Each participant underwent fMRI while performing two tasks to measure the brain's executive functioning, which governs attention, decision making and impulse control. The imaging revealed that in order to complete a task that required inhibition, those with increased blood lead levels required activation from additional regions within the frontal and parietal lobes of the brain.
"This tells us that the area of the brain responsible for inhibition is damaged by lead exposure and that other regions of the brain must compensate in order for an individual to perform," Dr. Cecil said. "However, the compensation is not sufficient."
Imaging performed during a second task designed to test attention revealed an association between higher lead levels and decreased activation in the parietal region and other areas of the brain.
According to Dr. Cecil, the brain's white matter, which organizes and matures at an early age, adapts to lead exposure, while the frontal lobe, which is the last part of the brain to develop, incurs multiple insults from lead exposure as it matures.
"Many people think that once lead blood levels decrease, the effects should be reversible, but, in fact, lead exposure has harmful and lasting effects," she said.
Dr. Cecil believes that these findings lend support to previous reports from the Cincinnati Lead Study showing that the lasting neurological effect of lead exposure, rather than a poor social environment, is a key contributor to the subsequent cognitive and behavior problems in this group.
|Contact: Linda Brooks|
Radiological Society of North America