The role of the avian hippocampus in spatial memory

Avian hippocampal function is surveyed, using data drawn from three areas: conventional laboratory paradigms, pigeon navigation, and food-storing. Damage to the avian hippocampus disrupts performance in laboratory tasks that tap spatial learning and memory, and also disrupts both pigeon homing and cache recovery by food-storing birds. Further evidence of hippocampal involvement in food-storing is provided by the fact that the hippocampus of food-storing birds is selectively enlarged. These findings lend support to the notion that the hippocampus plays a critical role in spatial learning and memory. However, avian hippocampal lesions (like mammalian hippocampal lesions) also disrupt certain laboratory tasks that do not have an overt spatial component. Moreover, analysis of the effects of hippocampal lesions on navigation find, first, that basic navigational processes are left intact, and second, that at least some of the disruption of homing may be caused by disruption of the associability of information derived from the sun compass a non-spatial deficit. Finally, attempts to demonstrate that the enlarged hippocampus of food-storing birds is associated with enhanced spatial memory have failed to deliver conclusive support. The extensive parallels between effects of hippocampal lesions in birds and mammals suggest that both the spatial and the non-spatial deficits form part of a single syndrome, one that cannot readily be explained in terms of disruption of specifically spatial processes.