Exp Neurobiol 2009; 18(2): 67-75
Published online December 31, 2009
© The Korean Society for Brain and Neural Sciences
Nuribalhae Lee, Jaehyun Im, Junehee Son and Bong-Kiun Kaang*
National Creative Research Initiative Center for Memory, Department of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul 151-747, Korea
Correspondence to: *To whom correspondence should be addressed.
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Freezing behavior is a widely used parameter that represents the level of fear. A number of studies on emotional learning have used this behavior for quantification of fear that results from a cue or a context. Even though the expression of freezing behavior is based on the dynamic interaction of mice with the environment, the effect of environmental stimuli on freezing behavior has not been studied extensively because of its minority compared to the effect of conditioning-stimuli. In this study, we found that the auditory environment of a context affects the freezing behavior of a mouse in it. This effect was not observed when the mouse was exposed to the context for the first time. However, during the second exposure, the level of freezing behavior increased significantly in an intensity-dependent manner, while the type, pitch, and rhythm of additional sounds involved in the context did not induce notable effects. This intensity-dependent effect was unrelated to the level of fear and anxiety, reflecting another aspect of the freezing behavior as a parameter for recognizing the pattern of normal behaviors.
Keywords: type of sound, pitch of sound, intensity of sound, rhythm of sound, freezing behavior, auditory environment