Figure 7.

Type III Nrg1 heterozygous mice have impaired delayed alternation memory performance. A, B, Performance (percentage of correct trials) of 18 wild-type (+/+) and 22 heterozygous (+/−) animals in a continuous delayed alternation test using 15 s (A) or 60 s (B) as the delay time. Each point represents the average performance of 2 d testing from individual animals. The bold lines indicate the median (50th percentile). The dashed line indicates chance performance. There is a significant deterioration in performance of +/− animals with 60 s delay (Kolmogorov–Smirnov test, χ² = 11.1, p_genotype < 0.008), whereas there is no difference between the performance of +/+ and +/− mice with brief intertrial intervals (15 s delay: K–S test, χ² = 2.0, p_genotype = 0.72). **p < 0.01. C, Scatter plots of the change in performance at 15 versus 60 s delay times for each animal. Positive values reflect better performance at 60 s compared with that at 15 s; negative values reflect worse performance at 60 versus 15 s. In +/+ animals, increasing the intertrial interval to 60 s resulted in little change in performance (p_{delay time} > 0.8 for wild type). In contrast, the same intertrial interval shift in +/− animals resulted in decreased performance in 17 of the 22 +/− mice. Heterozygote animals had a significant decrease in performance with increased intertrial time (Kolmogorov–Smirnov test: χ² = 11.3; p_{delay time} < 0.003). **p < 0.01.