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Chronic low-lead exposure from birth produces deficits in discrimination reversal in monkeys
Insights
Lead exposure in infant cynomolgus monkeys (Macaca fascicularis) caused cognitive deficits in discrimination reversal tasks. Higher lead levels resulted in more significant impairments, particularly in form discrimination, persisting into adulthood.
Area of Science:
- Neuroscience
- Toxicology
- Primate Research
Background:
- Lead exposure in early development is a significant public health concern.
- Understanding the long-term neurodevelopmental effects of lead is crucial for risk assessment.
- Primate models offer valuable insights into human brain development and lead toxicity.
Purpose of the Study:
- To investigate the long-term cognitive effects of early-life lead exposure in cynomolgus monkeys.
- To assess the impact of different blood lead concentrations on learning and reversal tasks.
- To determine if lead-induced deficits persist into later developmental stages.
Main Methods:
- Cynomolgus monkeys were dosed from birth with varying levels of lead (100, 50, 0 µg/kg/day).
- Blood lead concentrations were monitored throughout the study.
- At approximately 3 years of age, monkeys were tested on three nonspatial discrimination reversal tasks.
Main Results:
- The higher lead dose group showed significant impairments across all tasks compared to controls.
- Deficits were most pronounced in form discrimination tasks and during initial reversal learning.
- The lower lead dose group exhibited impairments in color discrimination and later reversals.
Conclusions:
- Early-life lead exposure leads to persistent cognitive deficits in discrimination reversal learning in primates.
- The severity of cognitive impairment correlates with the level of lead exposure.
- These findings highlight the critical need for minimizing lead exposure during early development.
Abstract:
Cynomolgus monkeys (Macaca fascicularis) were dosed from birth with 100, 50, or 0 micrograms/kg/day of lead. This protocol resulted in blood lead concentrations of 25, 15, or 3 micrograms/dl, respectively, before withdrawal of infant formula at 200 days of age. Blood lead concentration declined thereafter over the next 100 to 150 days to steady-state levels of 13, 11, or 3 micrograms/dl. At approximately 3 years of age, monkeys were tested on a series of three discrimination reversal tasks: nonspatial form discrimination, nonspatial color discrimination with irrelevant form cues, and nonspatial form discrimination with irrelevant color cues. The higher dose group was impaired relative to controls over the entire experiment (all three tasks combined), the two form discrimination tasks combined, and the form discrimination with no irrelevant cues. Deficits were most marked over the first several reversals. The lower dose group was impaired on the color discrimination task and on the last several reversals of all tasks combined. In addition, the higher dose group was impaired relative to the lower dose group over the entire experiment.