Role of interference in retention by rats with hippocampal lesions.

Involvement of the hippocampus in memory was studied in the rat by employing a retention task with and without interpolated activity. Rats with extensive damage to hippocampus were able to relearn a preoperatively acquired single-alternation task with savings and to perform the single alternation with relatively long delays at a level similar to that of control subjects. However, hippocampals were more affected than normals by an interpolated activity that interferes with retention. The finding of normal retention combined with increased susceptibility to interference supports the view that the memory impairment in subjects with damage to hippocampus may be due to an excess of interference among stored information.