Impaired prepulse inhibition (A and B) and latent
inhibition (C–F) of CN mutant mice. Startle amplitude
was not different between genotypes (A), but the percentage prepulse
inhibition was significantly smaller in CN mutants compared with controls
(B). Percent freezing during the conditioning phase was significantly
less in CN mutants (D) compared with controls (C), most
likely due to their hyperactivity. CN mutants traveled longer distances in
response to shocks than controls (Insets in D and
C, respectively). Freezing during contextual testing was not
significantly different between genotypes (C and D). In cued
testing, the percent freezing for the P group was significantly lower than
that of the NP group in control mice, indicating significant latent inhibition
in control mice (E). In contrast, the CN mutants failed to show a
significant latent inhibition (F).