A longitudinal study of bioelectric activity in the pre- and post-hatch chick.

A technique for embryonic implantation and the subsequent recording of electrocortical, neck muscle, and ocular activity continously from the 20th day of incubation through hatching and the first few days thereafter is demonstrated. The embryonic maturation of the EEG, with a characteristic muscle burst pattern heralding hatching was found, supporting previous reports obtained with acute preparations. The technique for injection into the chorioallantoic membrane (CAM) vessels or direct deposition onto the CAM is also described. The usefulness of the embryonic neurophysiological implantation coupled with the injection at specific stages of development is discusses as an approach to the understanding of the parameters of the maturation of the sleep-wakefulness cycle, neurochemistry, and behavior.