MRI identification of dorsal hippocampus homologue in human brain.

We investigated hippocampal substructure in the rat, cat, dog, and human by means of magnetic resonance imaging to elucidate phylogenetic differences in longitudinal organization. Multidirectional high-resolution images obtained with a 3 T scanner revealed that the dorsal part of the hippocampus was well developed in the rat, cat, and dog brain, and was homologous to the hippocampal tail, a poorly-developed posterior part, in the human. We conclude that the dorsal hippocampus of laboratory animals corresponds to the hippocampal tail in the human brain, which is considered to be hypoplastic and of less importance clinically than more anterior regions. These data may help in understanding phylogenetic, and in correlating results from animal experiments with clinical findings on the functions and pathologies of the human hippocampus.