Fig. 6

The effect of lead on short-term spatial memory in the NOL test. The NOL test was performed before, during, and after the lead exposure to assess for spatial working memory deficits. The time animals spent investigating the object in the old (location A) vs. new (location C) locations was quantified. More time spent exploring the object in the novel vs. old location indicates memory for the old location. ( A ) All the animals had intact spatial memory prior to the lead exposure. ( B ) At 7 weeks into the lead exposure, only the lead-treated ApoE4-KI females did not discriminate between the old vs. new object locations (Two-tailed t-test (A vs. C): p = 1.000). ( C ) At 11 weeks, both the lead-treated ApoE4-KI females and males no longer discriminated between the object locations (females, p = 0.4042; males, p = 0.1959) while the ApoE3-KI females and males spent significantly more time exploring the novel object location (females, p = 0.0107; males, p = 0.0098). ( D ) Lead-treated ApoE4-KI females and males continued to exhibit a deficit in spatial working memory at 10 months post-lead exposure (females, p = 0.0961; males, p = 0.1855). Lead-treated ApoE3-KI mice still spent statistically significantly more time exploring the novel object location at 10 months post-lead exposure (females, p = 0.0186; males, p = 0.0320). Data are mean ± SEM with n = 8–13 per genotype/treatment. Two-tailed t–test: n.s. not significant, * p < 0.05; ** p < 0.01; *** p < 0.001