Psychologists Use fMRI To Understand Ties Between Memories And The Imagination
ScienceDaily.com — Psychologists have found that thought patterns used to recall the past and imagine the future are strikingly similar. Using functional magnetic resonance imaging to show the brain at work, they have observed the same regions activated in a similar pattern whenever a person remembers an event from the past or imagines himself in a future situation. This challenges long-standing beliefs that thoughts about the future develop exclusively in the frontal lobe.
Remembering your past may go hand-in-hand with envisioning your future! It’s an important link researchers found using high-tech brain scans. It’s answering questions and may one day help those with memory loss.
For some, the best hope of ‘seeing’ the future leads them to seek guidance — perhaps from an astrologist. But it’s not very scientific. Now, psychologists at Washington University are finding that your ability to envision the future does in fact goes hand-in-hand with remembering the past. Both processes spark similar neural activity in the brain.
“You might look at it as mental time travel–the ability to take thoughts about ourselves and project them either into the past or into the future,” says Kathleen McDermott, Ph.D. and Washington University psychology professor. The team used “functional magnetic resonance imaging” — or fMRI — to “see” brain activity. They asked college students to recall past events and then envision themselves experiencing such an event in their future. The results? Similar areas of the brain “lit up” in both scenarios.
“We’re taking these images from our memories and projecting them into novel future scenarios,” says psychology professor Karl Szpunar.
Most scientists believed thinking about the future was a process occurring solely in the brain’s frontal lobe. But the fMRI data showed a variety of brain areas were activated when subjects dreamt of the future.
“All the regions that we know are important for memory are just as important when we imagine our future,” Szpunar says.
Researchers say besides furthering their understanding of the brain — the findings may help research into amnesia, a curious psychiatric phenomenon. In addition to not being able to remember the past, most people who suffer from amnesia cannot envision or visualize what they’ll be doing in the future — even
the next day.
An MRI image depicts a scan of a normal human brain. A new study has shown that a computer program can match scans of brain activity with visual images and even predict what people are seeing. Image courtesy NIH/NIDA
BACKGROUND: Researchers from Washington University in St. Louis have used advanced brain imaging techniques to show that remembering the past and envisioning the future may go hand-in-hand, with each process showing strikingly similar patterns of activity within precisely the same broad network of brain regions. This suggests that envisioning the future may be a critical prerequisite for many higher-level planning processes in the brain.
WHAT IS fMRI: Magnetic resonance imaging (MRI) uses radio waves and a strong magnetic field rather than X-rays to take clear and detailed pictures of internal organs and tissues. fMRI uses this technology to identify regions of the brain where blood vessels are expanding, chemical changes are taking place, or extra oxygen is being delivered. These are indications that a particular part of the brain is processing information and giving commands to the body. As a patient performs a particular task, the metabolism will increase in the brain area responsible for that task, changing the signal in the MRI image. So by performing specific tasks that correspond to different functions, scientists can locate the part of the brain that governs that function.
ABOUT THE STUDY: The researchers relied on fMRI to capture patterns of brain activation as college students were given 10 seconds to develop a vivid mental image of themselves or a famous celebrity participating in a range of common life experiences. Presented with a series of memory cues — such as getting lost, spending time with a friend, or attending a birthday party — participants were asked to recall a related event from their own past; to envision themselves experiencing such an event in their future life; or to picture a famous celebrity (specifically, former U.S. president Bill Clinton) participating in such an event.
WHAT THEY FOUND: Comparing images of brain activity in response to the ‘self-remember’ and ‘self future’ event cues, researchers found a surprisingly complete overlap among regions of the brain used for remembering the past and those used for envisioning the future. The study clearly demonstrates that the neural network underlying future thoughts is not only happening in the brain’s frontal cortex. Although the frontal lobes play an important role in carrying out future-oriented operations — such as anticipation, planning and monitoring — the spark for these activities may be the process of envisioning yourself in a specific future event. And that’s an activity based on the same brain network used to remember memories about our own lives. Also, patterns of activity suggest that the visual and spatial context for our imagined future is often pieced together using our past experiences, including memories of specific body movements: data our brain has stored as we navigated through similar settings in the past.
New research suggests that circuits in the adult brain are continually modified by experience. (Credit: iStockphoto/Mark Evans)
PLoS, July 29, 2010 — The adult brain, long considered to be fixed in its wiring, is in fact remarkably dynamic. Neuroscientists once thought that the brain’s wiring was fixed early in life, during a critical period beyond which changes were impossible. Recent discoveries have challenged that view, and now, research by scientists at Rockefeller University suggests that circuits in the adult brain are continually modified by experience.
The researchers, led by Charles D. Gilbert, Arthur and Janet Ross Professor and head of the Laboratory of Neurobiology, observed how neurons responsible for receiving input from a mouse’s whiskers shift their relationships with one another after single whiskers are removed. The experiments explain how the circuitry of a region of the mouse brain called the somatosensory cortex, which processes input from the various systems in the body that respond to the sense of touch, can change.
The findings are published in the online, open access journal PLoS Biology.
The Gilbert lab has been studying changing neuronal connections for several years. Their approach, in which the scientists use a viral labeling system to attach fluorescent proteins to individual neurons and then image individual synapses in an intact, living brain with a high-resolution two-photon microscope, has provided several important clues to understanding the dynamics of the brain’s wiring.
Students in the Gilbert lab, Dan Stettler and Homare (Matias) Yamahachi, in collaboration with Winfried Denk at the Max Planck Institute in Heidelberg, previously followed the same neurons week after week in the primary visual cortex of adult monkeys. They found that the circuits of the visual cortex are highly dynamic, turning over synapses at a rate of seven percent per week. These changes occurred without any learning regimen or physical manipulations to the neurons. Last year, Yamahachi, together with Sally Marik and Justin McManus, showed that when sensory experience is altered, even more dramatic changes in cortical circuits occur, with very rapid alterations in circuitry involving an exuberant growth of new connections paralleled by a pruning of old connections.
These studies and others by the Gilbert lab have begun to show that there are underlying dynamics in the sensory cortex and it’s not a fixed system, as has long been believed.
In the new study, Marik and other members of the Gilbert lab looked at excitatory and inhibitory neurons within the mouse cortex during periods of sensory deprivation to determine how experience shapes different components of cortical circuitry. For this study they used the whisker-barrel system in adult mice. The barrel cortex, part of the somatosensory cortex, receives sensory input from the animal’s whiskers. Scientists have shown that after a row of whiskers is removed, barrels shift their representation to adjacent intact whiskers.
Marik, together with Yamahachi and McManus, found that after a whisker was plucked excitatory connections projecting into the deprived barrels underwent exuberant and rapid axonal sprouting. This axonal restructuring occurred rapidly — within minutes or hours after whiskers were plucked — and continued over the course of several weeks. At the same time that excitatory connections were invading the deprived columns, there was a reciprocal outgrowth of the axons of inhibitory neurons from the deprived to the non-deprived barrels. This suggests that the process of reshaping cortical circuits maintains the balance between excitation and inhibition that exists in the normal cortex.
“Previously we showed changes only in excitatory connections,” Gilbert says. “We’ve now demonstrated a parallel involvement of inhibitory connections, and we think that inhibition may play a role equal in importance to excitation in inducing changes in cortical functional maps.”
The new study also showed that changes in the inhibitory circuits preceded those seen in the excitatory connections, suggesting that the inhibitory changes may mediate the excitatory ones. This process, Gilbert says, mimics what happens in the brain during early postnatal development.
“It’s surprising that the primary visual or somatosensory cortices are involved in plasticity and capable of establishing new memories, which previously had been considered to be a specialized function of higher brain centers,” Gilbert says. “We are just beginning to tease apart the mechanisms of adult cortical plasticity. We hope to determine whether the circuit changes associated with recovery of function following lesions to the central and peripheral nervous systems also occur under normal conditions of perceptual learning.”
Source: Public Library of Science
- Marik SA, Yamahachi H, McManus JNJ, Szabo G, Gilbert CD. Axonal Dynamics of Excitatory and Inhibitory Neurons in Somatosensory Cortex. PLoS Biology, 2010; 8 (6): e1000395 DOI: 10.1371/journal.pbio.1000395
Public Library of Science (2010, June 16). Experience shapes the brain’s circuitry throughout adulthood.
Dendrites of a nerve cell in brain appear like branches of a tree. Left: A patch clamp pipette injects fluorescent dye into the cell. (Credit: Image courtesy of Technische Universitaet Muenchen)
ScienceDaily.com — Pioneering a novel microscopy method, neuroscientist Arthur Konnerth and colleagues from the Technische Universitaet Muenchen (TUM) have shown that individual neurons carry out significant aspects of sensory processing: specifically, in this case, determining which direction an object in the field of view is moving. Their method makes it possible for the first time to observe individual synapses, nerve contact sites that are just one micrometer in size, on a single neuron in a living mammalian brain.
Focusing on neurons known to play a role in processing visual signals related to movement, Konnerth’s team discovered that an individual neuron integrates inputs it receives via many synapses at once into a single output signal — a decision, in essence, made by a single nerve cell. The scientists report these results in the latest issue of the journal Nature. Looking ahead, they say their method opens a new avenue for exploration of how learning functions at the level of the individual neuron.
When light falls on the retina of the human eye, it hits 126 million sensory cells, which transform it into electrical signals. Even the smallest unit of light, a photon, can stimulate one of these sensory cells. As a result, enormous amounts of data have to be processed for us to be able to see. While the processing of visual data starts in the retina, the finished image only arises in the brain or, to be more precise, in the visual cortex at the back of the cerebrum. Scientists working with Arthur Konnerth — professor of neurophysiology at TUM and Carl von Linde Senior Fellow at the TUM Institute for Advanced Study — are interested in a certain kind of neuron in the visual cortex that fires electrical signals when an object moves in front of our eyes — or the eyes of a mouse.
When a mouse is shown a horizontal bar pattern in motion, specific neurons in its visual cortex consistently respond, depending on whether the movement is from bottom to top or from right to left. The impulse response pattern of these “orientation” neurons is already well known. What was not previously known, however, is what the input signal looks like in detail. This was not easy to establish, as each of the neurons has a whole tree of tiny, branched antennae, known as dendrites, at which hundreds of other neurons “dock” with their synapses.
To find out more about the input signal, Konnerth and his colleagues observed a mouse in the act of seeing, with resolution that goes beyond a single nerve cell to a single synapse. They refined a method called two-photon fluorescence microscopy, which makes it possible to look up to half a millimeter into brain tissue and view not only an individual cell, but even its fine dendrites. Together with this microscopic probe, they conducted electrical signals to individual dendrites of the same neuron using tiny glass pipettes (patch-clamp technique). “Up to now, similar experiments have only been carried out on cultured neurons in Petri dishes,” Konnerth says. “The intact brain is far more complex. Because it moves slightly all the time, resolving individual synaptic input sites on dendrites was extremely difficult.”
The effort has already rewarded the team with a discovery. They found that in response to differently oriented motions of a bar pattern in the mouse’s field of vision, an individual orientation neuron receives input signals from a number of differently oriented nerve cells in its network of connections but sends only one kind of output signal. “And this,” Konnerth says, “is where things get really exciting.” The orientation neuron only sends output signals when, for example, the bar pattern moves from bottom to top. Evidently the neuron weighs the various input signals against each other and thus reduces the glut of incoming data to the most essential information needed for clear perception of motion.
In the future, Konnerth would like to extend this research approach to observation of the learning process in an individual neuron. Neuroscientists speculate that a neuron might be caught in the act of learning a new orientation. Many nerve endings practically never send signals to the dendritic tree of an orientation neuron. Presented with visual input signals that represent an unfamiliar kind of movement, formerly silent nerve endings may become active. This might alter the way the neuron weighs and processes inputs, in such a way that it would change its preferred orientation; and the mouse might learn to discern certain movements better or more rapidly. “Because our method enables us to observe, down to the level of a single synapse, how an individual neuron in the living brain is networked with others and how it behaves, we should be able to make a fundamental contribution to understanding the learning process,” Konnerth asserts. “Furthermore, because here at TUM we work closely with physicists and engineers, we have the best possible prospects for improving the spatial and temporal resolution of the images.”
This work was supported by grants from Deutsche Forschungsgemeinschaft (DFG) and Friedrich-Schiedel-Stiftung.
Journal Reference: Hongbo Jia, Nathalie L. Rochefort, Xiaowei Chen, Arthur Konnerth. Dendritic organization of sensory input to cortical neurons in vivo. Nature, 2010; 464 (7293): 1307 DOI: 10.1038/nature08947
Technische Universitaet Muenchen (2010, April 30). Watching a living brain in the act of seeing — with single-synapse resolution.
GoogleNews.com, July 29, 2010, by Nicole Aber — Working in sales means dealing face-to-face with clients. So when Larry Webb looked in the mirror and noticed he looked “gaunt” due to aging, he began to feel inhibited in his career.
“I didn’t want people looking at my cheeks, but to look at my eyes,” Webb, 65, said.
So in an effort to gain a more youthful appearance, the Dallas man underwent Cell Enriched Cosmetic Surgery, an experimental procedure that transfers a combination of fat cells containing stem cells to other areas of the body .
The procedure was performed by Dr. Jeffrey Caruth, medical director of Plano Aesthetics in Plano, Texas, about three months ago, and it gave Webb more volume in his face to reverse the “aging and deterioration of muscle tissue in the cheeks,” Webb said.
The procedure is not yet approved by the Food and Drug Administration, but Caruth estimates it will be within six months. Stem cell fat transfers have been approved and performed in Europe for years, he said.
Cell Enriched Cosmetic Surgery, which Caruth began performing in March, involves removing fat cells from one or multiple parts of the body, treating the fat cells to multiply the amount of stem cells within them, and then transferring those stem cell-rich fat cells to the breasts, face, or other areas of the body to provide more volume and a longer-lasting result, Caruth told FoxNews.com.
Multiplying the stem cells by thousands, Caruth said, allows for a better survival rate of the transported fat cells in addition to helping “in the anti-aging process because the stem cells will promote better tissue regeneration and tissue healing.”
But some plastic surgeons are wary of the effectiveness of stem cells in these procedures and say not enough research has been done to prove their benefit in cosmetic surgery.
Dr. William Adams Jr., who practices in Dallas, said there is a lack of research in this area to prove that stem cells add any benefit to the regular fat transfer procedures, which plastic surgeons have been using for years.
“Although stem cell things is the sexy thing to talk about right now … the reality is that the science right now hasn’t necessarily shown that it’s any better than the standard technique,” Adams said.
In Webb’s case, Caruth removed fat cells from the abdomen and transferred them to his face. Webb said that appealed to him because it used something natural from his own body.
He said he has had no complications and would recommend the procedure “definitely for people that need it not only for their job, maybe possibly if they’re in sales, or for themselves and want to look the best they can.”
Advantages of the stem cell fat transfer procedure over other types of cosmetic surgeries on the market are the ability to use more volume of the fat cells than the popular, more expensive synthetic fillers like Resilin, and the longevity of the procedure – about five to 10 years, according to Caruth, who has performed about 20 to 25 of these autologous stem cell fat transfers.
And compared to other plastic surgeries, Caruth said, the stem cell fat transfers are much less invasive, as they are done using local anesthesia either through an outpatient procedure or right in the office.
But for a procedure that hasn’t been fully proven to be effective, Adams said the cost of these stem cell fat transfers is relatively expensive – about $3,000 more than standard fat transfer procedures. A face lift that uses the stem cell fat transfer costs about $6,500, while breast augmentation costs an average of $15,000, Caruth said.
#1 Gene for autoimmunity
Rare genetic variants in the protein sialic acid acetylesterase (SASE) are linked to common human autoimmune diseases, including type 1 diabetes, arthritis, and Crohn’s disease. In mice, defects in the protein have been linked to problems in B-cell signaling and the development of auto-antibodies.
I. Surolia, et al., “Functionally defective germline variants of sialic acid acetylesterase in autoimmunity,” Nature, 466:243-7. Epub 2010 Jun 16. Eval by Mark Anderson, UCSF Diabetes Center; Anthony DeFranco, University of California, San Francisco; Takeshi Tsubata, Tokyo Medical University, Japan.
#2 Cell mobility illuminated
Using light to activate a the protein Rac in a single cell, researchers show how the protein can induce a group of epithelial cells to polarize en masse, suggesting that these cells can sense movement as a group.
X. Wang, et al., “Light-mediated activation reveals a key role for Rac in collective guidance of cell movement in vivo,” Nat Cell Biol, 12:591-7. Epub 2010 May 16. Eval by Susan Hopkinson and Jonathan Jones, Northwestern University Medical School; Ekaterina Papusheva and Carl-Phillip Heisenberg, Max-Plank-Institute for Molecular Cell Biology and Genetics; Jonathan Chernoff, Fox Chase Cancer Center.
#3 How the brain communicates
Reproducing the electrical activity of the neurons in the mouse cortex, researchers demonstrate how different layers of the brain communicate to piece together information from a wide range of sensory inputs — a process that many neuroscientists consider a major mystery in the field.
H. Adesnik and M. Scanziani. “Lateral competition for cortical space by layer-specific horizontal circuits,” Nature, 464:1155-60, 2010. Eval by Aguan Wei and Jan-Marino Ramirez, University of Washington; James Cottam and Michael Hausser, University College London.
#4 Backwards-working neurons
Normally neurons respond strongly to synapses located closer to the cell’s center and weakly to those located on the cell’s tips. But the authors found that certain neurons important in spatial memory react more strongly to the distant brain signals than those from nearby neurons.
V. Chevaleyre and SA Siegelbaum. “Strong CA2 pyramidal neuron synapses define a powerful disynaptic cortico-hippocampal loop,” Neuron, 66:560-72, 2010. Eval byStephen M Fitzjohn and Graham Collingridge, MRC centre for Synaptic Plasticity; Johannes Hell, University of California, Davis.
#5 Cell-swallowing proteins
Researchers identify two proteins vital to — and perhaps responsible for initiating — the way eukaryotic cells take up ligands bound to the surface receptors into membrane-bound vesicles, a process essential for a vast number of cellular functions, including nutrient uptake, receptor signaling, pathogen entry, and drug delivery.
WM Henne, et al., ” FCHo proteins are nucleators of clathrin-mediated endocytosis,” Science, 328:1281-4, 2010. Eval by Martin Lowe, University of Manchester; Pekka Lappalainen, Institute of Biotechnology, Finland.
#6 Less genetic “dark matter”
In opposition to the idea that much of the mammalian genome is uselessly transcribed into non-functional RNA molecules, researchers demonstrate that there is relatively little RNA derived from the expanses of DNA in between functional genes.
H van Bakel et al., “Most ‘dark matter’ transcripts are associated with known genes,” PLoS Biol, 2010 May 18;8(5):e1000371. Eval by Daniel Reines, Emory University School of Medicine; Adnane Sellam and Andre Nantel, National Reseasrch Council of Canada.
#7 Death receptor helps cancer live
The apoptosis receptor DC95 that induces cell death may also promote cancer growth, providing a new possible target for cancer therapies.
L. Chen et al., “CD95 promotes tumour growth,” Nature, 465:492-6, 2010. Eval by Sharad Kumar, Centre for Cancer Biology, Austrailia; Astar Winoto, University of California, Berkeley.
The F1000 Top 7 is a snapshot of the highest ranked articles from a 30-day period on Faculty of 1000 Biochemistry, as calculated on July 8, 2010. Faculty Members evaluate and rate the most important papers in their field. To see the latest rankings, search the database, and read daily evaluations, visit http://f1000.com.
Jennifer Welsh contributed to this article.
Synthetic Biology is an emerging field. Much work still is to be done, but the progress already made points out to an exciting sci pathway.
Whether the applications of the Synth-Bio are conducted towards the production of new pharmaceutical products, or to the manufacturing of specialized biocomponents – that might help to reduce the contamination – it really, really has possibilities.
In a research conducted by Dr. Pamela Silver at the Harvard Medical School (HMS) a milestone was reached.
As every engineer knows, the design must be strongly tested before going on to the manufacturing issues. That makes it very close to the Maths models. In fact, if a new structure is to be built, an engineer would test the design FIRST, against some complex mathematical models that would output the resistance to pressure, tangential effort and aome other physical factors. After that, the process of building – let’s say a bridge – would include some considerations.
Silver et al, achieved successfully at inducing a memory loop in yeast cells and producing a new mathematical model that predicted – with a certain degree of accuracy – the behaviour of the cells.
The experiment was about including a pair of genes – synthetic – with the ability to produce transcription factors.
Transcription Factors are capable of regulating the activity of specific genes, forcing them to synthetize (or otherwise disable) a specific protein.
The first gene reacted to the presence of Galactose, producing a transcription factor, which in turn, activated the second gene. Then, the second gene reacted by producing a transcription factor, which at the end reactivated itself (the second gene). This caused a feedback loop, that was maintained by the presence of Galactose.
But, when the Galactose was extracted from the medium, then the first gene stopped producing its transcription factor, but the second gene continued producing its own.
The new cells – as expected – kept producing the second gene transcription factor and the experiment was successful.
“Essentially what happened is that the cell remembered that it had been
exposed to galactose, and continued to pass this memory on to its descendents,” says Ajo-Franklin, a co-worker of Dr. Silver. “So after many cell divisions, the feedback loop remained intact without galactose or any other sort of molecular trigger.”
Most important is that the construction phase was guided by the mathematical model. That has profound implications in the future of the Synthetic Biology.
If “black boxes” are to be constructed then it’s positively compulsory to be backed-up on the Mathematical models. Accuracy is needed as to foresee a future when black boxes would be plugged into living cells, knowing exactly what the results will be. The same way a Computer Technician plugs a memory chip into the appropriate mainboard slot of the PC.
Structure of DNA
Illustration of the double helical structure of the DNA molecule.
The structure of DNA is illustrated by a right handed double helix, with about 10 nucleotide pairs per helical turn. Each spiral strand, composed of a sugar phosphate backbone and attached bases, is connected to a complementary strand by hydrogen bonding (non- covalent) between paired bases, adenine (A) with thymine (T) and guanine (G) with cytosine (C).
Adenine and thymine are connected by two hydrogen bonds (non-covalent) while guanine and cytosine are connected by three.
This structure was first described by James Watson and Francis Crick in 1953.
Process whereby DNA encodes for the production of amino acids and proteins.
This process can be divided into two parts:
Before the synthesis of a protein begins, the corresponding RNA molecule is produced by RNA transcription. One strand of the DNA double helix is used as a template by the RNA polymerase to synthesize a messenger RNA (mRNA). This mRNA migrates from the nucleus to the cytoplasm. During this step, mRNA goes through different types of maturation including one called splicing when the non-coding sequences are eliminated. The coding mRNA sequence can be described as a unit of three nucleotides called a codon.
The ribosome binds to the mRNA at the start codon (AUG) that is recognized only by the initiator tRNA. The ribosome proceeds to the elongation phase of protein synthesis. During this stage, complexes, composed of an amino acid linked to tRNA, sequentially bind to the appropriate codon in mRNA by forming complementary base pairs with the tRNA anticodon. The ribosome moves from codon to codon along the mRNA. Amino acids are added one by one, translated into polypeptidic sequences dictated by DNA and represented by mRNA. At the end, a release factor binds to the stop codon, terminating translation and releasing the complete polypeptide from the ribosome.
One specific amino acid can correspond to more than one codon. The genetic code is said to be degenerate.
Simplified Diagram of Cellular Metabolism
The three stages of cellular metabolism lead from food to waste products in animal cells. This series of reactions produces ATP, which is then used to drive biosynthetic reactions and other energy-requiring processes in the cell. Stage 1 mostly occurs outside cells––although special organelles called lysosomes can digest large molecules in the cell interior. Stage 2 occurs mainly in the cytosol, except for the final step of conversion of pyruvate to acetyl groups on acetyl CoA, which occurs in mitochondria. Stage 3 occurs in mitochondria.
Biotechnology: Present and Future
Areas of applied biotechnology:
In 1885, a scientist named Roux demonstrated embryonic chick cells could be kept alive outside an animal’s body. For the next hundred years, advances in cell tissue culture have provided fascinating glimpses into many different areas such as biological clocks and cancer therapy.
Monoclonal antibodies are new tools to detect and localize specific biological molecules. In principle, monoclonal antibodies can be made against any macromolecule and used to locate, purify or even potentially destroy a molecule as for example with anticancer drugs.
Molecular biology is useful in many fields. DNA technology is utilized in solving crimes. It also allows searchers to produce banks of DNA, RNA and proteins, while mapping the human genome. Tracers are used to synthesize specific DNA or RNA probes, essential to localizing sequences involved in genetic disorders.
With genetic engineering, new proteins are synthesized. They can be introduced into plants or animal genomes, producing a new type of disease resistant plants, capable of living in inhospitable environments (i.e. temperature and water extremes,…). When introduced into bacteria, these proteins have also produced new antibiotics and useful drugs.
Techniques of cloning generate large quantities of pure human proteins, which are used to treat diseases like diabetes. In the future, a resource bank for rare human proteins or other molecules is a possibility. For instance, DNA sequences which are modified to correct a mutation, to increase the production of a specific protein or to produce a new type of protein can be stored . This technique will be probably play a key role in gene therapy.
The-Scientist.com, July 28, 2010, by Megan Scudellari
#1 Neurons complete hippocampus loop
There’s a new, important function for a once-obscure cell population in the brain: CA2 pyramidal neurons, a subset of cells in the hippocampus, form a link between electrical inputs and outputs in the hippocampus.
V. Chevaleye et al., “Strong CA2 pyramidal neuron synapses define a powerful disynaptic cortico-hippocampal loop,” Neuron, 66:560-72, 2010. Eval by Stephen Fitzjohn and Graham Collingridge, MRC Centre for Synaptic Plasticity, UK; Johannes Hell, University of California, Davis.
#2 Non-overlapping neurons
The medial entorhinal cortex, a hub for memory and navigation in the brain, consists of two tangled but functionally separate networks that have different long-range axonal targets, and thus may be involved in different functions in the brain. The finding offers insights to how neural networks function, and — in conditions like epilepsy — dysfunction.
C. Varga et al., “Target-selective GABAergic control of entorhinal cortex output,” Nat Neurosci, 13:822-4, 2010. Eval by Edvard Moser, Norwegian University of Science and Technology, Norway; Jeff Isaacson, University of California, San Diego.
#3 “We’re going to need a bigger model”
In a detailed mathematical analysis, researchers analyze the capacity of computational models to model neuronal oscillations — the repetitive rise and fall of membrane potentials. They find that current single-cell oscillation models are not adequate, and there is a need for additional computational models to assess this mechanism.
M.W. Remme et al., “Democracy-independence trade-off in oscillating dendrites and its implications for grid cells,” Neuron, 66:560-72, 2010. Eval by Lisa Giocomo and Edvard Moser, Norwegian University of Science and Technology, Norway; Neil Burgess, University College London.
#4 Key step to making dendrites
For the first time, researchers demonstrate that a protein that fuses membranes instructs the development of dendrites in C. elegans. The protein, EFF-1, causes overlapping branches to fuse together, a novel control mechanism for the poorly understood morphogenesis of dendrites.
M. Oren-Suissa et al., “The fusogen EFF-1 controls sculpting of mechanosensory dendrites,” Science, 328:1285-8, 2010. Eval by Tina Schwabe and Thomas Clandinin, Stanford University, California; Andrew Chisholm, University of California, San Diego.
#5 How amyloid kills synapses
New findings suggest an explanation for why amyloid causes synapses to fail in Alzheimer’s and other diseases: The binding of amyloid beta oligomers causes glutamate receptors in synaptic membranes to form clusters, resulting in increased intracellular calcium and eventual deterioration of the synapse.
M. Renner et al., “Deleterious effects of amyloid beta oligomers acting as an extracellular scaffold for mGluR5,” Neuron, 66:739-54, 2010. Eval by Joel Bockaert, Institute of Functional Genomics, France; Hui-Chen Lu and Kenneth Mackie, Indiana University.
#6 New mechanism for synaptic plasticity
Researchers have uncovered another key mechanism behind one of the most important processes in learning and memory, synaptic plasticity. Specifically, two signaling molecules, BRAG2 and Arf6, trigger endocytosis of AMPA receptors in the brain, inducing long-term depression (LTD), a long-lasting reduction in the sensitivity of neurons and a well-known form of synaptic plasticity.
R. Scholz et al., “AMPA receptor signaling through BRAG2 and Arf6 critical for long-term synaptic depression,” Neuron, 66:768-80, 2010. Eval by Stephen Fitzjohn and Graham Collingridge, MRC Centre for Synaptic Plasticity, UK; Johannes Hell, University of California, Davis.
#7 Cell division affects cell fate
Through live imaging of a zebrafish embryo, researchers show that asymmetrical cell division is important in establishing cell fate in the vertebrate central nervous system.
P. Alexandre et al., “Neurons derive from the more apical daughter in asymmetric divisions in the zebrafish neural tube,” Nat Neurosci, 13:673-9, 2010. Eval by Judith Eisen, University of Oregon; Caren Norden and William Harris, University of Cambridge, UK.
The F1000 Top 7 is a snapshot of the highest ranked articles from a 30-day period on Faculty of 1000 Neuroscience, as calculated on July 22, 2010. Faculty Members evaluate and rate the most important papers in their field. To see the latest rankings, search the database, and read daily evaluations, visit http://f1000.com.
UCLA, July 28, 2010 — The ability to tell time is fundamental to how humans interact with each other and the world. Timing plays an important role, for example, in our ability to recognize speech patterns and to create music.
Patterns are an essential part of timing. The human brain easily learns patterns, allowing us to recognize familiar patterns of shapes, like faces, and timed patterns, like the rhythm of a song. But exactly how the brain keeps time and learns patterns remains a mystery.
In this three-year study, UCLA scientists attempted to unravel the mystery by testing whether networks of brain cells kept alive in culture could be “trained” to keep time. The team stimulated the cells with simple patterns — two stimuli separated by different intervals lasting from a twentieth of a second up to half a second.
After two hours of training, the team observed a measurable change in the cellular networks’ response to a single input. In the networks trained with a short interval, the network’s activity lasted for a short period of time. Conversely, in the networks trained with a long interval, network activity lasted for a longer amount of time.
The UCLA findings are the first to suggest that networks of brain cells in a petri dish can learn to generate simple timed intervals. The research sheds light on how the brain tells time and will enhance scientists’ understanding of how the brain works.
The study was supported by a grant from the National Institute of Mental Health.
Source & Journal: Hope A Johnson, Anubhuthi Goel, Dean V Buonomano. Neural dynamics of in vitro cortical networks reflects experienced temporal patterns. Nature Neuroscience, 2010; DOI: 10.1038/nn.2579
FORBES.COM, July 28, 2010, by Seth Borenstein
WASHINGTON — Despite their tiny size, plant plankton found in the world’s oceans are crucial to much of life on Earth. They are the foundation of the bountiful marine food web, produce half the world’s oxygen and suck up harmful carbon dioxide.
And they are declining sharply.
Worldwide phytoplankton levels are down 40 percent since the 1950s, according to a study published Wednesday in the journal Nature. The likely cause is global warming, which makes it hard for the plant plankton to get vital nutrients, researchers say.
The numbers are both staggering and disturbing, say the Canadian scientists who did the study and a top U.S. government scientist.
“It’s concerning because phytoplankton is the basic currency for everything going on in the ocean,” said Dalhousie University biology professor Boris Worm, a study co-author. “It’s almost like a recession … that has been going on for decades.”
Half a million datapoints dating to 1899 show that plant plankton levels in nearly all of the world’s oceans started to drop in the 1950s. The biggest changes are in the Arctic, southern and equatorial Atlantic and equatorial Pacific oceans. Only the Indian Ocean is not showing a decline. The study’s authors said it’s too early to say that plant plankton is on the verge of vanishing.
Virginia Burkett, the chief climate change scientist for U.S. Geological Survey, said the plankton numbers are worrisome and show problems that can’t be seen just by watching bigger more charismatic species like dolphins or whales.
“These tiny species are indicating that large-scale changes in the ocean are affecting the primary productivity of the planet,” said Burkett, who wasn’t involved in the study.
When plant plankton plummet – like they do during El Nino climate cycles_ sea birds and marine mammals starve and die in huge numbers, experts said.
“Phytoplankton ultimately affects all of us in our daily lives,” said lead author Daniel Boyce, also of Dalhousie University in Halifax, Nova Scotia. “Much of the oxygen in our atmosphere today was produced by phytoplankton or phytoplankton precursors over the past 2 billion years.”
Plant plankton – some of it visible, some microscopic – help keep Earth cool. They take carbon dioxide – the key greenhouse gas – out of the air to keep the world from getting even warmer, Boyce said.
Worm said when the surface of the ocean gets warmer, the warm water at the top doesn’t mix as easily with the cooler water below. That makes it tougher for the plant plankton which are light and often live near the ocean surface to get nutrients in deeper, cooler water. It also matches other global warming trends, with the biggest effects at the poles and around the equator.
Previous plankton research has mostly relied on satellite data that only goes back to 1978. But Worm and colleagues used a low-tech technology – disks devised by Vatican scientist Pietro Angelo Secchi, in the 19th century. These disks measure the murkiness of the ocean. The murkier the waters, the more plankton.
It’s a proxy the scientific community has long accepted as legitimate, said Paul Falkowski of Rutgers University, who has used Secchi disk data for his work.
He and other independent scientists said the methods and conclusions of the new study made sense.
One of the world’s richest fisheries is off the coast of Peru. In most years winds from the southeast push warm surface water away from the coast. In its place, upwelling brings to the surface cold water rich in nutrients. These provide nourishment for the microscopic plants know as plankton .
Plankton normally provide food for a vast community of anchovies and other fish.The fish in turn supply food for seabirds. Not only is the fish catch economically important, but the harvesting of bird excrement (guano) provides a supply of valuable fertilizer.
Every few years the pattern of air circulation of the equatorial Pacific changes in a way that affects oceanic upwelling. This weather condition is known as El Niño. During El Nino, upwelling brings up warm water with few nutrients. A serious economic consequences of El Niño is its devastating effect on the Peruvian anchoveta fisheries. Populations of fish and seabirds vanish and anchovy catches dwindle during El Niño. (See our El Niño page.)
Some biologists fear that the over fishing of the anchoveta by humans, plus the eating of anchovies by large fish and seabirds, combined with the injurious effects of an intense El Niño episode, like the one in 1997-98, could reduce the anchoveta stock to such critically low numbers that recovery could be difficult. The 1972-73 El Niño caused a serious drop in the fish catch which took years to recover. Since then, the Peruvian government has worked hard to regulate fishing in their territorial waters. Fortunately they have been succesfull, and the fishery has recovered from even severe El Niños like the one in 1988-1989.