Seasonal change in the avian hippocampus

- The hippocampus undergoes seasonal change in a variety of birds.
- Seasonal changes include change in hippocampal size and hippocampal neurogenesis.
- Seasonal change is variable from year to year and not under photoperiodic control.
- Behaviour may be an important cause of seasonal hippocampal plasticity in birds.
- Neuroendocrine control of hippocampal neuroplasticity has been relatively little studied in birds.

The hippocampus plays an important role in cognitive processes, including memory and spatial orientation, in birds. The hippocampus undergoes seasonal change in food-storing birds and brood parasites, there are changes in the hippocampus during breeding, and further changes occur in some species in association with migration. In food-storing birds, seasonal change in the hippocampus occurs in fall and winter when the cognitively demanding behaviour of caching and retrieving food occurs. The timing of annual change in the hippocampus of food-storing birds is quite variable, however, and appears not to be under photoperiod control. A variety of factors, including cognitive performance, exercise, and stress may all influence seasonal change in the avian hippocampus. The causal processes underlying seasonal change in the avian hippocampus have not been extensively examined and the more fully described hormonal influences on the mammalian hippocampus may provide hypotheses for investigating the control of hippocampal seasonality in birds.