**6. Conclusion**

We discussed hippocampal function in a nonspatial stimulus discrimination task with a focus on the configural association theory and conflict resolution model. These functions were strongly supported by the observations that hippocampal theta power decreased during the presentation of a compound stimulus in a negative patterning task [32, 38]. A transient decrease in hippocampal theta activity was also observed during the presentation of a compound stimulus in the simultaneous feature-negative task but not in the compound stimulus discrimination task [32]. These results suggest that the decrease in hippocampal theta activity was elicited by behavioral inhibition of a conflict stimulus with overlapping elements. Therefore, we conclude that the hippocampus may play a role in this cognitive process. This conclusion strongly supports the conflict resolution model, in which the hippocampus plays a role in negative information processing for conflict stimuli in the nonspatial discrimination task. Moreover, data suggest a link between a decreased in theta power and decreased septal cholinergic activity and increased septal GABAergic activity. Finally, we conclude that the hippocampal neural activity derived from septal cholinergic and GABAergic activities plays a central role in behavioral inhibition for conflict stimuli with overlapping elements.
