Electro-ontogenesis of cerebral and cardiac activities in the chick embryo

Abstract

Spontaneous and metrazol-enhanced EEG activity was serially investigated in 55 chick embryos of 4 to 21 days incubation age. EKG was also recorded in 43 of these, either separately or simultaneously in 21. Occasional slow EEG waves, with intermittent silent intervals, were first recorded at the 4th day of incubation. These slow waves gradually became more regular and increased in amplitude as the days went by. By the 13th day fairly well marked low voltage fast activity appeared and became predominant in the later periods of incubation. On topical application of metrazol there was a potentiation of the cerebral activity, but no spikes appeared, and similar potentiation was occassionally produced by topical application of glucose, insulin and saline. Marked variations in rate, rhythm and regularity of the cardiac activity, with variable quiescent periods in between in younger ages, were recorded in different chick embryos. The EEG activity, however, did not show any variations between the rhythmically active or quiescent periods of the heart.