The role of CA3 and CA1 in the acquisition of an object-trace-place paired-associate task.

The hippocampus mediates associative learning involving spatial and temporal information. Specifically, paired associations in which a trace interval separates the elements appear to be associated within CA1. In contrast, CA3 appears to be involved in associations containing spatial elements. This suggests that CA3, but not CA1, is involved as long as the spatial association does not contain temporal elements; conversely, CA1 is involved when a temporal element is included, regardless of whether there are spatial elements present. In the present study, rats were run on an object-trace-place paired-associate learning paradigm. Rats with CA3 as well as rats with CA1 lesions showed deficits in the acquisition of this task. These results suggest that CA1 is involved in making arbitrary associations involving a temporal (trace) element, whereas CA3 is involved in making associations that involve spatial elements; furthermore, CA1 and CA3 interact in the presence of both spatial and temporal information.