Development of electrical activity in cerebral hemispheres of the chick embryo.

Abstract

Summary and Conclusions1. A study of the beginning and development of the EEG in 73 chick embryos is made. 2. “Spontaneous” electrical activity and that produced by strychnine appear simultaneously on the 13th day. 3. “Spontaneous” activity undergoes changes during the course of embryonic development. The “early” rhythm appearing on the 13 th day gradually increases in frequency and voltage and becomes more constant. On the 16th day the high voltage “late” rhythm appears, becoming more constant on subsequent days. 4. Strychnine causes the appearance of spikes, which are generally biphasic, and increases the amplitude, frequency and constancy of the “spontaneous” activity in most experiments. 5. With development of the embryo, the strychnine spikes become of shorter duration and higher voltage, pointing to a better synchronization of the neurones. Frequency increases and spikes begin to appear earlier as the embryo grows. 6. From the 14th day spike discharges are to be seen in the embryonic brain, similar ...