PMC

(a) During habituation, both groups quickly recognized and consumed the presented rewards. No differences between the treatments were detected. (b) During the training stage, both Empty and Homer1 OE animals learned to associate lever presses with the reception of a reward. Although Homer1 OE mice appear to show less motivational behavior, repeated measures ANOVA did not reveal a significant time × AAV interaction. (c) Fixed ratio/variable ratio results of training trial 10. No difference in lever press activity was evident between the experimental groups.

(a) Schematic of the injection site of the virus in the CA1 and the dentate gyrus (DG) of the dorsal hippocampus. The dotted square indicates the approximate area of visualization in Panel b. (b) Visualization of Homer1b/c expression in the hippocampal DG region 8 weeks after injection of control (Left panels) or Homer1b/c-expressing virus (Right panels) (Scale: 100 µm). (c) Homer1b/c mRNA levels in the hippocampus. Infection with the viral construct induced a robust increase in both CA1 and DG mRNA levels in the dorsal (dHC) and ventral (vHC) part of the hippocampus. Pictures show representative autoradiographs of Homer1b/c mRNA levels in the dorsal hippocampus of empty and Homer1 OE animals. * Significant from Empty virus, p<0.05.

(a) In 5 habituation trials, all wild type (WT) mice show growing interest in the presented reward. Most of the Homer1KO mice, however, do not consume the sucrose pellets. (b) The learning curve in the fixed ratio/variable ratio (FR/VR) stage is slightly, but not significantly higher in Homer1KO mice compared to WT animals. This is due to the above-average performance of a subset of Homer1KO mice that already showed a response to the reward in the habituation phase, while the greater part of the Homer1KO animals show a below-average performance, thereby largely increasing the variance of the sample. (c) FR/VR results of training trial 15. A strong bimodal distribution of the Homer1KO group becomes apparent, consequently resulting in no significant difference when compared to WT animals.