Using Manganese-Enhanced MRI (MEMRI) to detect the order of neuronal connections in the olfactory pathway at the level of specific layers

Introduction: It has been shown that manganese-enhanced MRI (MEMRI) can be used to perform anterograde neuronal tract tracing in a number of neural systems, including the olfactory pathway [1,2]. Furthermore, MEMRI can be used to visualize laminar structures in the olfactory pathway and cortex in vivo. Recently the layer-specific input to somatosensory cortex from thalamus and contralateral cortex could be observed if scanning occurred at the proper time intervals after Mn administration [3]. In the present study the dynamic changes of manganese enhancement has been used to detect of the order of inputs at the level of specific layers in the rodent olfactory system. Tracing to the olfactory bulb (OB), anterior olfactory neuron (AON), piriform cortex (PCx) and orbitofrontal cortex (OFC) was studied after MnCl2 was infused to nostrils or the olfactory bulb of rats. The order of estimated arrival latency followed the known anatomical connections.