Fig. 5.

Multi-dimensional neuroanatomical tracing. A layer of immunohistochemistry is added to the tracing layer to distinguish neurochemical phenotypes. Many layers are possible. a ‘Neurochemical fingerprinting’: anterograde tracing with a suitable tracer followed by immunohistochemistry using an antibody to detect a marker inside tracer-labeled axon terminals. b Immunocytochemistry to reveal the neurochemical phenotype of retrogradely labeled neurons (in this example cholinergic neurons)