The Use of Olfaction by Neonatal Mice for Navigation During the Blind Stage of Development Nicholas Corbin Hilker Department of Biological Sciences, York College of Pennsylvania Introduction:  A preference for home nesting material has been observed in the early development of many rodent species.  Pup mice are born without functional eyes and rely mostly on olfaction for sensory signals for the first 14 days after birth  Locomotion in neonatal mouse pups is observed around 9 days after birth while still in their blind stage of development  The odors of the mother and other siblings act as a scent source for pups, but their use on traveling long distances back to the nest is unknown Methods: Mice pups aged days were each tested in three out of four experiments. Pups were then tested again with eyes open (14-15 days) Test 1. Environmental bedding was fresh unscented bedding, nest bedding was old soiled bedding Test 2. Environmental bedding was old and soiled, nest bedding was fresh and unscented Test 3 Control. Environmental bedding and nest were old and soiled. This was done as a control test Test 4. Control conditions are used but a strip of environmental bedding was removed and replaced with fresh bedding Questions: The aim of this experiment is to test olfaction use by pups returning to their home nest. This lead to two research questions.  Is scent an important part of a pup’s ability to traverse an open area under different conditions?  Does the addition of sight affect how the pups traverse the environment? Results: Table 1. Mean weight of pups on test days______ __ Eyes ClosedEyes Open Tank g4.23 g Tank g4.48 g Tank g6.30 g Conclusion:  Nest finding at days seems to be highly reliant on olfaction.  Control test differed significantly from tests 2 and 4 showing that replacing of the nest, or a strip from the environment affect navigation due to olfaction.  Faster nest finding at days may be a combination of vision & olfaction as well as increased strength. Literature Cited: Schoenfeld, T A., and Corwin, J V. Maturation of Olfactory Exploration in Golden Hamsters. Developmental Psychobiology 1985; 18: Szerzenie, V, Hsiao, S. Development of Locomotion toward Home Nest Material in Neonatal Rats. Developmental Psychobiology 1976; 10: Wiedenmayer, C P, Myers, M M, Mayford, M, and Barr, G A. Olfactory Based Spatial Learning in the Neonatal Nice and its Dependence on CaMKII. Learning and Memory 2000; 2: Acknowledgment: I would like to thank Dr. Rehnberg for his support in the development and testing and presentation processes. I would also like to thank the Biology staff for their help and interest in this thesis experiment. Table 2. Analysis of speed data comparing eyes closed and open tests.____ Mean StDev a N b Min-Max Test 1 Eyes Closed – 1.17 Eyes Open – 3.22 Test 2 Eyes Closed – 0.71 Eyes Open – 4.22 Control Eyes Closed – 2.15 Eyes Open – 4.83 Test 4 Eyes Closed – 1.22 Eyes Open – 7.18 a. Standard Deviation b. Number of individuals tested