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Michael Wenger, Laura Murray-Kolb, Jere Haas; Energy expended in encoding and retrieval in a visual memory task: Interactive effects of workload and body iron status. Journal of Vision 2013;13(9):13. doi: https://doi.org/10.1167/13.9.13.
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Iron deficiency (ID), with and without anemia, has been shown to have deleterious effects on physical performance. Animal models have demonstrated that physical endurance and the concentrations of oxidative enzymes and respiratory proteins all decrease in ID, even at levels that do not reach the point of anemia. Human studies have documented reductions in endurance in ID without anemia, with effects being seen in measures of energy expenditure and work efficiency. The present effort extends the examination of the effect of ID to consideration of its effects on energy use in the performance of perceptual and cognitive work in the context of a visual memory task. ID women (ferritin <16 g/dl, n = 20) and age-, education- and activity-level-matched controls (n = 17) provided blood samples for measures of iron status; completed a set of questionnaires probing general health and activity levels, menstrual status, and consumption of iron-rich foods; completed a working memory task (as a general measure of cognitive efficiency); and performed a visual Sternberg task with a concurrent mental math task. While performing the visual Sternberg task, participants' brain and metabolic states were measured using electroencephelography (EEG) and measures of the volume of O2 and CO2 in expired air, respiratory rate, and heart rate. We consider here effects of variations in workload during both encoding and retrieval. We show statistically significant relationships among behavioral, EEG, and metabolic measures, all as a function of variations in task difficulty and iron status, with lower iron status being associated with lower levels of behavioral performance and diminished potential for beginning and sustaining work. The data suggest the potential for using EEG for indirect estimation of the effects of ID on brain energy expenditure.
Meeting abstract presented at VSS 2013
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