SPATIAL MEMORY DEFICITS IN SEGMENTAL TRISOMIC TS65DN MICE

Spatial memory was assessed in the segmental trisomic 16 mouse (Ts65Dn ), a potential model for Down syndrome (DS), using the 12-arm radial m aze (RAM). Ts65Dn mice have a portion of mouse chromosome 16 syntenic to the distal end of human chromosome 21 triplicated. On each of 8 dai ly trials of the RAM, Ts65Dn mice made fewer correct choices than cont rol mice and performed at or near chance levels, indicating a deficit in spatial working memory. On trials 9 and 10, Ts65Dn mice performed a s well as control mice on the initial 12 choices, but required a great er number of choices to complete the RAM. The improved performance of Ts65Dn mice on trials 9 and 10 was lost when the animals were retested after a 50-day retention period, suggesting that long-term memory is also defective. These results are not likely explained by differences in either response bias or perceptual discrimination. Ts65Dn and contr ol mice displayed comparable levels of performance in spontaneous alte rnation in a T-maze, demonstrating that simple spatial memory was not impaired. In the elevated plus maze, Ts65Dn mice did not display highe r anxiety levels which could affect their performance in the RAM. In f act, Ts65Dn mice visited open arms on the elevated plus maze more freq uently and spent more time on open arms than did control mice. Taken t ogether, these results provide evidence for short- and long-term spati al memory deficits in Ts65Dn mice.