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 How circadian clocks communicate with each other
30.05.2017 | Julius-Maximilians-Universität Würzburg

nachricht Reptile vocalization is surprisingly flexible
30.05.2017 | Max-Planck-Institut für Ornithologie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Strathclyde-led research develops world's highest gain high-power laser amplifier

The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.

The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

Reptile vocalization is surprisingly flexible

30.05.2017 | Life Sciences

EU research project DEMETER strives for innovation in enzyme production technology

30.05.2017 | Power and Electrical Engineering

New insights into the ancestors of all complex life

29.05.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>