Lesions of the caudal area of rabbit medial prefrontal cortex impair trace eyeblink conditioning

The dorsolateral prefrontal cortex of the primate is an area known to be important for memory. Since the discovery of a homologous area in subprimate mammals, the caudal medial prefrontal cortex, rabbits have become useful in the investigation of working memory. The subprimate prefrontal cortex is intimately interconnected with the hippocampus, which is also recognized for its role in learning and memory. In addition, the hippocampus and prefrontal cortex have been shown to be similarly involved in a variety of tasks. Therefore, we hypothesized that the caudal medial prefrontal cortex of the rabbit would be necessary for acquisition of the hippocampally dependent trace eyeblink conditioning task. A total of 16 young rabbits (Oryctolagus cuniculus) received bilateral aspiration lesions of the prefrontal cortex. Six of the lesioned subjects were unable to acquire the trace eyeblink conditioning task, but were unimpaired when tested subsequently in the hippocampally independent delay conditioning task. The lesions of these 6 subjects either were limited to or extended into the caudal medial prefrontal cortex. In the remaining 10 subjects, which were not impaired in trace conditioning, the lesions were limited to the rostral pole. Our results support our original hypothesis and provide further evidence of the involvement of the subprimate caudal medial prefrontal cortex in learning.