Experiment #153 by Scott Brady is manifested for shuttle flight STS-107. this evaluation of space flight induced stress and its effects on neuronal plasticity will use 18 six month old C57B1/6 male mice. A 21 day evaluation study was proposed to determine the length of time gruops of 6, 9, or 12 mice could be housed in the Animal Enclosure Module (AEM) without odor breakthrough. This study was performed at NASA-Ames Research Center begining on September 15, 1999. NASA personnel, under teh direction of Project Scientist, Marilyn Vasques, were responsible for animal care, maintenance, facilities, hardware, etc. San Jose State personnel, under the direction of Professor Dan Holley, performed the odor panel evaluations and data reduction. We used similar procedures and methods for earlier tests evaluating female mice.