ABC news recently featured a story on staying healthy at work. Taking attention away from work even for a short time relieves mental fatigue.  A 2008 study that found that people improved their working memory span after viewing pictures from nature.     Attached is a link to the report:
. http://abcnews.go.com/Health/ways-stay-healthy-work/story?id=14363408#1

If you'd like to read Dr. Berman's complete study, here is the link.
http://www.umich.edu/~jlabpsyc/pdf/2008_2.pdf