Effects of hippocampal lesions on repeated acquisition of spatial discrimination in pigeons

Anatomical studies of avian hippocampus suggest this structure is a counterpart of that of mammals, and allometric studies of food storing birds support the idea that the avian hippocampus has spatial cognitive functions. In the present study, the spatial cognitive function of hippocampus in pigeons was examined by lesion experiments. Pigeons were trained on either a spatial discrimination, or a spatial discrimination with an added color cue, using a repeated acquisition procedure. In the spatial task, the pigeons were trained to discriminate the position of three keys. Each time the subjects reached the criterion, they were trained on different discriminations in which one out of two previously incorrect keys became the correct key. In the task with color added, each key had its own color, so the subject had both spatial and color cues for the discrimination. The hippocampal lesions disturbed the acquisition of the spatial discrimination, but not in the task in which color cues were added. These results suggest that the avian hippocampus have a crucial role in acquisition of spatial discriminations.