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					                         The Use of Olfaction by Neonatal Mice for Navigation During the
                                           Blind Stage of Development
                                                                                                        Nicholas Corbin Hilker
                                                                                                                                                                                                                         Distance Traveled With Eyes Open
                                                                 Department of Biological Sciences, York College of Pennsylvania
                                                                                                                                                                                                             500
Introduction:                                                                                                                                                                                                                                                   Test 1
                                                                                                                                                                                                                                                                Test 2
                                                                                                                                                                                                                                                                Control
                                                                                                                                                                                                                                                                Test 4
 A preference for home nesting material has been
observed in the early development of many rodent
                                                                                 Results:                                                                                                                    400



                                                                                              Mean Time of Travel by Pup Mice with Eyes Closed or Opened
species.




                                                                                                                                                                                             Distance (cm)
                                                                                                                                                                                                             300
                                                                                                       600                       b                                     Eyes Closed
                                                                                                                                                                       Eyes Opened

 Pup mice are born without functional eyes and rely                                                   500                                                         b




                                                                                  Time of Travel (s)
                                                                                                                                                                                                             200
mostly on olfaction for sensory signals for the first 14                                               400
                                                                                                                                                    a
days after birth                                                                                       300
                                                                                                                  a

                                                                                                                                        x                                                                    100
 Locomotion in neonatal mouse pups is observed                                                        200
                                                                                                                         xz                                               yz
around 9 days after birth while still in their blind stage of                                          100
                                                                                                                                                             y
                                                                                                                                                                                                               0
development                                                                                              0                                                                                                         0   100      200     300
                                                                                                                                                                                                                                      Time (s)
                                                                                                                                                                                                                                                   400          500         600




                                                                                                                                                       ol
                                                                                                                     1




                                                                                                                                    2




                                                                                                                                                                      4
                                                                                                                  st




                                                                                                                                 st




                                                                                                                                                                   st
                                                                                                                                                    tr
                                                                                                                                                 on
 The odors of the mother and other siblings act as a




                                                                                                                 Te




                                                                                                                               Te




                                                                                                                                                                  Te
                                                                                                                                                C
                                                                                                                                                                                             Figure 4. The distance of travel by pups and the time taken to find the home
                                                                                          Figure 1. The mean time of travel by pup mice in different test                                   nest with their eyes open. Pups were given10 min to find the nest in each test.
scent source for pups, but their use on traveling long                                    conditions, during eyes open and eyes closed stages of life. Bars that
                                                                                          share a letter are considered not significantly different. Data were
                                                                                                                                                                                              If the nest was not found after 10 min, a score of 600 seconds was given.

distances back to the nest is unknown                                                     statistically tested using a Kruskal-Wallis Test. Eyes closed and eyes
                                                                                          open were statistically tested separately                                                        Table 2. Analysis of speed data comparing eyes closed and open tests.____
                                                                                                                                                                                                                   Mean        StDeva        Nb       Min-Max
                                                                                                                                                                                           Test 1
                                                                                                                                                                                                                                                      0.26 – 1.17
Questions:                                                                                                                Distance Traveled with Eyes Closed
                                                                                                                                                                                           Eyes Closed
                                                                                                                                                                                           Eyes Open
                                                                                                                                                                                                                   0.82
                                                                                                                                                                                                                   1.78
                                                                                                                                                                                                                               0.246
                                                                                                                                                                                                                               0.671
                                                                                                                                                                                                                                             17
                                                                                                                                                                                                                                             17       0.86 – 3.22

                                                                                                                                                                                           Test 2
The aim of this experiment is to test olfaction use by pups                                            600
                                                                                                                                                                                           Eyes Closed                       0.38      0.188          16          0.02 – 0.71
                                                                                                                                                                               Test 1
returning to their home nest. This lead to two research                                                                                                                                    Eyes Open                         1.87      0.853          15          0.59 – 4.22
                                                                                                                                                                               Test 2
                                                                                                       500                                                                     Control
questions.                                                                                                                                                                     Test 4      Control
                                                                                                                                                                                           Eyes Closed                       0.95      0.53           33          0.07 – 2.15
                                                                                                                                                                                           Eyes Open                         2.71      0.968          32          1.33 – 4.83
                                                                                                       400
                                                                                  Distance (cm)




 Is scent an important part of a pup’s ability to traverse an                                                                                                                             Test 4
                                                                                                                                                                                           Eyes Closed                       0.51      0.273          29          0.02 – 1.22
open area under different conditions?                                                                  300
                                                                                                                                                                                           Eyes Open                         3.14      1.701          26          0.57 – 7.18
                                                                                                                                                                                           a. Standard Deviation
                                                                                                                                                                                           b. Number of individuals tested

                                                                                                       200
 Does the addition of sight affect how the pups traverse
the environment?                                                                                       100                                                                                 Conclusion:
                                                                                                                                                                                            Nest finding at days 10-13 seems to be highly reliant
                                                                                                         0
Methods:                                                                                                     0           100     200          300           400    500         600         on olfaction.
                                                                                                                                            Time (s)

                                                                                                       Figure 2. The distance of travel by mouse pups compared to the time taken to find
Mice pups aged 10-13 days were each tested in three out of four                                        the home nest with their eyes closed. Pups were given 10 min to find the nest in
                                                                                                                                                                                           Control test differed significantly from tests 2 and 4
                                                                                                       each test. If the nest was not found after 10 min, a score of 600 seconds was
experiments. Pups were then tested again with eyes open (14-15 days)                                   given.
                                                                                                                                                                                           showing that replacing of the nest, or a strip from the
Test 1.
                                                                                                                                                                                           environment affect navigation due to olfaction.
     Environmentalbedding was fresh unscented bedding, nest bedding
     was old soiled bedding
                                                                                                                                                                                            Faster nest finding at days 14-15 may be a
Test 2.
                                                                                                                                                                                           combination of vision & olfaction as well as increased
     Environmental bedding was old and soiled, nest bedding was fresh                                                                                                                      strength.
     and unscented
                                                                                                                                                                                           Literature Cited:
Test 3 Control.                                                                                                                                                                            Schoenfeld, T A., and Corwin, J V. Maturation of Olfactory Exploration in Golden Hamsters. Developmental
                                                                                                                                                                                           Psychobiology 1985; 18: 515-528.
     Environmental bedding and nest were old and soiled. This was done                                                                                                                     Szerzenie, V, Hsiao, S. Development of Locomotion toward Home Nest Material in Neonatal Rats. Developmental
     as a control test                                                                                                                                                                     Psychobiology 1976; 10: 315-321.

Test 4.                                                                                                                                                                                    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: 1051-1055.
                                                                                                        Table 1. Mean weight of pups on test days______                           __
     Control conditions are used but a strip of environmental bedding was
     removed and replaced with fresh bedding
                                                                                                                        Eyes Closed                  Eyes                      Open        Acknowledgment:
                                                                                                        Tank 4                5.45 g                                           4.23 g      I would like to thank Dr. Rehnberg for his support in the development and testing and presentation
                                                                                                        Tank 5                6.10 g                                           4.48 g      processes. I would also like to thank the Biology staff for their help and interest in this thesis
                                                                                                        Tank 6                6.21 g                                           6.30 g      experiment.

				
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