Viral neuronal tracing is the use of a virus to trace neural pathways, providing a self-replicating tracer. Viruses have the advantage of self-replication over molecular tracers but can also spread too quickly and cause degradation of neural tissue. Viruses that can infect the nervous system, called neurotropic viruses, spread through spatially close assemblies of neurons through synapses, allowing for their use in studying functionally connected neural networks.[1][2][3]
The use of viruses to label functionally connected neurons stems from the work and bioassay developed by Albert Sabin.[4] Subsequent research allowed for the incorporation of immunohistochemical techniques to systematically label neuronal connections.[4] To date, viruses have been used to study multiple circuits in the nervous system.