Electroencephalogram of the chicken recorded from the skull under various conditions

Electroencephalographic studies were carried out on chickens to determine the normal electroencephalogram (EEC) patterns from wakefulness to sleep and the effect of anesthesia. Sixteen electrodes were fixed to the frontal and parietal bones. EEC was recorded under unstressed condition. In the excited state, fast waves of 30 to 60 cps and of low amplitude were predominant. In the resting period, these waves shifted to slower ones of 14 to 24 cps, the amplitude remaining low as in the excited state. As the bird fell asleep, three main stages could be distinguished according to the correlation between the EEC patterns and behavioral states. Under ether anesthesia, four stages could be distinguished according to the EEC patterns and the responsiveness to afferent stimuli. By increasing the dose of nembutal, the correlation between the EEC pattern and the depth of anesthesia was studied. The “spindle burst”, or “barbiturate burst,” and the “fast wave” shown in mammals by the injection of barbiturates were not observed in the chicken.