 Alternatively strategies are transsynaptic anterograde tracers, which can cross the synaptic cleft, labeling multiple neurons within a pathway.Those can also be genetic or molecular tracers.Recently Manganese-enhanced Magnetic Resonance Imaging (MEMRI) has been used to trace functional circuits in living brains, as pioneered by Russ Jacobs, Robia Paultler, Alan Koretsky and Elaine Bearer.