Timing of iron deficiency and recognition memory in infancy

ABSTRACT

Objective: To determine the relationship between iron deficiency (or iron-deficient, ID) and neural correlates of recognition memory depending on ID timing (gestation vs. infancy) and infant age at testing (9 vs. 18 months).

Study design: Event-related potentials (ERP) were used in a visual recognition memory task (mother vs. stranger face) to compare healthy term infants according to iron status at birth and 9 months. Fetal-neonatal ID was defined as cord serum ferritin < 75 µg/l or zinc protoporphrin/heme ratio > 118 µmol/mol, postnatal ID as ≥ 2 abnormal iron measures at 9 months with normal cord-blood iron status, and iron-sufficient as not ID at birth or 9 months. Recognition of mother faces was measured by negative component (Nc) and late slow wave (LSW). These ERP components reflect attention and memory updating processes, respectively.

Results: All groups showed differences in Nc amplitude elicited by mother and stranger faces at 9 months. At 18 months, only postnatal ID and iron-sufficient groups showed condition differences in Nc amplitude. However, the 2 groups were different in the involved brain regions. For LSW, only the 2 ID groups showed condition differences in amplitude at 9 months. At 18 months, condition differences were not observed in any group.

Conclusions: This study indicates that the timing of ID in early life (fetal-neonatal vs. postnatal) modulates the impact of ID on recognition memory. Such impact also varies depending on the age of infants at testing (9 vs. 18 months).

KEYWORDS:

• Infancy
• fetal-neonatal iron deficiency
• postnatal iron deficiency
• recognition memory
• event-related potentials

Acknowledgements

We thank the participants and their families and Yaping Shi, Liqin Chen, Zheng Shen, Zhengyan Zhao, Mingyan Li, Chai Ji, Zhiwei Zhu, and other team members for assistance with subject enrollment, data collection, and laboratory analyses.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data that support the findings of this study are available from the corresponding author, FG, upon reasonable request.

Additional information

Funding

This study was supported by grants from the National Institutes of Health (P01HD039386, to BL) and the National Natural Science Foundation of China (no. 81273085, to JS). ERP analyses were conducted during FG’s post-doctoral fellowship at the University of Michigan.

Notes on contributors

Fengji Geng

Fengji Geng is affiliated to the College of Education at Zhejiang University. Her research focuses on developmental cognitive neuroscience. Specifically, she studies how nutritional deficiency and environmental pollutions affect cognitive development and brain maturation during childhood.

Xiaoqin Mai

Xiaoqin Mai is a professor at Department of Psychology, Renmin University of China. As a developmental cognitive neuroscientist, she focuses on how nutritional deficiency affects the development of children's brain and behavior.

Jianying Zhan

Jianying Zhan is a pediatrician at the Children's hospital affiliated to Zhejiang University School of Medicine. Her research focuses on the early development of children, especially on cognitive development.

Lin Xu

Lin Xu is an Attending Physician in the Department of Child Health Care at the Children's Hospital Zhejiang University School of Medicine. As a developmental-behavioral pediatrician, she studies the effect of nutrition and environmental problems on children's behavior.

Michael Georgieff

Michael K. Georgieff is the Martin Lenz Harrison Land Grant Professor of Pediatrics at the University of Minnesota where he is executive vice-chair of Pediatrics and Director of the Center for Neurobehavioral Development. He has published over 200 papers on the effect of nutrient deficiencies on the developing brain.

Jie Shao

Jie Shao is Chief Doctor, Director of the Department Child Health Care at Children's hospital, Zhejiang University School of Medicine. As a developmental-behavioral pediatrician, she studies common nutritional and environmental problems that adversely affect children's early development. Her research focuses on the effect of iron deficiency on the development of brain and behavior.

Betsy Lozoff

Betsy Lozoff is University of Michigan Professor Emerita (Pediatrics, Medical School; Environmental Health Sciences, Public Health). As a developmental-behavioral pediatrician, she studies common nutritional and environmental problems that adversely affect children's development, especially in resource-poor settings. Her specific focus is brain and behavioral effects of iron deficiency in infancy.