BDNF and nutritional disorder: This model allowed for precisely timed manipulation of effective TfR1-mediated iron uptake in order to identify the critical period during which rapid hippocampal development is dependent on local uptake of available iron and permitted identification of times during which iron-replenishment could and could not reverse effects of iron-deficiency on spatial learning, CA1 dendritic arborization, and genetic expression of brain-derived neurotrophic factor (BDNF), an important plasticity factor [51].