| Summary: | 碩士 === 國立臺灣大學 === 腦與心智科學研究所 === 101 === Polychlorinated biphenyls(PCBs) are persistent organic pollutants present in food chain and a major environmental concern due to their ubiquity, bioamplification and toxicity. In animal studies, early exposure of PCBs was associated with impairment of cognitive flexibility, working memory, inhibitory control and visuospatial learning. In epidemiological studies, prenatal PCBs exposure has been shown to have negative effect on children’s cognitive functions, including working memory, language function and attention. However, the long term effect of prenatal PCBs exposure was not ascertained due to controversial data in animal studies and short follow-up time in epidemiological studies.
An incident of mass PCBs exposure occurred in central Taiwan due to ingestion of contaminated cooking oil in 1978-1979. Previous studies had shown delayed developmental milestones and lower intelligence in children born to exposed mothers(Yucheng cohort). At ages of 6 to 16 years old, boys in this cohort had their subscales of performance IQ correlate negatively with the PCBs level of their mothers. To study the long term effect of prenatal PCBs exposure, we followed the cognitive functions with WAIS-III (Wechsler Adult Intelligence Scale, 3rd edition) in this cohort in their adult ages and also investigated neural basis of cognitive function changes with functional magnetic resonance image(fMRI) with two paradigms: a two-back task and a picture rotation task, which were related to working memory and visuospatial function, respectively.
Twenty-two young male adults (12 health control and 10 Yucheng cohort. mean age:29.2 years old) joined this study. There were no statistically significant differences in full IQ, verbal IQ, performance IQ and all of their subscales between these two groups. In the behavioral results of the two-back task and picture rotation task, no statistical significant difference was noted in the accuracy and reaction time in both of the tasks. In fMRI studies of both paradigms, the BOLD signal showed no statistical difference in the task-activating cortical area between the two groups. Comparing to the control, boys in the Yucheng cohort showed increased BOLD signal in bilateral medial frontal cortex and posterior cingulated gyrus in the two-back task but reduced signal in the similar area in the picture rotation task, indicating alteration in the task induced deactivation(TID). Reduced BOLD signal was also seen over right medial temporal lobe in the paradigm of picture rotation in the Yucheng group.
Due to the small case number, this study was not empowered to fully support the notion that prenatal PCBs exposure had long term effect on cognitive function. The findings in task related fMRI may shed light on the possible neural mechanism of the PCBs effects.
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