Cellular-resolution activity mapping of the brain using immediate-early gene expression

Immediate-Early Genes are a class of genes that are rapidly up-regulated following neural stimulation. Due to their quality as potential activity markers in the CNS, they have been used extensively in functional mapping studies. At least three genes have been popularly used, including zif268 (Egr1, NGFI, Krox-24, or ZENK), c-fos and recently, Arc. A number of techniques have been developed in applying IEG labelling for the development of functional maps, thus overcoming some of the earlier limitations of this approach. Current developments highlight the future prospects of cellular-resolution functional activity mapping of the brain.