Spatial distribution of EEG theta activity as a function of lifetime lead exposure in 9-year-old children

The relationship between low-level childhood lead exposure and developmenta l retardation has been proposed but the existing evidence is weak. We exami ned the EEG of 42 children participating in the Mexico City, Prospective Le ad Study to determine if relative theta power and distribution across the s calp was related to history of lifetime lead exposure as measured by sequen tial blood lead concentration of the mother during pregnancy and the child after delivery. EEG was recorded from scalp electrodes placed according to the 10-20 system during eyes-closed. Theta activity (4-7 Hz) was filtered w ith a fast Fourier transform (FFT) and relative power calculated. The expec ted distribution of theta was found, with the greatest relative power centr ally located and lesser amounts at frontal, occipital, and lateral derivati ons. Multiple regression models of theta at each electrode showed that incr easing postnatal blood lead from 6 to 96 months was related to increasing r elative theta power, adjusted for age, sex and fetal suffering at delivery, in occipital derivations. The most significant increases in theta power we re associated with blood lead levels (geometric mean = 10.3 mug/dl) measure d between 54 and 72 months. Spatially weighted regression demonstrated that there was a significant antero-posterior gradient in lead-induced increase in relative theta power associated with postnatal blood lead levels at 54- 72 months and 78-96 months. The greatest lead effect on both occipital rela tive theta power and the antero-posterior gradient of theta power was found with lead at an age during which relative theta power reaches its developm ental maximum and starts to decrease. Results suggest that 54-72 months rep resent a critical period during which lead can exert lasting effects on the developmental pattern of theta activity. Occipital derivation of the large st effects of lead on theta activity may also be related to other lead-rela ted developmental deficits. (C) 2001 Elsevier Science Inc. All rights reser ved.