Interactions of corticosterone and embryonic light deprivation on memory retention in day-old chicks.

Corticosterone, injected embryonically into eggs hatched in the dark, improved retention for a weak passive avoidance task in day-old chicks, the optimal time points for injection were days E19 to E20, resembling those found previously for light exposure, suggesting possible interactions between light and corticosterone during late embryonic development with consequent effects on post-hatch behaviour.