Figure 10.

Anhedonic rats were impaired in the object-place paired-associate learning task. The object-place paired-associate learning task is a touchscreen task in which rats learn to associate objects (shapes) based on their specific locations on the touchscreen. Control rats had a gradual improvement in this task and showed a continuous increase in the maximum number of consecutive correct trials. The anhedonic rats were impaired in this task. They could not learn the task, because they could achieve fewer consecutive correct trials. The difference between the two groups was most prominent in the end of the testing period. The number of consecutive correct trials within one session is a combined readout of working memory, visual attention and executive functions. Impaired performance of the anhedonic rats indicates disturbed functioning of hippocampal-prefrontal-cortical neural circuits. Furthermore, we found significant correlation between the sucrose intake of the animals and their performance in this learning task. The x-axis displays the absolute session number. As it is shown on Figure 1, the animals were first trained in this learning task for 3 weeks and then, the testing period of 5 weeks started. During this testing period, every day each animal would perform one session which consisted of maximum 75 task trials or 45 min, whatever would be reached first. Data was log-transformed. Data was compared with repeated measurements mixed model analysis and simple main effects of group were tested for each session. *P < 0.05; **P < 0.01; ***P < 0.001 vs. the Control group in the same Session.