Pattern discrimination is affected by entopallial but not by hippocampal lesions in zebra finches

We compared the effect of entopallial lesions with that of hippocampal lesions on pattern discrimination in zebra finches. The birds were trained to discriminate a feeder with a dot pattern from feeders with a stripe pattern, all located at the floor of a small aviary. When the birds had learned the discrimination, entopallium or hippocampus was damaged by ibotenic acid injection. Entopallial lesions caused deficits in the discrimination, while hippocampal lesions did not. As shown in previous experiments using the same experimental design with feeders of one colour and without distinct pattern [Watanabe S, Bischof HJ. Effects of hippocampal lesions on acquisition and retention of spatial learning in zebra finches. Behav Brain Res 2004;155:147–52], hippocampal lesions cause strong deficits in spatial orientation. Taken together, our experiments prove that the avian hippocampus is involved in spatial learning, but not in pattern discrimination tasks.