Latencies of jumps across the hurdle.

<p>Mean latencies of jumps across the hurdle of the shuttle-box after tone onset are plotted as a function of the training sessions. There are no systematic significant differences of latencies between the experimental groups of animals. At training session 15, R552H mutants are significantly different from WTs and S321X mutants (p<0.05; F = 4.42) and at training session 18, WTs differ from R552H mutants (p<0.05; F = 5.41). At any other training session, significant differences did not occur (F-values<2.50). Standard deviations are shown only for the WTs for better visibility. They are of the same order of magnitude for both groups of heterozygous mutants.</p

Logistic growth functions modeling the increase of the discrimination index d′ as function of the training day.

<p>d′ expresses the achieved average performance level of tone discrimination of the animals in each experimental group (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0033130#s3" target="_blank">Methods</a>). Discrimination performance of the WTs increases rapidly and stays at a maximum level already from day 2 onwards. Discrimination performance of the R552H heterozygotes increases slowly but finally reaches the level of the WTs. Discrimination performance of the S321X heterozygotes increases very slowly and does not reach the levels of WTs and R552H heterozygotes. The correlation coefficients of the growth functions are statistically significant (p<0.01 in each case).</p

Learning curves of wildtype (a), heterozygous R552H mutant (b), and heterozygous S321X mutant (c) mice.

<p>For all 20 training days (one training session per day) the mean numbers of jumps across the hurdle averaged from the performances of the 11 animals per experimental group are shown. The animals could show hits (CR+) in the presence of 12 kHz tones or false alarms (CR−) in the presence of 7 kHz tones. Since each training session consisted of 60 trials with 30 randomized presentations of both CS+ and CS− a maximum of 30 hits and 30 false alarms could be reached if the animals responded to each tone with a jump, irrespective of the tone frequency. The larger the distance is between the CR+ and CR− curves the better is the learning performance. Standard deviations of the means are shown only for one side to improve readability of the data. Statistically significant differences between the CR+ and CR− rates calculated for each training session are indicated as ** p<0.01; *** p<0.001.</p

Spontaneous motor behavior.

<p>Mean numbers of spontaneous jumps across the hurdle of the shuttle-box during the three minutes before the beginning of the daily training session. At the first training day, WTs show significantly more spontaneous jumping compared to both types of heterozygous mutants (*** p<0.001 in each case; F-value of the ANOVA = 14.92). At the second training day, the WTs show significantly more jumps than the heterozygous R552H mutants (p<0.02 **; F-value of the ANOVA = 5.12). For training days 3–13, 18 and 20 the ANOVA-tests did not lead to significant differences, F<3.42). WTs showed more spontaneous jumps compared to both mutants (p<0.05*; F>5.30) on days 17 and 19, and compared to R552H mutants (p<0.05*; F>4.40) on days 14–16. Standard deviations of the means are shown only for one side to improve readability of the data.</p