Effects of lesions of hippocampal fields CA1 and CA3 on acquisition of inhibitory avoidance

Performance decrements of inhibitory avoidance (IA) induced by lesions in either the dorsal or ventral hippocampus have been interpreted as a deficiency in acquisition. Alternative interpretations are that short-term learning occurs despite the lesions and the long-term performance decrements reflect a failure of consolidation or retrieval. To assess the alternative explanations of the performance decrements, rats received lesions in either CA1 or CA3 fields of dorsal and ventral hippocampus, respectively, 8 days before IA training. Retention was tested at 30 min or 24 h after training. Kainic acid lesions were also produced in either hippocampal field 1 day after training and retention measured 8 days later. The group assessed 30 min after IA training showed little or no performance decrements, whereas the remaining groups did show marked performance decrements. These results do not support the conclusion that the hippocampus is essential for acquisition and support the idea that the hippocampus is highly involved in the consolidation or retrieval of information germane to these procedures.