Navigation Links
Mice brains shrink during winter, impairing some learning and memory

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 t hat 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.


Source:Ohio State University

Related biology news :

1. Birds brains reveal source of songs
2. Supercomputers to focus brains on AIDS dilemma
3. Divergent life history shapes gene expression in brains of salmon
4. Jumping genes contribute to the uniqueness of individual brains
5. Experts discuss use of human stem cells in ape and monkey brains
6. Sharp older brains are not the same as younger brains
7. Animal brains hard-wired to recognize predators foot movements, Queens study suggests
8. Bird brains shrink from exposure to contaminants
9. Carnegie Mellon researchers discover key deficiencies in brains of people with autism
10. Gene therapy injected into the brains of mice with Huntingtons disease
11. Scientists identify 36 genes, 100 neuropeptides in honey bee brains
Post Your Comments:

(Date:11/19/2015)... MOUNTAIN VIEW, Calif. , Nov. 19, 2015 /PRNewswire/ ... authentication market, Frost & Sullivan recognizes BIO-key with the ... Strategy Leadership. Each year, Frost & Sullivan presents this ... comprehensive product line catering to the needs of the ... which the product line meets and expands on customer ...
(Date:11/17/2015)... 2015 Paris from 17 ... Paris from 17 th until 19 ... innovation leader, has invented the first combined scanner in the ... same scanning surface. Until now two different scanners were required: one ... capture both on the same surface. This innovation is ...
(Date:11/16/2015)... Nov 16, 2015  Synaptics Inc. (NASDAQ: ... solutions, today announced expansion of its TDDI product ... touch controller and display driver integration (TDDI) solutions ... These new TDDI products add to the previously-announced ... TD4302 (WQHD resolution), and TD4322 (FHD resolution) solutions. ...
Breaking Biology News(10 mins):
(Date:11/23/2015)... Calif., Nov. 23, 2015   Ceres, Inc . ... today financial results for the fiscal year ended August ... --> --> During ... forage and feed products with a better balance of ... signed distribution agreements with several leading crop input providers ...
(Date:11/23/2015)... ... November 23, 2015 , ... Shimadzu ... of its Nexera UC Unified Chromatography system. The award from R&D magazine recognizes ... products of the year in the analytical and testing category. R&D Magazine chose ...
(Date:11/23/2015)... 2015 The royalty-free a ... to develop daclatasvir for 112 low- and m ... --> --> The Medicines Patent Pool ... medicine, signing an agreement with Bristol-Myers Squibb for daclatasvir, a ... genotypes of the HCV virus.  The royalty-free licence will enable ...
(Date:11/23/2015)... 23, 2015 biochar market ... 2015, and it is expected to grow with a ... driving the growth of the global market include improved ... of biochar, increased government initiatives and stringent environmental regulations, ... stringent environment regulations are the key drivers for the ...
Breaking Biology Technology: