNC)

resonant energy transfer between the synaptic connections

Bishadi · Jun 13, 2012

is that Holey Gold ?

Bishadi · May 7, 2013

old stuff

Bishadi8th January 2011, 11:10 AM
http://en.wikipedia.org/wiki/Stanford_R._Ovshinsky#The_Ovitron

The Ovitron

By the late 1950s, working at General Automation, Ovshinsky brought together these disparate studies in an invention. Crossing scientific disciplines that academics traditionally hold separate, including neurophysiology and cybernetics, Stan invented and Herb Ovshinsky helped build a mechanical model of a nerve cell, an amorphous thin-film switch they called the Ovitron. Stan patented the device and the brothers disclosed it publicly in 1959 in New York City. In an attempt to model the learning ability of nerve cells, which Stan recognized as deriving from the plasticity of the cell's membrane, he drew on his knowledge of surfaces and materials to fashion very thin layers of amorphous material, thus pioneering the use of nanostructures. He created these layers by combining elements, especially from the Group 16 elements....

It's all about the "O".

The guy is the namesake of Ovonics (A company that patented the intercalation of hydrogen; energy storage into fixed structures)

I didn't know he had a neurology foundation of personal studies.

How many are familiar with intercalation?

How many ever considered the idea that brain memories could be affixed to a structure (film)? Basically creating a memory to a fixed structure like a transparent lense?

Who can find that Ovitron Switch?

Bishadi · May 15, 2013

current

the glial is being missused here

Mice with human cells grafted into their brains outperform their normal counterparts on tests of learning and memory, according to new research. The findings, published today in the journal Cell Stem Cell, suggest that evolution of the human brain involved a major upgrade to long-neglected cells called astrocytes, and could provide a better way of testing potential treatments for neurological and psychiatric diseases.

Traditionally, our remarkable mental abilities were thought to come down to the massive expansion of the brain relative to body size during the course of evolution. We now know that size isn't everything, however, and some researchers have shifted their focus away from the brain's overall size and shape to study its microscopic structure instead, the idea being that human brain evolution involved specializations at the cellular level.

One such specialization was the emergence of entirely new type of cells. For example, the brains of humans and other great apes (as well as those of elephants and some whale and dolphin species) contain large cells called von Economo neurons, which aren't found in mice or other non-primate mammals. Another was an increase in the complexity of existing cell types, and astrocytes in particular have undergone numerous changes during human brain evolution.

Astrocytes are one of several types of glia, the non-neuronal cells found alongside neurons in the nervous system. Glial cells were discovered at around the same time as neurons, but were quickly dismissed as little more than support cells that insulate neurons, provide them with nourishment, and fill the spaces between them like polystyrene packaging. In the past decade, though, astrocytes have come into their own as key players in brain function – we now that they form signalling networks and make important contributions to the brain's information processing capabilities by regulating the way neurons communicate with each other.

In 2009, husband-and-wife team Maiken Nedergaard and Steve Goldman of the University of Rochester Medical Centre in New York reported major differences between mouse astrocytes and those isolated from the brains of humans and chimps. They found that human astrocytes are not only about twenty times the size of the mouse cells, but also far more complex, with about ten times as many finger-like projections, which they use to contact other brain cells and blood vessels. Human cells also work more efficiently than those of mice, propagating internal signals about four times faster. What's more, the human brain contains subtypes of astrocytes that aren't found in mice, and the ratio of astrocytes to neurons is far bigger.

To investigate these species differences further, Nedergaard, Goldman and their colleagues isolated glial cell progenitors – the stem cells that generate astrocytes – from aborted human foetuses, labelled them with fluorescent green protein, and then grafted them into the brains of newborn mice. When the animals reached adulthood, the researchers examined their brains, and found that while most of the cells remained as undifferentiated progenitors, small numbers of them had matured into human astrocytes that integrated themselves into the mouse brain circuitry.

The researchers also found that the human cells enhanced the strengthening of synaptic connections in slices tissue from the hippocampus, a process that is widely thought to be critical for learning and the formation of new memories, and that this was associated with improved performance on various tests of learning and memory.

The mice endowed with human cells learned to associate a mild electric shock with a particular sound or location in their environment far more quickly than another group of animals which received grafts of mouse cells. They also learned their way through a maze about twice as fast, and were better at recognizing familiar objects when they were placed in unusual location.

"This is incredibly interesting work which strongly suggests that human astrocytes are indeed enhanced in their ability to control synapses compared to mouse astrocytes," says neurobiologist Ben Barres of Stanford University. He adds several caveats, however. "They have not shown that the astrocytes are expressing their normal gene profile, and the enhanced cognitive performance could be because of the persisting precursor cells."

Evolutionary neuroanatomist Todd Preuss of Emory University agrees that the findings are very interesting, but says it's not surprising to see such big differences in the function of human and mouse astrocytes. "It's consistent with comparative genomics research indicating that the molecular basis of synaptic plasticity was modified in human evolution," he says. "t's not clear that the effects are the specific result of engrafting human cells, [so] it would be interesting to see if the investigators would get the same effects, or effects of the same magnitude, by engrafting chimpanzee or macaque glia."

Nevertheless, the technique of grafting human cells into mouse brains could improve the way in which researchers test potential treatments for a host of neurological and psychiatric diseases. "We can also generate glial progenitor cells from human skin cells reprogrammed into induced pluripotent stem cells," says Goldman.

"As a result, we can now establish glial progenitor cells from individuals with brain diseases," he says, "and we have already established chimeric mice containing glia from patients with schizophrenia." Such chimeras would be better for evaluating new drugs as they because they would bear a much closer resemblance to humans than existing mouse models.

The findings also have implications for how brain research is done. The vast majority of astrocyte research is done using mice and rats, and has yielded important insights into the contributions of these cells to brain function. It now seems clear, however, that the capabilities of human astrocytes far exceed those of mice, and researchers cannot hope to properly understand them, or how their specializations contributed to human brain evolution, by restricting their work to mouse models.

"Unfortunately," says Preuss, "many neuroscientists are uncomfortable with open discussion of human specializations, for fear that the adequacy of their model animal will be called into question. This study shows how comparative research and experimental research can – and should – co-exist, and more research along these lines would be informative."

Reference: Han, X., et al. (2013). Forebrain Engraftment by Human Glial Progenitor Cells Enhances Synaptic Plasticity and Learning in Adult Mice. Cell Stem Cell, DOI: 10.1016/j.stem.2012.12.015
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waltky · May 25, 2013

Why we lose early memories...

Neuron growth in children 'leaves no room for memories'
24 May 2013 - The reason we struggle to recall memories from our early childhood is down to high levels of neuron production during the first years of life, say Canadian researchers.

The formation of new brain cells increases the capacity for learning but also clears the mind of old memories. The findings were presented to the Canadian Association of Neuroscience. An expert at City University in London said the mouse study called into question some psychological theories. Neurogenesis, or the formation of new neurons in the hippocampus - a region of the brain known to be important for learning and remembering, reaches its peak before and after birth. It then declines steadily during childhood and adulthood. Dr Paul Frankland and Dr Sheena Josselyn, from the Hospital for Sick Children in Toronto and the University of Toronto, wanted to find out how the process of new neuron generation impacted on memory storage. They carried out their research on younger and older mice in the lab.

Early amnesia

In adult mice, they found that increasing neurogenesis after memory formation was enough to bring about forgetting. In infant mice, they discovered that decreasing neurogenesis after memory formation meant that the normal forgetting observed at this age did not occur. Their research suggests a direct link between a reduction in neuron growth and increased memory recall. They found the opposite to be true also - a decreased ability to remember when neurogenesis is increased (as happens during infancy). The researchers said this provided an explanation for the absence of long-term memory events from early childhood, known as infantile amnesia. Previous studies have shown that although young children can remember events in the short term, these memories do not persist.

Dr Frankland, senior scientist in neuroscience and mental health, at the hospital, said: "Why infantile amnesia exists has long been a mystery. "We think our new studies begin to explain why we have no memories from our earliest years. "Before the ages of four or five, we have a highly dynamic hippocampus which can't stably store information. "As new neurons are generated, memory may be compromised by that process."

Dr Bettina Forster, from the cognitive neuroscience research unit at City University in London, said the research showed a clear link. "This is a very interesting and elegantly executed study which shows a direct link between neurogenesis and memory formation. "The results questions the long assumed link between verbal development and infantile amnesia and calls into question some psychological and psychotherapeutic theories on this topic."

http://www.bbc.co.uk/news/health-22639040
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Bishadi · May 27, 2013

glial.....

take my word for it

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