Measuring Behavior 2005: Drott and Haun

A new behavior test for distinguishing spatial learning deficits from complex learning deficits in aged-rodents

J. Drott and F. Haun

NeuroDetective Int., Quakertown, PA, USA

The study reported here is an initial attempt to describe age-related differences in performance of foraging/hoarding behavior by pigmented rats. The traditional Barnes task, which assays spatial memory deficits in rodents, was modified to reveal a separate learning de.cit in aged rats, in addition to the memory deficit. The modification exploits a naturally occurring, complex behavior in rats, foraging for food.

Both 9 months and 33-36 months Fischer/Norway rats were allowed to forage for large food pellets placed in 3 of 15 possible food cups in the center of a circular table, and return with them to one of 8 boxes on the periphery. Location of the three pellets remained constant throughout testing, however the animal’s home box periodically changed location. All boxes were visible to the animal and were identical except for panels hidden behind felt that blocked entry to the 7 non-home boxes.

Using imagery analysis software, changes in foraging strategy as well as accuracy in returning to the home cage were measured over multiple trials. Measures taken included number of visits to all food cups, repeat visits to individual food cups during a foraging session before successfully finding a food pellet, and length of the return path to the animal’s home location following acquisition of a food pellet. The old animals’ foraging strategy was less efficient (more empty cups explored) compared to young animals, but both groups learned the home location equally well. When the home location was moved, the old animals were initially less accurate in returning to the new location, but improved their accuracy over several trials. However, foraging strategy in the aged animals never improved throughout the test. Thus this foraging/homing test provides an opportunity to detect drug effects on two very different cognitive deficits in old rats, one involving memory for a home location and the other involving complex learning.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.