In Vivo Tracing of Cortical Laminar Structure in the Rodent Olfactory System Using Manganese-Enhanced MRI (MEMRI)

Der-Yow Chen¹, Kai-Hsiang Chuang², Stephen Dodd¹, Alan Koretsky¹

MEMRI can be used for neuronal tracing in the olfactory pathway. Here it is demonstrated that MEMRI visualizes the laminar structure of the olfactory system and traces layer-specific inputs to olfactory cortices. MnCl₂ was infused into nostrils of rats which were imaged at several time points. Layers and boundaries of olfactory cortices were evident 48 h after infusion. Mn²⁺ enhancement in the superficial layer was observed earlier than the deep cell layer, consistent with known connections. Therefore, MEMRI neural tracing is specific at the level of cortical layers in the olfactory pathway, consistent with previous measurements of the somatosensory pathway.