Age-related changes of the avian brain measured by FDG-PET Imaging

Abstract

Functional asymmetries of the brain’s hemispheres play an important role in the completion of cognitive tasks by human and non-human vertebrates. For pigeons, the left hemisphere is more important for discrimination of local cues, such as discriminating pieces of grain scattered among grit, whereas the right hemisphere is more important for processing global cues, such as a predatory bird flying overhead. Brain functionality declines with age, and the hemispheres age at different rates. We investigated the age-related differences in metabolic rate of each hemisphere by using PET imaging. Adult, old and very old pigeons searched for grains scattered among grit using both eyes, only the right eye or only the left eye. Overall, the activity of both hemispheres decreased significantly in old and very old subjects compared to the adult group, which resulted in significantly poorer performance by very old subjects when the left hemisphere was not available (using only the left eye). However, in spite of the reduction in the brain activity of the old subjects, they could still perform the task significantly better than the very old group. Also, Lateralization Index differed significantly among all there eye conditions only in adult pigeons. In conclusion, coupling behavioural study with a neuroimaging technique, we showed that the avian brain, similar to the mammalian brain, can compensate for the effects of aging to a limited extent and until a certain age.