Dual activity maps in primate visual cortex produced by different temporal patterns of zif268 mRNA and protein expression.

The inducible nature of the immediate-early genes (IEGs) c-fos and zif268 allows their products to be used as activity markers in the brain. The utility of such markers in general is restricted because they can resolve only neurons activated by a single stimulus. To overcome this limitation, we have developed a double-label technique that exploits the dissimilar time course of zif268 mRNA and protein induction, allowing them to be separately induced by two different stimuli and independently stained to provide a visual display of neurons that are responsive to each stimulus. Two powerful features of this new imaging technique-the possibility of staining separate populations of activated neurons and the ability to visualize them at the cellular level-should extend IEG applications in biological activity mapping.