Analysis of the electroencephalogram in growing calves by use of power spectrum and cross correlation

Abstract

Objective - To determine postnatal maturation of findings in the electroencephalogram (EEG) of calves and estimate the degree of electrophysiologic activity, using power spectrum and cross-correlation analyses of the EEG. Animals - 10 clinically normal Japanese Black calves ranging in age from 1 to 10 weeks. Procedure - EEG were recorded at various stages of consciousness. Power spectrum and cross-correlation analyses were applied to a relaxed state EEG. Results - After the second week of age, rhythmic waves with frequencies of 6 to 9 Hz (alpha rhythm-like pattern) appeared in the EEG during the relaxed state, and were recorded in the occipital and vertex areas; duration of appearance was < 30 seconds. By use of power spectrum analysis, power distribution of the 7.5- to 10-Hz frequency band in the occipital area significantly increased after the sixth week. The high-est frequency (18 to 30 Hz) band increased in the frontal and occipital areas after the seventh week. Normalized cross-correlation coefficients at 0 time shift were > 0.6 throughout the experimental period. The normalized cross-correlation coefficients obtained from caudal interhemispheric sites increased after the second week, and were significantly greater than those in rostral sites. Conclusions and Clinical Relevance - Developmental changes in the EEG of calves during the first 10 weeks could be characterized by appearance of the alpha rhythm-like pattern and increase of the power distributions of the 7.5- to 10-Hz and 18- to 30-Hz frequency bands, which might be a useful indicator for estimating brain activity in young calves and as standard data for evaluating abnormal brain activity in calves.