Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Evidence That Neurons Prune Only "Twigs" to Rewire Themselves

23.10.2003


By using a laser microscope to spy on individual nerve cells in living mice, researchers have discovered that neurons’ wiring remain largely stable, providing a solid scaffold to accommodate the challenges in their environment. Specifically, the scientists found that the neuronal branches called "dendrites" remain largely unchanged in the highly active olfactory processing region of the mouse brain. Such evidence suggest that dendrites in the adult brain form a stable background even in the face of ongoing changes that form part of everyday experience.


Lawrence C. Katz, PhD



Besides providing a better basic understanding of the dynamic processes of brain rewiring, the researchers believe their findings might yield insights into such disorders as epilepsy and Alzheimer’s disease, which are marked by aberrant neural circuitry.

Dendrites are the branches of neurons that support the multitude of interconnections by which one neuron triggers a nerve impulse in its neighbors in the intricate neural pathways of the brain.


The research was reported in the November 2003 issue of the journal Nature Neuroscience by Howard Hughes Medical Institute investigator Lawrence Katz, Ph.D., and colleague Adi Mizrahi, both at the Duke University Medical Center.

"The brain faces two challenges in maintaining its functionality in a changing environment," said Katz. "One is to remain stable enough so that the basic things we need to do to interpret the world remain consistent. And the other is to continually adapt to the changing environment, which places a high premium on the ability to alter neural circuitry."

The brain is known to undergo large-scale wiring during embryonic development after such drastic events as a stroke or loss of a limb. However, said Katz, a central question in neurobiology is whether such dendritic alterations take place during the formation of long-term memories.

To explore the nature of such rewiring, Mizrahi and Katz studied neurons in the neural structure called the olfactory bulb -- the collection of neurons that represent the initial processing stage for information from odor sensing receptors in the nose.

"The olfactory bulb is one of only two areas of the brain where new neurons are being generated throughout life," said Katz. "Neurons in the olfactory bulb are constantly losing synapses linked to sensory cells that are dying and gaining new ones connected to new sensory cells." Thus, he said, detailed observation of those neurons should yield a clear look at neurons in the process of rewiring during ordinary experience.

The scientists used a laser microscopy technique that enabled them to watch changes in specific neurons genetically tagged with a fluorescent protein, as the mice were presented with changes in their environment. The transgenic mice were developed by Duke neurobiologist Guoping Feng, Ph.D., and his colleagues.

"Importantly, this technique enabled us to look in real time at the changes in a single neuron in the same animal; not at populations of neurons and not at different animals," said Katz. "We could follow over time how dendrites responded to ongoing change." In initial studies, the researchers found only subtle changes in the neurons.

"The changes bordered on the imperceptible -- like a tree that lost or gained only a few twigs over time," said Katz. "It wasn’t what we initially thought, that the neurons would be like rose bushes in spring, in which a tremendous amount of dendritic structure would be gained." Even when the scientists placed the mice in an enriched "Disneyland" of structures and smells to explore, they saw few changes in dendritic structure. This, despite the fact that other researchers had found that manipulating the odor environment drastically increased turnover of neurons in the olfactory bulb. Nor did the scientists see significant changes when they taught the animals to seek out a particular odor to gain a reward.

The only way they could induce major changes, they found was to use the molecular "sledgehammer" of a drug known to make neurons hyperactive, "so we knew they had the capacity to undergo change," said Katz.

"We’ve concluded from these findings that the overall theme of this area of the brain is stability, and that these dendrites are not undergoing large-scale changes under natural conditions, even in response to changes in their environment," said Katz. "My own view is that there is a large backbone of stability in these areas and relatively low levels of plasticity, despite the fact that new neurons are being constantly generated," said Katz.

According to Katz ongoing studies are using the combination of laser microscopy and cell tagging to study plasticity in other regions of the brain, particularly the central site of learning, the hippocampus.

Such studies could yield significant insights into disorders that involve brain rewiring, he said. "Dendritic degeneration is a hallmark of Alzheimer’s disease, and dendritic changes are known to occur in epilepsy," said Katz. "So, understanding what is normal and what is pathological -- and the mechanisms that produce such changes -- could offer insights into these diseases." For example, he said, by crossing mouse strains that show epilepsy with the fluorescently tagged strain, it would be possible to study in detail alterations in dendritic wiring that might contribute to the disorder.

Dennis Meredith | dukemed news
Further information:
http://dukemednews.org/news/article.php?id=7129
http://www.neuro.duke.edu/Faculty/Katz.htm

More articles from Life Sciences:

nachricht Bare bones: Making bones transparent
27.04.2017 | California Institute of Technology

nachricht Link Discovered between Immune System, Brain Structure and Memory
26.04.2017 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Bare bones: Making bones transparent

27.04.2017 | Life Sciences

Study offers new theoretical approach to describing non-equilibrium phase transitions

27.04.2017 | Physics and Astronomy

From volcano's slope, NASA instrument looks sky high and to the future

27.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>