Boucher et al. p = 0.003; no-go P3: r = 0.29, p < 0.001), and P3 amplitude to go trials tended to be related to greater percent correct no-go trials (r = 0.14, p = 0.051). Results from the regression analyses testing for associations between contaminants and the stimulus-locked ERP parameters are pre- sented in Table 4. Higher current blood Pb concentrations are associated with reduced P3 amplitude to go and no-go trials. When participants with current blood Pb concen- trations ≥ 5 μg/dL are excluded, this effect is still significant for no-go P3 amplitude (r = –0.24, p = 0.001; standardized β = –0.21, p = 0.007) but falls short of significance for go P3 amplitude (r = –0.16, p = 0.04; standard- ized β = –0.09, p = 0.22). The effect of current blood Pb concentrations on P3 amplitude is clearly observable when contrasting the ERP averages of the bottom and top quartiles of the distributions for current blood Pb con- centration (adjusted mean ± SD no-go P3 amplitude, 12.8 ± 7.0 μV vs . 7.8 ± 8.1 μV, Cohen’s d = –0.66; see Figure 2). The asso- ciation between cord PCB-153 and go N2 latency falls short of statistical significance after controlling for maternal age at delivery (p = 0.053), suggesting delayed N2 latency with increasing prenatal exposure. Analyses with Hg revealed an association between cur- rent blood Hg concentrations and reduced P3 amplitude in the go condition that fell short of statistical significance after controlling for confounders (p = 0.052). Cord blood Hg and current plasma PCB-153 concentrations levels were not significantly associated with any of the stimulus-locked ERPs. Interaction terms revealed significant inter- actions between current Pb and current Hg on P3 amplitude elicited in the go condition (standardized β = 0.15, p = 0.04) and between current Pb and current PCB-153 on P3 amplitude elicited in both the go (standard- ized β = 0.17, p = 0.02) and the no-go (stan- dardized β = 0.13, p = 0.08) conditions. In all cases, the Pb effects were stronger in children with lower coexposures to the other chemi- cals. There were also significant interactions ERP parameter N2 (Fz) Go latency No-go latency Go amplitude No-go amplitude P3 (Pz) Go amplitude No-go amplitude r –0.01 –0.03 0.03 –0.00 –0.06 –0.06 β 0.08a,b –0.01d,e,f,g,h 0.08j,k 0.02a,f,j,k,l,m –0.05c,h,l –0.06a,g,l,p Pb r 0.05 0.01 0.02 0.00 –0.20* –0.26* between cord Hg and cord PCB-153 on no-go N2 latency (standardized β = 0.16, p = 0.05) and no-go P3 amplitude (standard- ized β = –0.20, p = 0.02). Stratification analy- ses revealed that higher cord Hg resulted in slower no-go N2 latency, and smaller no-go P3 amplitude in children with higher pre- natal PCB exposure, but higher no-go N2 amplitude only in children with lower prenatal PCB exposure. Response-locked ERPs. Repeated-measures ANOVAs with response type (correct go, incorrect no-go) as a within-subject variable revealed significant error-related effects on mean amplitude during the ERN [fronto- central electrode (FCz): 0.3 vs. –4.0 μV; +5 0 –5 +5 V 0 µ –5 +5 0 –5 Go Go 1st blood Pb quartile 4th blood Pb quartile No-go No-go Fz Cz Pz Table 4. Associations between contaminants and stimulus-locked ERP components recorded during the go/no-go task (n = 193). Cord blood Current blood Cord plasma Current plasma Cord blood Current blood Values are Pearson correlation (r) and standardized regression (β) coefficients from multiple regression analyses. Negative (–) associations with N2 amplitude indicate greater (more negative) amplitude. Superscripts (a–p) indicate control variables included in the final model for each of the regression analyses. aMaternal age. bCord PCB-153. cTime at assessment. dChild age. eAdoption status. fMaternal binge drinking during pregnancy. gBreast-feeding duration. hChild Hg. iChild PCB-153. jCord DHA. kMaternal Raven’s score. lMaternal smoking during pregnancy. mChild sex. nTransported from a remote village. oChild Pb. pCord Hg. *p < 0.01. **p < 0.05. #p < 0.10. 612 ovlume 120 | number 4 | April 2012 • Environmental Health Perspectives –100 0 200 400 600 800 1,000 ms Figure 2. Grand average for stimulus-locked go/no-go ERPs at midline electrodes comparing participants from the first quartile of blood Pb concentrations at time of testing (range, 0.4–1.3 μg/dL; n = 47; thin lines) and those from the fourth quartile (range, 2.9–12.8 μg/dL; n = 48; thick lines) for go (solid lines) and no-go (dashed lines) trials. The N2 is the second negative component (~ 375 msec), which is more pronounced at the frontal lead (Fz). The P3 peaks around 500 msec and is larger at the parietal lead (Pz). Children with higher blood Pb concentrations show reduced activity during the P3 time window compared with children with lower Pb levels. PCB-153 β 0.02b,c –0.01d,f,g,h 0.02d,j,k 0.05j,k,l,m –0.16**h –0.23*h r 0.09 0.01 –0.03 –0.05 0.03 0.04 β 0.15#a –0.11d,f,g,h 0.00d,j,k –0.01a,f,j,l,m 0.08c,h,l,n,o 0.12a,l,o,p r 0.05 0.14# 0.01 0.04 –0.13# –0.13# β 0.08a,c 0.01e,f,h 0.07d,j 0.01a,f,j,k,l,m –0.01c,h,l,n,o –0.01a,l,o,p r 0.08 0.09 0.09 0.02 –0.08 –0.14# β 0.05a,b 0.04d,e,f,g,i 0.13#d,j 0.03a,f,j,k,l,m –0.02i,l,n,o –0.10a,g,l,o Hg r 0.01 0.16** 0.01 0.04 –0.21* –0.18** β 0.02a,c 0.11d,f 0.06d,j,k 0.02a,f,j,k,l,m –0.15#n,o –0.06a,g,i,l,o