The effects of environmental exposure to DDT on the brain of a songbird: changes in structures associated with mating and song.

Dichlorodiphenyltrichloroethane (DDT) is a persistent organochlorine compound found worldwide that causes significant anatomical, physiological and behavioural abnormalities in humans and wildlife. However, little is known about whether environmental exposure to DDT affects the brain. Here, we show that environmental exposure to DDT alters the brains of American Robins (Turdus migratorius) in several ways. Increasing levels of DDT resulted in: (i) smaller brain and relative forebrain volumes; (ii) a reduction in the size of two song nuclei, nucleus robustus arcopallialis (RA) and HVC; and (iii) a drastic reduction in neuronal size and overall volume of nucleus intercollicularis (ICo), a structure that is critical for normal sexual behaviour. These changes likely result from stress, direct neurotoxicity and androgen receptor antagonism by the primary metabolite of DDT, p,p'-DDE and this is corroborated by analyses of brain region volumes and p,p'-DDE levels. Our results therefore demonstrate that environmental exposure to DDT is correlated with significant changes in the brain and specifically those structures related to mating and song. Given the magnitude of these changes in the brain and the fact that environmental DDT exposure was restricted to early development, we conclude that both humans and wildlife that live in DDT contaminated environments may be at risk of neurological damage.