The polluted air contained fine particulate matter, the kind of pollution created by cars, factories and natural dust. The fine particulates are tiny about 2.5 micrometers in diameter, or about 1/30th of the average width of a human hair. These particles can reach deep areas of the lungs and other organs of the body.
The concentration of particulate matter that the mice were exposed to was equivalent to what people may be exposed to in some polluted urban areas, according to the researchers.
After 10 months of exposure to the polluted or filtered air, the researchers performed a variety of behavioral tests on the animals.
In a learning and memory test, mice were placed in the middle of a brightly lit arena and given two minutes to find an escape hole leading to a dark box where they feel more comfortable. They were given five days of training to locate the escape hole, but the mice who breathed the polluted air took longer to learn where the escape hole was located. The mice exposed to polluted air also were less likely to remember where the escape hole was when tested later.
In another experiment, mice exposed to the polluted air showed more depressive-like behaviors than did the mice that breathed the filtered air. The polluted-air mice showed signs of higher levels of anxiety-like behaviors in one test, but not in another.
But how does air pollution lead to these changes in learning, memory and mood? The researchers did tests on the hippocampal area of the mice brains to find the answers.
"We wanted to look carefully at the hippocampus because it is associated with learning, memory and depression," said Fonken, who, along with Nelson, are also members of Ohio State's Institute for Behavioral Medicine Research.
Results showed clear physical differences in the hippocampi of the mice who were exposed to polluted air compared to those who weren't.
The researchers looked specifically at branch
|Contact: Laura Fonken|
Ohio State University