Abstract
Iron deficiency (ID) is a highly prevalent nutrient deficiency that has been demonstrated to produce impairments in various aspects of perception and cognition. Animal models of ID have pointed to systematic effects on neurotransmitter synthesis and regulation, particularly with respect to dopamine, which plays a critical role in reward processing and learning. The present study tested the hypothesis that diminished iron levels would negatively affect learning and performance on a probabilistic reward task. Participants were 40 non-anemic women (hemoglobin >= 12 g/dL), 18 iron-sufficient (IS; serum ferritin > 16 μg/L) and 22 iron-deficient (ID; serum ferritin < 16 μg/L). Participants completed a version of the Iowa gambling task with simultaneous electroencephalography (EEG). In the task, there were four decks of cards, of which two were “good” (had net gain) and two were “bad” (had net loss). On each trial, they were offered the opportunity to “play” or “pass” a card from a randomly selected deck. If they chose to “play,” a monetary reward or penalty was given. Choice behavior as a function of a previous reward or penalty was examined across groups; in addition, performance was examined with respect to correlations with the iron biomarkers. Results support the hypothesis that ID & IS participants differ in response selection after penalty. ID participants more frequently chose to “play” a deck after a previous penalty from the last encounter with the deck, and serum ferritin levels were negatively related to the proportion of post-penalty “play” selections. Additionally, median reaction times when electing to “play” post-reward/penalty differed by iron status. These results suggest that ID affects responses to rewards and penalties, perhaps due to deficits in encoding contingencies or integrating previous knowledge. EEG was also examined to assess the extent to which these measures correlated with physiological indices of reward processing.
Acknowledgement: University of Oklahoma Vice President for Research