The development of superficial infraslow potential oscillations of the brain in chick embryos

The development of superficial infraslow potential oscillations (ISPO) of brain hemispheres, cerebellum and optic lobes was studied in chick embryos between day 9 and 21 of incubation. The ISPO were firstly registered in brain hemispheres at day 10 of incubation, i.e. 5 days before the onset of spontaneous EEG activity. The ISPO in 10-day-old embryos had an average frequency of 9.9 c/min and an amplitude of 0.14 mV. During further development till hatching the frequency decreased to 7.5 c/min and the amplitude increased to 1.39 mV. Similar ISPO with the same developmental trend were also registered from the surface of the cerebellum and optic lobes. Superficial ISPO were not synchronized either between both hemispheres or between different fields of the same hemisphere.