Fig. 5.
Mice derived from embryo culture exhibit impaired spatial memory. (A) Average percentage of time spent in each quadrant of the pool during probe trials on the first and twenty-first day (day 1 and day 21) after training. The platform was located in the target quadrant, and the percentage of time in this quadrant, as well as in the opposite, adjacent clockwise (CW), and adjacent counterclockwise (CCW) quadrants, is shown. Filled bars, in vivo-derived mice; open bars, KSOM-derived mice; hatched bars, WM-derived mice. (B) Relative percentage of time in the quadrant that contained the platform during retention (probe) trials. To measure the retention of spatial information on a per subject basis, an animal's performance on day 21 was compared with its performance on day 1, and the data are expressed as this ratio minus 1 so that identical performance on day 21 and day 1 results in a value of 0. The data here and in C are both calculated in this way and are expressed as the mean ± SEM. *, The differences between animals derived from cultured embryos are statistically different from animals derived from embryos that develop in vivo; P < 0.004 for relative time spent in target quadrant. The observation that the control mice spend more time in the quadrant after 21 days than after 1 day is a phenomenon called consolidation of memory (40). (C) Relative distance from the platform location during retention (probe) trials. *, The differences between animals derived from cultured embryos are statistically different from animals derived from embryos that develop in vivo; P < 0.03 for relative distance from platform position. The numbers of mice examined are described in the legend to Fig. 4, and the observed differences cannot be attributed to genotype (data not shown).