Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mice brains shrink during winter, impairing some learning and memory

13.05.2005


The brains of one species of mouse actually shrink during the winter, causing the mice to have more difficulty with some types of learning, a new study found.



The results showed that, during the short days of winter, white-footed mice had impaired spatial memory – the mental map that helps them remember important places in their environment. This is one of the first studies to show seasonal changes in the structure and the functioning of brains of mammals, said Randy Nelson, co-author of the study and professor of psychology and neuroscience at Ohio State University . The changes in the brain may help the mice conserve energy to survive during the cold winter season when food is scarce and conditions are harsh. “The brain uses a lot of energy relative to its weight,” Nelson said. “Like many mammals, mice need to reduce their energy costs during winter, and the brain is a good place to do that.”

And while there are obviously many differences between mice and humans, studies like this may one day help researchers gain insight into seasonal brain dysfunctions in humans such as seasonal affective disorder, Nelson said. Nelson conducted the study with Leah Pyter, a graduate student in neuroscience at Ohio State , and Brenda Reader, an undergraduate psychology major at Ohio State . The findings were published in the May 4 issue of the Journal of Neuroscience. In one set of experiments, the researchers used 20 adult male white-footed mice. Using artificial light, some mice were kept in short days – such as they would face in winter – with eight hours of light per day for 13 weeks before the beginning of the study. Other mice were kept in long days, simulating summer, with 16 hours of daylight for 13 weeks.


Their spatial learning and memory were tested using a water maze test in which the mice had to swim to find an escape platform hidden just below the surface of opaque water. They were tested for several days to determine how long it would take them to find the platform, and whether they remembered where the platform was from day to day. Results showed that mice that were kept in short days – simulating winter – took longer and swam farther before they found the hidden platform than did the long-day mice, indicating they had more trouble learning where the platform was. Moreover, they didn’t remember its location as well from one day to the next.

However, other tests showed that nonspatial learning and memory, including sensory abilities, were not affected by short days. “It appears that only specific kinds of brain function are impaired during winter,” Nelson said. In a second experiment, 16 adult male white-footed mice were kept in short or long days for 14 weeks, after which they were sacrificed. The researchers then examined differences in the brains between mice kept in the two differing conditions. These results showed that mice kept in short days had on average a smaller brain mass compared to the other mice, even when taking into account that their overall body mass was smaller, too.

In addition, the researchers found changes in a region of the brain – the hippocampus – that is involved in spatial memory. Mice in short days had a proportionally smaller hippocampus, as well as changes in spine density there that have been associated with spatially related memory and learning performance. “We predicted that when you reduce the size of the hippocampus, it would have an impact on learning, and that’s what we found,” Nelson said. The shrinking of the brain corresponds to a season when the mice may have less need for spatial memory, Nelson said. “They don’t maintain as large a territory in the winter,” he said. Nelson said he and his colleagues believe it may be the hormone melatonin which controls the changes in brain size and function in mammals such as these white-footed mice. Scientists know that levels of melatonin are associated with seasonal changes in daylight.

Melatonin is also found in humans, and that’s one reason why future research on how brain structure changes by season may be applicable to human conditions like seasonal affective disorder. The researchers are continuing work to look at the role of melatonin, and also to examine seasonal changes in brain structures in other types of mammals.

This study was supported by grants from the National Institutes of Health and the National Science Foundation.

: Randy Nelson | EurekAlert!
Further information:
http://www.osu.edu

More articles from Life Sciences:

nachricht Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY

nachricht NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Global study of world's beaches shows threat to protected areas

19.07.2018 | Earth Sciences

New creepy, crawly search and rescue robot developed at Ben-Gurion U

19.07.2018 | Power and Electrical Engineering

Metal too 'gummy' to cut? Draw on it with a Sharpie or glue stick, science says

19.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>