An Ontogenetic Study of Electrical Activities in the Cerebral Cortex of the Albino Rat

The cortical potentials (EEG) of the albino rat were studied from birth to maturity. For several days after birth the EEG recordings were mostly flat with occasional appearance of 6 to 12 c/s waves of low voltage. After 5 days a long sequence of highly rhythmic waves of the same frequencies was most characteristic, often synchronous with the respiratory cycle and even after gross bodily movement. Frequency of these rhythms increased to 14 to 18 c/s at 14 days. High-voltage slow waves during behavioral sleep appeared after 7 days from birth and sleep spindles were shown after 20 days. The “activated sleep” pattern was identified and the typical features of the adult EEG were nearly complete from 20 to 30 days of age.