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We established a test system (finger maze test) for evaluating learning and memory ability in infant cynomolgus monkeys. The system using a puzzle as enrichment is an experimental method that evaluates learning and long-term memory in a relatively short time (5-week training phase, 2-day learning test, and 2-day memory test which is conducted 2 months after the learning test). In this study, we investigated…

1) Long-term memory retention capacity
2) Spatial cognitive ability
3) Sex and age differences to expand the scope of finger maze test for pre-clinical learning and memorization researches

In Exp. 1, a memory test was conducted 2 and 4 months after the learning test to assess long-term memory retention capacity in 1-year-old infants. The success rate at the 2nd memory test (93.6%, 4 months after learning test) was comparable to the learning test and 1st memory test (2 months after the learning test), suggesting the infants could memorize what they had learned 4 months ago and long-term memory of over 4 months was assessable.

In Exp. 2, an inverted version of the maze was used to examine if they had simply memorized the correct pattern or were using spatial cognitive ability to recognize the structure of the apparatus. Two months after the learning test, a 2-day memory test with the previously learned task (positive task) was conducted, and a memory test opposite to the previous learned (opposite task) was then conducted for 4 days. The time taken for the test was longer in the opposite task than the positive task (194 vs 274 sec) on Day 1 but the success rate was comparable (86.4% vs 80.0%). The duration for each test decreased over 4 days (274 to 101 sec) and the high success rate continued on Days 2-4 (92.1% to 95.0%). These results indicated that animals recognized the 3D structure of the maze and had the ability to carry out new tasks based on learned memories.

In Exp. 3, the finger maze test was given to male and female monkeys of various ages (< 1 year, < 3 years, > 5 years) to examine age and sex differences. Although all generations completed the learning and memory task without sex differences, young adults (< 3 years) performed best and had the shortest training period.

These results show that the finger maze test is useful for assessing short- and long-term memory in cynomolgus monkeys, since they have advanced spatial cognitive ability. The test could be applied to pre-clinical learning and memorization assessment.

Inoue, H. Torihara, S. Kawabata,

A. Arima, H. Tsusaki

Shin Nippon Biomedical Laboratories, Ltd.