Correlation between delta and spindle components in compressed spectral array during nocturnal sleep in mentally...

The correlation between the delta and spindle components in compressed spectral array in 96 mentally retarded children (from 3 months to 12 years of age) was studied throughout nocturnal sleep. In 57 (59.4%, group A) of 96 subjects, periodic changes of delta and spindle rhythm powers were noted in sleep EEG. In 29 subjects (30.2% group B), delta but not spindle rhythm powers were found, and in the remaining 10 subjects (10.4%, group C) neither delta nor spindle rhythm powers were found throughout nocturnal sleep. A significant increase in abnormal clinical EEG was found in groups B and C as compared with group A. A significant decrease in the developmental quotient (DQ) was found in groups B and C as compared with group A. A significant decrease in DQ was also found in group C as compared with group B.