<P> In birds, the correspondence is sufficiently well established that most anatomists refer to the medial pallial zone as the "avian hippocampus". Numerous species of birds have strong spatial skills, in particular those that cache food . There is evidence that food - caching birds have a larger hippocampus than other types of birds and that damage to the hippocampus causes impairments in spatial memory . </P> <P> The story for fish is more complex . In teleost fish (which make up the great majority of existing species), the forebrain is distorted in comparison to other types of vertebrates: Most neuroanatomists believe that the teleost forebrain is in essence everted, like a sock turned inside - out, so that structures that lie in the interior, next to the ventricles, for most vertebrates, are found on the outside in teleost fish, and vice versa . One of the consequences of this is that the medial pallium ("hippocampal" zone) of a typical vertebrate is thought to correspond to the lateral pallium of a typical fish . Several types of fish (particularly goldfish) have been shown experimentally to have strong spatial memory abilities, even forming "cognitive maps" of the areas they inhabit . There is evidence that damage to the lateral pallium impairs spatial memory . </P> <P> It is not yet known whether the medial pallium plays a similar role in even more primitive vertebrates, such as sharks and rays, or even lampreys and hagfish . Some types of insects, and molluscs such as the octopus, also have strong spatial learning and navigation abilities, but these appear to work differently from the mammalian spatial system, so there is as yet no good reason to think that they have a common evolutionary origin; nor is there sufficient similarity in brain structure to enable anything resembling a "hippocampus" to be identified in these species . Some have proposed, however, that the insect's mushroom bodies may have a function similar to that of the hippocampus . </P> <Ul> <Li> <P> Hippocampus animation </P> </Li> <Li> <P> Pigeon hippocampus (HP) </P> </Li> <Li> <P> Morphology in four rodent species </P> </Li> <Li> <P> Main hippocampal regions in marmoset </P> </Li> <Li> <P> Cell number distribution across species </P> </Li> <Li> <P> Cell number to body weight ratios in rodent species </P> </Li> <Li> <P> Neuronal loss shown in rat CA1 following ischemia </P> </Li> </Ul>

Which brain structure is located at the very tip of the hippocampus